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WO1996002276A9 - Nouveaux reseaux de gel polymere et procedes d'utilisation - Google Patents

Nouveaux reseaux de gel polymere et procedes d'utilisation

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Publication number
WO1996002276A9
WO1996002276A9 PCT/US1995/009815 US9509815W WO9602276A9 WO 1996002276 A9 WO1996002276 A9 WO 1996002276A9 US 9509815 W US9509815 W US 9509815W WO 9602276 A9 WO9602276 A9 WO 9602276A9
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WO
WIPO (PCT)
Prior art keywords
polymer
polymer gel
gel network
network
acid
Prior art date
Application number
PCT/US1995/009815
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English (en)
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WO1996002276A2 (fr
WO1996002276A3 (fr
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Priority to AU32748/95A priority Critical patent/AU3274895A/en
Publication of WO1996002276A2 publication Critical patent/WO1996002276A2/fr
Publication of WO1996002276A9 publication Critical patent/WO1996002276A9/fr
Publication of WO1996002276A3 publication Critical patent/WO1996002276A3/fr

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Definitions

  • volumetric change phenomena have been observed in three-dimensional, permanently crosslinked polymer gel networks.
  • an external environmental condition e.g. temperature; solvent composition; pH, electric field; light intensity and wavelength; pressure, ionic strength
  • the polymer gel network contracts and/or expands in volume.
  • the volume of such a gel may, under certain circumstances, change reversibly by a factor as large as several hundred when the gel is presented with a change in external conditions (i.e. the gel is a "responsive" gel; see, for example, Tanaka Phys. Rev. Lett. 40: 820, 1978; Tanaka et al. Phys. Rev. Lett. 38:771, 1977; Tanaka et al. Phys. Rev. Lett. 45:1636, 1980;
  • Yet another object of the invention is to provide improved controlled- release delivery systems in which safe, responsive gels are utilized to deliver a substance to an environment.
  • One embodiment of the invention is a crosslinked, responsive polymer gel network comprising polymer chains interconnected by way of multifunctional crosslinker.
  • the polymer chains and crosslinker have a known acceptable toxicologicai profile, hereinafter "KATP".
  • Another embodiment is a crosslinked, responsive polymer gel network comprising polymer chains interconnected by way of a KATP crosslinkages.
  • a third embodiment of the invention is a crosslinked, responsive polymer gel network comprising polymer chains interconnected by way of a crosslinker, in which each of the polymer and crosslinker is obtainable from a precursor that is used in a process for making a material that has a KATP.
  • the gels have the characteristic that, when leached, the leachate from the network also has a KATP as well as any residual elements in the network.
  • the gel solvent also may have a KATP.
  • a preferred responsive polymer gel network are polysaccharide chains crosslinked with a multifunctional carboxylic acid obtainable from an acyl halide derivative of said acid.
  • the preferred polymer chains are polysaccharides (e.g. starch or cellulose ethers) and the preferred multifunctional carboxylic acid is selected from the group consisting of adipic acid, sebacic acid, succinic acid, citric acid, 1,2, 3,4- butanetetracarboxylic acid, and 1,10 decanedicarboxylic acid.
  • Particularly preferred polymers are cellulose ethers selected from the group consisting of hydroxyethylcellulose, hydroxypropylcellulose, and hydroxypropylmethylcellulose.
  • the responsive polymer gel networks of the present invention may be responsive to any of a variety of triggers such as temperature or pH.
  • the pH-response may be triggered by a change in ion concentration, solvent concentration, electric field, magnetic field, electromagnetic radiation, or mechanical force.
  • Methods for making crosslinked polymer networks include selecting a polymeric starting material capable of being crosslinked, wherein the polymeric starting material selected for the particular use has a known acceptable toxicologicai profile for the particular use or for a related use; selecting a crosslinker capable of crosslinking the polymeric starting material, wherein the crosslinker selected for the particular use has a known acceptable toxicologicai profile for the particular use or for a related use; and contacting the crosslinker and polymeric starting material under conditions sufficient to form the three- dimensional, crosslinked polymer network.
  • Another method involves selecting a crosslinker capable of crosslinking the polymeric starting material, so that the resulting network, after formation, contains a crosslinkage that has a known acceptable toxicologicai profile.
  • Preferred methods include the steps of contacting a crosslinker comprising an acyl halide derivative of a multifunctional carboxylic acid with a polysaccharide under conditions sufficient for the three-dimensional, polymer gel network to form so that the gel network includes polysaccharide chains crosslinked with the acid.
  • Particularly preferred method use a polysaccharide selected from the group consisting of starch and cellulose ethers, which group includes, for example, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, and modified food starch.
  • Preferred methods use a crosslinker that is an acyl halide derivative of a multifunctional carboxylic acid, such as, for example, an acyl halide derivative of adipic acid, sebacic acid, succinic acid, 1,2,3,4- butanetetracarboxylic acid, or 1,10 decanedicarboxylic acid.
  • Other preferred methods use dialdehyde crosslinkers such as, for example, glutaraldehyde.
  • Still other preferred methods utilize irradiation energy as a crosslinker.
  • a KATP polymer gel network of the invention capable of incorporating the substance from a solution containing the substance is introduced into the solution and a volumetric change of the gel is induced by changing an environmental condition to which the gel is exposed so that the gel incorporates the substance and separates the substance from the solution.
  • a further method includes introducing a KATP polymer gel network of the invention that is capable of excluding a substance from a solution containing the substance. The gel is induced to undergo a volumetric change by changing an environmental condition to which the network is exposed so that the network disgorges the substance to the environment of use.
  • a method of delivering a substance into an environment of use includes the steps of incorporating the substance into the KATP polymer network of the invention and inducing a volumetric change in the network by changing an environmental condition to which the network is exposed so that the network disgorges the substance to the environment of use.
  • a method for removing a substance from an environment containing a the substance includes introducing into the environment a KATP polymer network of the invention that contains a ligand reactive with the substance when the ligand is exposed to the substance and changing an environmental condition of the network to cause a volumetric change and expose the ligand to the substance, so that the substance is incorporated into the gel.
  • a method of loading a solute into a KATP polymer gel network includes contacting the solute with the KATP gel, a second polymer, and a salt under conditions sufficient for the solute to selectively partition into the first polymer.
  • a cosmetic composition, wound dressing, pharmaceutical composition, monitoring electrode; adhesive device, iontophoretic device; dialysis device; including the KATP polymer network are also intended to be encompassed within the scope of the invention.
  • the KATP responsive gel networks of the invention have the singular advantage of having toxicologicai profiles which are more readily evaluated than prior art responsive gels.
  • the present responsive gels may be used as environmentally benign materials which may be easily recycled for many commercial purposes and which may be used in the human body, or in the body of a non-human animal.
  • the present invention therefore provides novel pharmaceutical compositions, comprising a KATP polymer gel network (also termed a "safe" polymer gel network) and an effective amount of a biologically active compound.
  • the present invention also provides controlled-release delivery devices for controlled delivery of a biologically active compound into a biological environment.
  • the KATP polymer gel networks of the present invention are also useful for coating materials, such as medical devices, and the invention encompasses such coated devices.
  • a polymer gel network comprising a polycation and a polyanion interacting to form a polyelectrolyte complex is formed on at least a portion of a surface of the device.
  • Biologically active compounds can be loaded into such coated devices, and in some embodiments an encapsulator is provided that traps the biologically active compound within the polymer gel network.
  • the encapsulator comprises a KATP polymer
  • the invention essentially provides a safe polymer gel network coating on an existing safe polymer gel network. Methods of coating medical instruments, and of loading biologically active compounds into or delivering biologically active compounds from, such coated instruments, are also provided.
  • Figure 1 is a pH-volume relationship for a crosslinked HPC gel of the invention.
  • Figure 2 is a pH-volume relationship for a crosslinked modified food starch gel of the invention.
  • FIG. 3 presents depictions of present-day osmotically-controlled oral delivery systems.
  • Figure 4 depicts formation of a safe polymer gel comprising polyelectrolyte complexes on a polyamide device.
  • Figure 5 depicts radiation-induced grafting of a safe polymer gel comprising polyelectrolyte complexes onto low density polyethylene.
  • Figure 6 depicts coating of a safe polymer gel comprising polyelectrolyte complexes onto a porous support.
  • Figure 7 depicts coating of a safe polymer gel comprising polyelectrolyte complexes onto a polypropylene membrane.
  • the materials of the present invention are three-dimensional, permanently crosslinked polymer networks.
  • a "polymer network” is that three-dimensional structure resulting from the crosslinking of polymers.
  • Preferred polymers are chemicaUy-crosslinked.
  • “Chemically crosslinked” means that a multifunctional chemical reagent is added during synthesis which reacts with, and interconnects via covalent bonding, two or more polymer chains.
  • chemically crosslinked is not meant to include gamma radiation, photochemical, electron beam, or ultraviolet crosslinking when these methods are intended to replace a chemical moiety used as a crosslinker.
  • direct crosslinking of hydroxypropyl cellulose with itself using radiation is not intended to be included within the scope of this invention.
  • the multifunctional chemical reagent is the "crosslinker".
  • the form that the crosslinker takes once the polymer network has been formed is defined as the "crosslinkage”.
  • succinyl chloride is a crosslinker that may not have a KATP but, once it is reacted in solution and crosslinked, it converts to succinic acid crosslinkage which does have a KATP. It will be understood by those having ordinary skill in the art that, not every single crosslinking reaction will produce the desired KATP crosslinkage; some defects may arise.
  • gels of the present invention have crosslinkages that all have a KATP, although the starting material crosslinker (e.g. precursor acyl halide derivative) may not have a KATP.
  • polymer chains themselves may have impurities or other imperfections that are considered to be within tolerance requirements for materials of this type when used for the particular purposes of the present invention.
  • gels of the present invention all have a KATP.
  • the preferred three-dimensional polymer networks are homogeneous or microporous gels.
  • gel refers to materials between the liquid and solid state containing enough solvent molecules to cause macroscopic changes in the sample dimension.
  • the term “gel” also includes polymer gel networks in which virtually all liquid (i.e., solvent) has been driven off, leaving a “dry” gel.
  • microporous refers to two-phase systems of a continuous solid phase containing numerous pores filled with fluid.
  • a "microstructure” as defined herein, refers to those structures of a gel (e.g. pores, voids, walls and the like) observable under a scanning electron, or other, microscope and ranging in size from 0.01 to about 100 microns.
  • Gels containing pores in the size range 0.01 to about 10 microns are 'microporous'. If some of the pores are interconnected, the gel is typically called an "open-cell" gel. If all the pores in the gel are interconnected to each other, the gel is a "bicontinuous" gel. If the pores are discrete (not connected to each other), so that the internal space of each pore is independent of the other pores, the gel is a "closed-cell” gel.
  • the present invention encompasses as all these mo ⁇ hological forms and combinations of these forms. Microporous responsive gels may be "fast response" gels.
  • fast response means that the gel reaches 90% of its maximum volumetric swelling or 90% of its ininimum volumetric collapse in a time that is at least ten times faster than a comparable non-porous gel of the same geometry when both gels are subjected to a similar change in an environmental condition.
  • the polymer gel network materials described herein may also be employed in a variety of forms.
  • the materials may be used as films or membranes, tubes, hollow fibers, solid fibers, molded objects, solid particles, capsules, micelles or liposome-like structures. They may also be applied as coatings on solid surfaces (e.g. catheter tips) or in the pores of porous solids, as solutions, paniculate suspensions and the like. Coatings may be applied to and/or attached to polymers, metals, ceramics, glasses, carbons and the like.
  • KATP toxicologicai profile
  • This term refers to the ability of a given polymer gel network or component thereof to successfully pass regulatory approval by an appropriate governmental body or industry group responsible for the safety of drugs, cosmetics, medical devices, pharmaceuticals, food additives, food processing and the like when the drugs, cosmetics, medical devices, pharmaceuticals, food additives, food processing and the like, are used in animals, including humans. More particularly, and at least in the United States, a polymer network of the present invention is considered to have a KATP if the network, and its polymer/crosslinker components, are considered by the U.S. Food and Drug Administration ("U.S.
  • materials that are considered to have an KATP suitable for the present invention include those on the "Generally Regarded as Safe” (GRAS) list promulgated by the Food and Drug Admmistration at 21 C.F.R.182.1-182.8997, when used for the purpose indicated in accordance with good manufacturing practices.
  • GRAS materials useful in forming crosslinked polymer networks of the invention include methylcellulose (21 C.F.R. 182.1480); adipic acid (21 C.F.R. 184.1009) and succinic acid (21 C.F.R. 184.1091).
  • Other materials that are considered to have a KATP are those that are permitted for direct consumption as food additives (amino acids- 21 C.F.R.
  • binders/fillers film forming agents and thickeners for food
  • film forming agents and thickeners for food such as ethylcellulose (21 C.F.R. 172.868); hydroxypropylcellulose (21 C.F.R. 172.870); methyl ethylcellulose (21 C.F.R. 172.872); and hydroxypropylmethylcellulose (21 C.F.R. 172.874); modified food starch (21 C.F.R. 172.892).
  • Materials suitable for treating, processing, or packaging food are also considered to have a KATP under the design pathways described herein.
  • Exemplary substances include: polyvinylpyrrolidone (21 C.F.R. 173.55); adipic acid, fumaric acid, sebacic acid, and maleic acid (21 C.F.R. 175.300 (b) (vii) (a)) ; carboxymethylcellulose, ethylcellulose, ethyl hydroxy ethylcellulose, hydroxypropylmethylcellulose, and methyl cellulose (21 C.F.R. 175.300 (b) (xvi)).
  • the polymer gel in its crosslinked form must have an aqueous leachate that has a KATP or the aqueous leachate must contain residual moieties (i.e. materials left over from synthesis) such that the solvent is within acceptable limits promulgated by the appropriate regulatory body such as the U.S. FDA. FDA test procedures for determining leachates and residuals from polymeric coatings may be found in 21 C.F.R. 175.300 (Table 2).
  • surfactants such as diethanolamide condensates, n-alkyl (C 8 -C lt ) amine acetates, and di-n-alkyl (Cg-Cig) dimethyl ammonium chloride (21 C.F.R. 172.710).
  • Pathway Number 1 The individual polymer precursors), the crosslinker used in the synthesis, the final three-dimensional polymer network that is to be used in a particular context (e.g. food separation, drug release, medical devices, cosmetics) and, optionally, the liquid solvent incorporated within a polymer network, must all have a KATP for that particular use or must have a KATP for a related use.
  • Pathway Number 2 This pathway concerns the methods for making desirable KATP polymer gels.
  • the polymer and crosslinker precursors and any processing aids (i.e. surfactants, anti-foaming compounds, and the like) used in synthesis of a KATP gel must also be used in processes for making other materials that have a KATP for the same, or for a related use.
  • processing aids i.e. surfactants, anti-foaming compounds, and the like
  • a polymer network falling within any single pathway, or any combination of pathways, is suitable and is intended to be encompassed within the scope of the invention.
  • HPC HPC
  • HPC HPC
  • HPC HPC
  • adipic acid both HPC and adipic acid have KATP's for use as food additives (21 C.F.R. 172.870), thus satisfying Pathway 1.
  • adipoyl chloride may be used in the synthesis of the adipic acid crosslinkage (see Pine et al. Organic Chemistry, McGraw-Hill, p. 319, 1980 and Example 1, infra).
  • Adipoyl chloride is used in the production of commercial penicillins (see, for example, Laubeck et al. J. Chrom. Sci. 14, 1976), which is consistent with Pathway 2.
  • an aqueous leachate from a polymer gel consisting of HPC crosslinked with adipic acid would be adipic acid and or the cellulose ether (both KATP materials).
  • Cellulose ethers i.e., hydroxypropylcellulose-HPC
  • Cellulose ethers are suitable as polymer backbones since they have a KATP when used for food additives (Aqualon Product Data, supra).
  • Cellulose ethers may be crosslinked with adipic acid and both HPC and adipic acid have KATP's for use as food additives (see above), thus satisfying Pathway 1.
  • adipoyl chloride may be used in the synthesis of the adipic acid crosslinkage (see above), thus satisfying Pathway 2.
  • an aqueous leachate from a polymer gel consisting of HPC crosslinked with adipic acid would be adipic acid and/or cellulose ether.
  • Cellulose ethers i.e. hydroxypropylcellulose-HPC
  • Cellulose ethers are suitable as polymer backbones since they have a KATP when used for food additives (Aqualon Product Data, supra).
  • Cellulose ethers may be crosslinked with adipic acid and both HPC and adipic acid have KATP's for use as food additives (see above), thus satisfying pathway 1.
  • Surfactants such as diethanolamide condensates, n-alkyl (-C 8 -C lg ) amine acetates, and di-n-alkyl (C 8 -C 18 ) dimethyl ammonium chloride (21 C.F.R. 172.710), suitable for use with pesticides, may be added to the gel, satisfying Pathway 2 that starting materials may be used in processes for making other KATP materials.
  • Polymeric starting materials most suitable for the present networks are crosslinkable materials polymerized via peptide bonds, phosphate ester bonds and ether bonds.
  • Exemplary polymers are natural product polymers derived from a living organism (i.e, of algal, microbial, animal, plant origin).
  • Exemplary algal natural polymers include agar, furcelleran, alginate, carageenan.
  • Exemplary plant natural polymers include starch, cellulose, pectin, gum arabic, guar gum, tracaganth, ghatti seed gums, locust bean gum.
  • Exemplary microbial polymers include xanthan, pullalan, dextran, gellan.
  • Exemplary animal polymers include chitin, chitosan, guar, heparin, hyaluronic acid and collagen.
  • KATP materials that include water-soluble, linear polymers such as polysaccharides (e.g. cellulose, food starch-modified (21 C.F.R. 172.892), chitin, chitosan, hyaluronic acid, xanthan gum (21 C.F.R. 172.695), chondroitin sulfate, heparin, and the like) and hydroxyalkyl, alkylhydroxyalkyl and alkyl-substituted cellulose derivatives such as cellulose ethers.
  • polysaccharides e.g. cellulose, food starch-modified (21 C.F.R. 172.892), chitin, chitosan, hyaluronic acid, xanthan gum (21 C.F.R. 172.695), chondroitin sulfate, heparin, and the like
  • hydroxyalkyl, alkylhydroxyalkyl and alkyl-substituted cellulose derivatives such as
  • Exemplary cellulose ethers include methylcellulose (MC), hydroxyethylcellulose (HEC), ethylhydroxyethylcellulose (EHEC), hydroxyethylmethylcellulose (HEMC), hydroxypropylmethylcellulose (HPMC), hydroxypropylcellulose (HPC), carboxymethylcellulose (CMC), and hydroxymethylcellulose (HMC).
  • Cellulose ethers suitable for use in the present invention are readily available under a variety of trade names from a variety of manufacturers, for example: MC ("Methocel A”- Dow Chemical Company; “Metulose SM”- Shinetsu Chemical Company); HPMC ("Methocel E”- Dow Chemical Company; “Celacol HPM”- British Celanese Ltd.); HEC ("Cellosize WP”- Union Caibide Corporation); HPC (Aqualon Inc.).
  • Polynucleotides such as ribo- and deoxyribonucleotides are also suitable for crosslinking according to the invention.
  • Responsive polymers suitable for synthesis of KATP networks may also be KATP synthetic polymers such as polyethylene glycol (PEG)- e.g. 21 C.F.R. 172.210, 172.770, 172.820, 173.310; polyvinylalcohol (PVA- 21 C.F.R. 175.300 (xv)); polyethylene oxide (21 C.F.R. 172.770) and the like.
  • PEG polyethylene glycol
  • PVA- 21 C.F.R. 175.300 (xv) polyethylene oxide
  • 21 C.F.R. 172.770 polyethylene oxide
  • Crosslinkers are those chemical reagents with suitable KATP that are capable of linking polymer backbones. Specific crosslinkers will depend upon the polymer but preferred crosslinkers for polysaccharides, especially modified food starches and cellulose ethers, are multifunctional carboxylic acids, such as adipic acid (hexanedioic acid: HOOC CH ⁇ COOH), succinic acid (HOOC(CH 2 ) 2 COOH), malonic acid (propanedioic acid: CH 2 (COOH) 2 ), sebacic acid (decanedioic acid: HOOC(CH 2 )COOH), glutaric acid (pentanedioic acid: HOO CH ⁇ COOH), or any dicarboxylic acid (e.g.
  • adipic acid hexanedioic acid: HOOC CH ⁇ COOH
  • succinic acid HOOC(CH 2 ) 2 COOH
  • malonic acid propanedioic acid: CH 2 (COOH) 2
  • Dicarboxylic hydroxyacids such as tartaric acid and malic acid may also have suitable KATPs, as may multifunctional carboxylic acids such as 1,2,3,4-butanetetracarboxylic acid.
  • KATPs include dialdehydes, such as glutaraldehyde, which are preferably utilized in an acidic environment. Irradiation energy is another useful crosslinker with a suitable KATP.
  • esterification reactions between the hydroxyl groups of the ether and the carboxyl group on the preferred crosslinkers provides the crosslinkage arrangement. It will be further understood that certain ethers will participate in more active crosslinking than others. We have found that adipic acid will not produce a useful crosslinkage with HPC and HPMC while it will crosslink HEC. This is probably due to the stearic hindrance to esterification of the crosslinker afforded by the secondary and tertiary alcohols of HPC and HPMC, as opposed to the less sterically hindered primary alcohols of HEC.
  • Unsaturated dibasic acids have been used to physically crosslink water soluble polymers by application of drying and/or heat (see, for example, Reid U.S. Patent 3,379,720, incorporated herein by reference).
  • the heat required to crosslink water soluble polymers within a reasonable time of several hours is very high, ranging from 90° C (2-3 hour gelation) to 200° C (1-2 minute gelation). This may render the Reid method unsuitable for use with heat labile, biologically active compounds.
  • the Reid methodology produced a gel in 10-30 days.
  • acyl halide derivatives of multifunctional carboxylic acids as the crosslinker reagents added to the polymer solution.
  • acyl halides preferably are chloride derivatives such as adipoyl chloride, sebacoyl chloride, succinyl chloride, and the like.
  • Acyl chloride derivatives of multifunctional carboxylic acids are very unstable in water and will react almost immediately to form the corresponding acid in solution (see, for example, Pine et al., Organic Chemistry, supra, p. 319) and it is this acid, not its halide derivative, that becomes incorporated into the final form of the polymer network as the crosslinkage.
  • one embodiment of the synthesis requires use of anhydrous conditions and anhydrous solvents but without the need for azeotropic distillation (see Examples).
  • the halide derivative is so reactive with water, aqueous leaching of a polymer network with any residual halide derivative will necessarily yield the acid form of the crosslinker in the leachate, not the halide derivative.
  • the leachate is a KATP material.
  • the three-dimensional polymer networks described herein may also be functionalized during synthesis with one or more surfactants, affinity ligands (e.g. monoclonal antibodies), chelators, enzymes, and the like that are immobilized in or on the polymer network.
  • affinity ligands e.g. monoclonal antibodies
  • chelators e.g. monoclonal antibodies
  • enzymes e.g. enzymes, and the like that are immobilized in or on the polymer network.
  • immobilize refers to physical trapping of a functionality within a polymer network as well as chemical bonding of a functionality via covalent, or other bonding, within a polymer network. Methods of immobilizing such functionalities to polymer networks are well known to the practitioner (see, for example, Hoffman et al. U.S. Patent 4,912,032; McCain et al. U.S. Patent 4,737,544; O'Driscoll et al. U.S. Patent 3,859,169, each
  • immobilization of a ligand within KATP polymer gel networks allows the ligand to be exposed to, and/or isolated from, an environment by changing the gel's volume (see discussion on "responsive" gels, below). That is, a substance may be delivered to or removed from an environment by employing a ligand immobilized within a responsive KATP polymer gel of the present invention.
  • the immobilized ligand may be selected for its capability of specifically binding with a substance although the ligand may also bind non- specifically.
  • a ligand e.g. an enzyme or antibody
  • a drug, antibody, or other molecule may be immobilized to, for example, cellulose ether moieties and the gel kept in a dry or shrunken state. When such a gel is swollen, it will incorporate solvent and if the solvent can degrade the labile linkage(s), the drug or antibody or other molecule will be released from the gel into the environment.
  • the material immobilized in the KATP polymer gels described herein may also be a binding component of an affinity binding pair.
  • Suitable binding pairs include an antibody which binds with an antigen or hapten of interest; a receptor that binds with a hormone, vitamin, dye or lipid binding partner in solution; lectins that bind with polysaccharides; DNA or RNA that binds with complementary DNA,RNA, or oligonucleotides; ions that bind with chelators; and the like.
  • a chemically active reactant may be immobilized to provide a means for controlling a reaction.
  • reactions may be cycled on and off as exposure of the immobilized reactant to a reaction condition is regulated by altering the volumetric changes of the gel containing the reactant.
  • Such a system could include an enzyme or antibody immobilized in or on a KATP gel of the present invention to catalyze a reaction with a substrate in a solution of interest (see, for example, Hoffman et al. U.S. Patent 4,912,032, incorporated herein by reference).
  • the functional moieties e.g. affinity ligands
  • the functional moieties also have a known acceptable toxicologicai profile.
  • Additives are defined herein as materials incorporated into a responsive polymer gel network of the invention that have a KATP suitable for the particular use of that gel. Additives include, but are not limited to, stabilizers, biocides, anti-microbials, adhesives.
  • Preferred crosslinked polymer networks of the invention are gels that are "responsive"- i.e. are gels that, when challenged with an environmental change, are affected by that environmental change in that the environmental change causes the entire gel, or a component thereof, to undergo a reversible volumetric change in which the gel expands from a less liquid-filled state or dry state to a more liquid-filled state; or collapses from a more liquid-filled state to a less liquid-filled state.
  • Polymer gels used in the present method may be expanded by either (i) contacting a dried gel with a solvent and allowing the gel to non-reversibly swell with solvent and incorporate any moiety (e.g. a drug, affinity ligand) contained in the solvent; (ii) initiating a reversible volumetric expansion of the gel to incorporate solvent (and any moiety contained therein) by triggering the expansion with a stimulus; or (iii) a combination of (i) and (ii).
  • the term "incorporate” refers to both abso ⁇ tion of a material inside the gel network and adso ⁇ tion of a material on a surface of the gel.
  • the degree of volumetric change between collapsed and expanded states of the preferred "responsive" gels at their particular environmental transition region is quantitatively much greater than the volume change of the gel outside the environmental transition region. Equations describing this volume behavior are not simple monotonic functions (as they are for conventional hydrogels) but contain one particular environmental transition where the volume change is much larger than at other environmental transitions for the same gel.
  • the primary requirement of a responsive polymer gel of the present invention is that the entire gel, or a component, undergo a volume change in response to a change in environmental condition.
  • the gel as a whole may meet these requirements. Nevertheless, the gel may itself include several other (i.e. non-responsive) components as long as at least one component(s) provides the required property.
  • the gel may be a single material such as a single polymer network which meets the volumetric response requirement.
  • the gel may also be a co-polymer, whether a random, alternating, or block co-polymer, that has a KATP and which meets the volumetric response requirement.
  • the gel may also include two or more polymers, each component polymer having a KATP, so long as the result is a physical polymer blend, wherein at least one polymer meets the volumetric response requirement.
  • the gel may also be an interpenetrating polymer network (IPN) in which each KATP polymer maintains its properties.
  • An IPN may possess only a volume change property such as an IPN of HPC and carboxymethy .cellulose.
  • a responsive gel may also be combined in an IPN with a so ⁇ tive-type gel to meet the requirements of vapor extraction, drug delivery, electrophoresis, or other delivery system.
  • a purely responsive polymer may itself be combined in an
  • the IPN with a polymer that has a so ⁇ tive component.
  • the IPN may possess both properties, however, so that at least one polymer member of the IPN provides the so ⁇ tive property and at least another polymer member provides the volume change property. This type of configuration is particularly useful in drug delivery systems.
  • the reversible volume change of the entire gel, or a component thereof, may be either continuous or discontinuous.
  • a "continuous" volume change is marked by a reversible change in volume (i.e. a collapse or swelling) that occurs over a relatively large change in environmental condition.
  • a reversible change in volume i.e. a collapse or swelling
  • Crosslinked gels of the invention may undergo a "discontinuous" volume change in which the reversible transition from swollen to collapsed states, and back again, occurs over an extremely small change in environmental condition, such as less than 0.1 °C or 0.1 pH unit.
  • Such reversible gels are often called
  • phase-transition gels see, for example, Hirotsu et al., J. Chem. Phys. 87:15, 1987, which describes synthetic polymeric gels that undergo phase transitions). There is no stable volume between the swollen and collapsed states at the phase- transition and, in theory, the expansion and/or collapse occurs over an infinitesimally small environmental change.
  • a gel undergoing a continuous pbase- transition may have a similar order of magnitude total volume change as a gel undergoing a discontinuous phase-transition.
  • the preferred responsive gels are sensitive to small changes in a restricted repertoire of environmental "trigger" conditions consisting primarily of temperature, pH, solvent concentration, and ion concentration.
  • environmental "trigger" conditions consisting primarily of temperature, pH, solvent concentration, and ion concentration.
  • any of a variety of environmental changes may be imposed on the gel which allows the specific trigger to induce a volume change.
  • These environmental conditions may be, but are not necessarily, the same as the trigger and include, but are not limited to, a change in temperature, electric field (presence, strength, and/or orientation), magnetic field (presence, strength, an/or orientation), photon energy, pH, solvent composition, ion concentration, concentration of biomolecules, mechanical force, pressure, and the like.
  • the preferred gels of the invention may be combined with a material that acts as a molecular "transducer", converting an environmental condition into an appropriate trigger.
  • a dye may be introduced into a temperature- triggered responsive gel.
  • the dye is designed to trap light of a given wavelength and convert the light energy into heat, thus triggering the gel to undergo a temperature-induced volume change (see, for example, Seasick et al. Nature 346:6282, 1990, incorporated herein by reference).
  • the volumetric changes of gels described herein result from competition between intermolecular forces, usually electrostatic in nature, that act to expand the polymer network; and at least one attractive force that acts to shrink it.
  • volumetric changes in aqueous gels are driven primarily by four fundamental forces: ionic, hydrophobic, hydrogen bonding and van der Waals bonding interactions, either alone or in combination. Each of these interactions may be independently responsible for a volume transition in preferred gels of the invention. Each of these fundamental forces is most strongly affected by a particular trigger. Changes in solvent concentration most strongly affect the van der Waals interaction; changes in temperature most strongly affect hydrophobic interactions and hydrogen bonding; and changes in pH and ion concentration most strongly affect ionic interactions.
  • a gel whose volume change is governed by ionic interactions would include components that are weakly acidic and weakly basic, such as poly(methylmethacrylate)/dimethylaminoethyl methacrylate (see, for example, Siegel et al. Macromolecules 21:3254, 1988) and cellulose ethers such as HPC crosslinked by methods described herein. Gels of this type are sensitive to pH
  • Gels whose volume change is governed by hydrogen bonding will collapse with a decrease in temperature and are exemplified by interpenetrating polymers that comprise acrylamide as one polymer, acrylic acid as the other polymer, and water as the liquid medium. Gels whose volume change is governed by hydrophobic interactions will collapse when challenged with an increase in temperature and are exemplified by N-isopropylacrylamide. Gels whose volume change is governed by van der Waals interactions will behave similarly to those governed by hydrophobic interactions. Gels may be formulated in which the volume change is governed by more than one fundamental force. In particular, gels consisting of copolymers of positively and negatively charged groups meet this requirement.
  • Tc the temperature (Tc) of the phase transition where ( ⁇ ) is the theta temperature of the polymer network in the solvent, and ⁇ 0 is the concentration of the polymer network when in a random walk configuration, using equation 1.
  • T c ⁇ /(l ⁇ 22.5 ⁇ 0 )
  • the value in the denominator is positive for gels that collapse at lower temperature (see Example 4) and negative for gels that collapse at higher temperatures (see Examples 1 and 2).
  • Three osmotic pressures contribute to the total osmotic pressure of a gel, as shown below in equations 2, 3, 4 and 5.
  • V 0 denotes the number of effective crosslinks of the network when it is in the random walk configuration whose density is denoted by ⁇ 0 .
  • This state is referred to as the reference state.
  • the rubber elasticity, x- ubb -- which originates from the configurational entropy of the polymer network, provides a restoring pressure back to the reference polymer network density.
  • x- ubb -- which originates from the configurational entropy of the polymer network, provides a restoring pressure back to the reference polymer network density.
  • x- ubb -- which originates from the configurational entropy of the polymer network, provides a restoring pressure back to the reference polymer network density.
  • x- ubb -- which originates from the configurational entropy of the polymer network, provides a restoring pressure back to the reference polymer network density.
  • x- ubb -- which originates from the configurational entropy of the polymer network, provides a restoring pressure back to the reference polymer network
  • the polymer network tends to shrink, whereas in a good solvent a gel tends to swell.
  • the last factor is the osmotic pressure due to ionization of the polymer network, v ⁇ .
  • the counter-ions within the gel create a gas-type pressure to expand the gel in proportion to the density of counter-ions as well as the absolute temperature, kT, where k is the Boltzmann constant.
  • a general protocol for forming a KATP polymer network of the present invention using a crosslinkable polymer includes the steps of dissolving the KATP polymer(s) in a suitable solvent and allowing the polymer(s) and solvent to mix. A crosslinking agent is then added to the polymer solution, and the solution and crosslinker are further mixed together. The resulting solution may be poured into a solid mold (e.g. between two glass plates), and the crosslinking reaction carried out. In an exemplary sequence, a chemical crosslinking reaction is carried out in the homogenous polymer state at room temperature to form a certain amount of polymer network. Total crosslinking time will vary but is generally less than 24 hours.
  • a polymer network can be made from any KATP polymer with side groups that can react with a di- or multi-functional crosslinking molecule.
  • the polymer solution may also be formed into beads or spheres using crosslinking in a non-solid mold where the reacting solution (polymer, crosslinker and catalyst, if needed) is dispersed in a non-solvent to form a droplet.
  • the solution reacts within the droplet to form a bead.
  • the non-solvent may be considered to be a "mold" for polymer network droplets.
  • U.S. Patent No. 3,208,994 to Rodin et al. generally discloses methods of preparing polysaccharide gel beads using suspension crosslinking.
  • One introduces a water soluble polysaccharide and crosslinker into a suspension medium under agitation to obtain suspended drops of the polysaccharide solution.
  • Another method of preparing gel beads uses inverse emulsion polymerization, in which a monomer solution is introduced into a dispersion solvent to form monomer droplets and polymerization is initiated to form polymer gel beads (see, for example, Hirose et al. Macromolecules 20:1342, 1987, incorporated herein by reference).
  • an aqueous cellulose ether solution, a non-polar saturated hydrocarbon solvent, and a crosslinker are provided and admixed to form a two-phase system.
  • the two-phase system is agitated sufficiently to form droplets of aqueous cellulose ether solution in the two-phase system.
  • the agitation of the two-phase system is maintained to form crosslinked cellulose ether gel beads and the crosslinked cellulose ether gel beads are thereafter recovered from the two-phase system.
  • Polymer networks of the invention also may consist, in whole or in part, of polymers made by copolymerization/crosslinking of monofiinctional and polyfunctional polymerizable monomers.
  • a preferred method for making KATP gels from cellulose ethers involves dissolving a sample of cellulose ether such as HPC or HPMC in an anhydrous solvent that does not contain active hydrogen, such as for example N-methyl pyrolidone (21).
  • the concentration of polymer in the solution may range from about 5-20% by weight of polymer per volume of solution, with a preferred concentration primarily a function of the kind of polymer used in the synthesis.
  • the molecular weight of the cellulose ether should be at least about 20,000. Preferred molecular weights range from about 75,000 to about 150,000. The higher the molecular weight of the polymer, the sharper will be the volume change of the resulting responsive gel. This is because a higher molecular weight will result in formation of a more consistent three-dimensional polymer network.
  • Molecular weights may range up to 1,000,000 or more although it will be understood that viscosity effects will place an upper limit on the molecular weight of the polymer starting material.
  • azeotropic distillation is a preferred method.
  • a first solvent such as DMSO is added to a distillation flask containing the polymer and crosslinker reagents. Both are mixed to achieve a clear solution.
  • a small amount (several hundred ⁇ L) of an acidified solution of first solvent is added, followed by the addition of a second solvent (e.g. toluene).
  • a second solvent e.g. toluene
  • This solution is allowed to react under azeotropic distillation until a gel forms in the flask.
  • the gel is then removed and placed in an excess of deionized water.
  • the water is removed and excess primary alcohol (e.g. methanol) is added to remove excess solvent.
  • the gel is washed and then dried in a desiccator.
  • Synthesis of KATP gels using acyl halide derivatives of dicarboxylic acids generally occurs as follows: While stirring the cellulose ether polymer solution under anhydrous conditions, the solution is cooled slightly below room temperature (in some embodiments to between about 10-20 °C) and a cold solution (in some embodiments between about 2-8 °C) of a preferred acyl halide derivative of a multifunctional carboxylic acid is added as crosslinker to the polymer solution. This solution is stirred and then allowed to sit until gelation has occurred. Gelation time will necessarily vary and may occur within about 2 hours (e.g. for HPC) or as long as 24 hours (e.g. for HPMC). The polymer/crosslinker weight ratio is between about 12/1 and 8/1.
  • a gel which has basic (amine) groups rather than acid groups this may be achieved for example by allowing the acyl halide, cellulose ether reaction product to react with a KATP diamine such as ethylenediamine or hexamethylenedi-unine (21 C.F.R. 175.300 (b) (3) (xxxii) to produce an amine-terminated amide.
  • a KATP diamine such as ethylenediamine or hexamethylenedi-unine (21 C.F.R. 175.300 (b) (3) (xxxii)
  • This opacity signifies that the gel has undergone a volumetric change at a lower critical solution temperature (LCST), and therefore that the gel has temperature responsive characteristics.
  • LCST critical solution temperature
  • the LCST is between 42 and 46 °C.
  • the degree of responsiveness to pH may be assayed using the device and procedures given in Example 1. In the Examples, all the gels were pH responsive, and all gels except those of Examples 3, 6-11 were also temperature responsive.
  • the degree of crosslinking of polymer gels may also be measured by uniaxial compression tests. Briefly, a cylindrical gel disk (approximately 25 mm in diameter) is first swollen to equilibrium in water at 25°C and weight, thickness, and diameter measured using a balance, micrometer, and a ruler, respectively. The gel sample is placed in a water-filled Petri dish and a constant strain applied by adjustment of a micrometer. The relaxation of the applied stress was monitored by computer until the equilibrium, relaxed state was reached. Then the strain is increased in steps and equilibrium value of stress at each point recorded.
  • the equilibrium stress is plotted versus the strain function (a - a 2 ), where a is the ratio of deformed thickness to the unstrained thickness of the sample.
  • This plot is expected to be linear for > 0.90.
  • the shear modulus is obtained from the slope of the initial linear region of the plot using the equations of Mark (see Physical Properties of Polymers Am. Chem. Soc. Wash. D.C., 1984, incorporated herein by reference).
  • the crosslink density of the gel sample is calculated from the equations derived by Harsh et al. (see J. Control Release, 1991, incorporated herein by reference) for non-porous gels, e.g.
  • G RT px ( ⁇ 2f/ ⁇ 2) V3 where: px is the crosslink density; ⁇ 2f is the polymer volume fraction at the network formation; and ⁇ 2 is the polymer volume fraction of the gel during the experiment.
  • Microporous KATP gels are encompassed by the invention.
  • a gas phase is dispersed throughout a fluid polymer phase and the resulting porous material is solidified.
  • the cell or pore size is generally of the order of 100-200 microns or larger (see, for example, Aubert et al. Macromolecule, 21:3468, 1988, incorporated herein by reference).
  • Another method for fabricating microporous gels is to disperse solid particles in a polymer melt or in a polymer solution.
  • the polymer solution or melt is solidified either by chemical crosslinking or by physical means such as freezing. After solidification of the polymer, the solid particles are leached away (see, for example, Mikos et al. Mater. Res. Soc. Symp. Proc. 252:353, 1992, incorporated herein by reference).
  • Microporous gels may also be formed by a process in which co-monomers including crosslinker are polymerized in one phase of a bicontinuous microemulsion, while the other phase forms the cells or pores (see, for example, Hainey et al. Macromolecules 24:117, 1991, incorporated herein by reference). Materials made by this process have a pore size ranging from 1-30 microns. This technique is limited by the ability to find a suitable solvent and non-solvent for the comonomers and emulsifying agent which will form a bicontinuous emulsion.
  • phase inversion refers to the process by which a polymer solution containing one or more polymer precursors, in which the solvent is the continuous phase, inverts into a three- dimensional network or gel where the polymer(s) are now the continuous phase. Phase separation occurs when polymer becomes insoluble in the solvent upon changing the system conditions (see, for example, Resting Synthetic Polymeric Membranes: A Structural Perspective, J. Wiley and Sons, NY, 1985, incorporated herein by reference).
  • one method of the invention includes contacting a dissolved polymer with another solvent that effectively removes the solvent from the polymer and precipitates the polymer out of solution, forming a microporous interconnected structure that is crosslinked to convert it into a responsive gel.
  • a preferred method described herein for making microporous volume change gels can be applied to make crosslinked microporous gels from any crosslinkable polymer-solvent system which phase separates with changes in temperature.
  • Many aqueous-soluble polymers phase separate with changes in temperature.
  • Even aqueous polymer solutions which don't phase separate at a particular temperature can be forced to phase separate at another temperature by adding, for example, an organic solvent such as ethanol or a suitable salt, such as, for example, 1 M NaCl.
  • Microporous gels may be "fast response" gels.
  • fast response means that the gel reaches 90% of its maximum volumetric swelling or 90% of its minimum volumetric collapse in a time that is at least ten times faster than a comparable non-porous gel of the same geometry when both gels are subjected to a similar change in an environmental condition.
  • Gref et al. (Science 263:1600, 1994) have developed biodegradable nanospheres using amphiphilic polymers that phase-separated during emulsification. Up to 45 percent by weight of drug loading was achieved by dissolving the drug in the same organic solvent that dissolved the copolymer. Although drug loading is high using this method, the drug must be dissolved in an organic solvent.
  • a protein is made to partition selectively into one of two immiscible aqueous polymer solution phases which are in contact with each other.
  • high loadings of biologically active compounds into gels may be obtained with solution controlled gel so ⁇ tion using a second, loading polymer phase.
  • the second loading polymer and salt have a synergistic effect which causes partitioning and so ⁇ tion (exceeding 20 % by weight) of the compound into the polymer gel.
  • the second loading polymer need not be a gel but is most preferably soluble in the same solvent that is the gel's solvent.
  • Solution-controlled gel so ⁇ tion is utilized in the Examples presented herein for loading a solute into a crosslinked gel.
  • the partitioning behavior is governed by properties such as molecular weight of the polymers, the type and concentration of salts and the relative hydrophobicity/hydrophilicity of the solute. Differences in the various interaction energies between the solute and the different polymers leads to a partition coefficient (concentration of solute in the gel/concentration of the solute in the second loading polymer) greater than one (i.e. preferential loading by the gel) or less than one (i.e. preferential loading by the second loading polymer).
  • Crosslinked gels are pre-equilibrated with solute-free, loading polymer solutions.
  • the equilibrated gels are then separated from the loading polymer solution.
  • a solution with the same loading polymer concentration as the pre- swelling solution but including a solute and a salt is added.
  • the tube is then agitated to mix gel and salt/solute solution. Equilibrium is reached in less than 15 minutes
  • the solute concentration in the second, loading polymer phase may be determined by a variety of methods, depending upon the solute of interest. For spectrophotometric assays, light absorbance is measured at 280 nm for proteins; at 630 nm for blue dextran; and at 520 nm for Vitamin B12 with a UV/VIS spectrophotometer. The concentration of solute in the gel phase is determined by a mass balance. Cellulose ethers are advantageous for loading by this method. Because the degree of substitution of the anhydroglucose unit has a great effect on the degree of hydrophilicity, cellulose ethers differ in their hydrophilic nature.
  • phase systems formed by these polymers including cellulose ethers, can be expected to be selective in separating substances which themselves are mainly water; that is substances that fa within the same part of the solvent spectrum. Examples are particles and macromolecules of biological origin.
  • Aqueous solutions of the following polymers ar mutually immiscible and are ranked in order of increasing hydrophobicity: dextran sulfate, carboxymethyl dextran, dextran, hydroxypropyldextran, methylcellulose, hydroxypropylcellulose, polyvinylalcohol, polyethylene glycol and polypropylene glycol.
  • Solute is recovered from the loaded polymer as follows: Solute is chosen to have a very low partition coefficient in pure buffer, lacking any polymer. The solute contained in the loaded gel after the partitioning experiment is recovered by adding pure buffer lacking any to the loaded gel. The gel is separated by centrifugation fro any supernatant and the concentration of the solute in the supernatant measured using a spectrophotometer. This procedure is repeated until the solute concentration in the supernatant is negligible.
  • solute recovery can be accomplished by causing the gel to undergo to volumetric collapse using established methods (see, for example, Cussler U.S. Patent 4,555,344, incorporated herein by reference).
  • the biologically active compounds that may be loaded into the polymer networks of the present invention are any substance having biological activity, including proteins, polypeptides, polynucleotides, nucleoproteins, polysaccharides, glycoproteins, lipoproteins, and synthetic and biologically engineered analogs thereof.
  • biologically active compounds that might be utilized in a delivery application of the invention include literally any hydrophilic or hydrophobic biologically active compound.
  • the drug is one that has already been deemed safe and effective for use by the appropriate governmental agency or body.
  • drugs for human use listed by the FDA under 21 C.F.R. 330.5, 331 through 361; 440-460; drugs for veterinary use listed by the FDA under 21 C.F.R. 500-582, incorporated herein by reference are all considered acceptable for use in the present novel polymer networks.
  • Drugs that are not themselves liquid at body temperature can be inco ⁇ orated into polymers, particularly gels.
  • peptides and proteins which may normally be lysed by tissue-activated enzymes such as peptidases, can be passively protected in gels as well.
  • biologically active compound includes pharmacologically active substances that produce a local or systemic effect in animals, plants, or viruses.
  • the term thus means any substance intended for use in the diagnosis, cure, mitigation, treatment or prevention of disease or in the enhancement of desirable physical or mental development and conditions in an animal, plant, or virus.
  • animal used herein is taken to mean mammals, such as primates, including humans, sheep, horses, cattle, pigs, dogs, cats, rats, mice; birds; reptiles; fish; insects; arachnids; protists (e.g. protozoa); and prokaryotic bacteria.
  • plant means higher plants (angiosperms, gymnosperms), fungi, and prokaryotic blue-green "algae” ( i.e. cyanobacteria).
  • the biologically active compound may be any substance having biological activity, including proteins, polypeptides, polynucleotides, nucleoproteins, polysaccharides, glycoproteins, lipoproteins, and synthetic and biologically engineered analogs thereof.
  • protein is art-recognized and for purposes of this invention also encompasses peptides.
  • the proteins or peptides may be any biologically active protein or peptide, naturally occurring or synthetic.
  • proteins include antibodies, enzymes, steroids, growth hormone and growth hormone-releasing hormone, gonadotropin-releasing hormone, and its agonist and antagonist analogues, somatostatin and its analogues, gonadotropins such as luteinizing hormone and follicle-stimulating hormone, peptide-T, thyrocalcitonin, parathyroid hormone, glucagon, vasopressin, oxytocin, angiotensin I and ⁇ , bradykinin, kallidin, adrenocorticotropic hormone, thyroid stimulating hormone, insulin, glucagon and the numerous analogues and congeners of the foregoing molecules.
  • gonadotropins such as luteinizing hormone and follicle-stimulating hormone, peptide-T, thyrocalcitonin, parathyroid hormone, glucagon, vasopressin, oxytocin, angiotensin I and ⁇ , bradykinin, kallidin,
  • Classes of biologically active compounds which can be loaded into crosslinked gels using the methods of this invention include, but are not limited to, anti-AIDS substances, anti-cancer substances, antibiotics, immunosuppressants (e.g. cyclosporine) anti-viral substances, enzyme inhibitors, neurotoxins, opioids, hypnotics, antihistamines, lubricants tranquilizers, anti-con vulsants, muscle relaxants and anti-Parkinson substances, anti-spasmodics and muscle contractants, miotics and anti-cholinergics, anti-glaucoma compounds, anti-parasite and/or anti-protozoal compounds, anti-hypertensives, analgesics, anti-pyretics and anti-inflammatory agents such as NSAIDs, local anesthetics, ophthalmics, prostaglandins, anti-depressants, anti-psychotic substances, anti-emetics, imaging agents, specific targeting agents, neurotransmitters, proteins, cell response modifiers, and vaccines.
  • Anti-ATDS substances are substances used to treat or prevent Autoimmune Deficiency
  • AIDS AIDS
  • examples of such substances include CD4, 3'-azido-3'-deoxythymidine (AZT), 9-(2-hydroxyethoxymethyl)-guanine acyclovirO, phosphonoformic acid, 1-adamantanamine, peptide T, and 2', 3' dideoxycytidine.
  • Anti-cancer substances are substances used to treat or prevent cancer. Examples of such substances include methotrexate, cisplatin, prednisone, hydroxyprogesterone, medroxyprogesterone acetate, megestrol acetate, diethylstilbestrol, testosterone propionate, fluoxymesterone, vinblastine, vincristine, vindesine, daunorubicin, doxorubicin, hydroxyurea, procarbazine, ammoglutethimide, mechlorethamine, cyclophosphamide, melphalan, uracil mustard, chlorambucil, busulfan, carmustine, lomusline, dacarbazine (D ⁇ C: dimemyltria-»nomida-- ⁇ lecarboxamide), methotrexate, fluorouracil, 5-fluorouracil, cytarabine, cytosine arabinoxide, mercaptopurine, 6-mercaptopurine,
  • Antibiotics are art recognized and are substances which inhibit the growth of or kill microorganisms. Antibiotics can be produced synthetically or by microorganisms.
  • antibiotics examples include penicillin, tetracycline, chloramphenicol, minocycline, doxycycline, vanomycin, bacitracin, kanamycin, neomycin, gentamycin, erythromicin and cephalosporins.
  • Anti-viral agents are substances capable of destroying or suppressing the replication of viruses.
  • anti-viral agents include a-methyl-P-adamantane methylamine, l,-D-ribofuranosyl-l,2,4-triazole-3 caiboxamide, 9-[2-hyo xy-ethoxy]methylguanine, adamantanamine, 5-iodo-2'-deoxyuridine, trifluorothymidine, interferon, and adenine arabinoside.
  • Enzyme inhibitors are substances which inhibit an enzymatic reaction.
  • enzyme inhibitors include edrophonium chloride, N-methylphysostigmine, neostigmine bromide, physostigmine sulfate, tacrine HCL, tacrine.l-hydroxy maleate, iodotubercidin, p-bromotetramisole, l ⁇ -(alpha-diethylaminopropionyl)- phenothiazine hydrochloride, calmidazolium chloride, hemicholinium-3, 3,5-dinitrocatechol, diacylglycerol kinase inhibitor I, diacylglycerol kinase inhibitor ⁇ , 3-phenylpropargylamine, acetate, carbidopa, 3-hydroxybenzylhydrazine HCl, hydralazine HCl, clorgyline HCl, deprenyl HC1,L(-)-,
  • Neurotoxins are substances which have a toxic effect on the nervous system, e.g. nerve cells.
  • Neurotoxins include adrenergic neurotoxins, cholinergic neurotoxins, dopaminergic neurotoxins, and other neurotoxins.
  • Examples of adrenergic neurotoxins include N-(2-cUoroethyl)-N-ethyl-2-bromobenzylamine hydrochloride.
  • cholinergic neurotoxins examples include acetylethylcholine mustard hydrochloride.
  • dopaminergic neurotoxins include 6-hydroxydop-tmine HBr, l-methyl-4-(2-methylphenyl)-l, 2,3,6- tetrahydro-pyridine hydrochloride, l-methyl-4-phenyl-2,3- dihydropyridinium perchlorate, N-methyl-4-pheny 1-1, 2,5,6- tetrahydropyridine HCl, l-methyl-4-phenylpyridinium iodide.
  • Opioids are substances having opiate like effects that are not derived from opium.
  • Opioids include opioid agonists and opioid antagonists.
  • Opioid agonists include codeine sulfate, fentanyl citrate, hydrocodone bitartrate, loperamide HCl, mo ⁇ hine sulfate, noscapine, norcodeine, normo ⁇ hine, thebaine.
  • Opioid antagonists include nor-bm- ⁇ to ⁇ himine HCl, bupreno ⁇ hine, chlornaltrexamine 2HC1, funaltrexamione
  • HCl nalbuphine HCl, nalo ⁇ hine HCl, naloxone HCl, naloxonazine, naltrexone HCl, and naltrindole HCl.
  • Hypnotics are substances which produce a hypnotic effect.
  • Hypnotics include pentobarbital sodium, phenobarbital, secobarbital, thiopental and mixtures, thereof, heterocyclic hypnotics, dioxopiperidines, glutarimides, diethyl isovaleramide, a-bromoisovaleryl urea, urethanes and disulfanes.
  • Antihistamines are substances which competitively inhibit the effects of histamines.
  • Examples include pyrilamine, chlo ⁇ heniramine, tetrahydrazoline, and the like.
  • Lubricants are substances that increase the lubricity of the environment into which they are delivered.
  • biologically active lubricants include water and saline.
  • Tranqiiilizers are substances which provide a tranquilizing effect.
  • tranquilizers include chloropromazine, promazine, fluphenzaine, res ⁇ ine, dese ⁇ idine, and meprobamate.
  • Anti-convulsants are substances which have an effect of preventing, reducing, or eliminating convulsions.
  • examples of such agents include primidone, phenytoin, valproate, Chk and ethosuximide.
  • Muscle relaxants and anti-Parkinson agents are agents which relax muscles or reduce or eliminate symptoms associated with Parkinson's disease.
  • Examples of such agents include mephenesin, methocarbomal, cyclobenzaprine hydrochloride, trihexylphenidyl hydrochloride, levodopa/carbidopa, and biperiden.
  • Anti-spasmodics and muscle contractants are substances capable of preventing or relieving muscle spasms or contractions.
  • examples of such agents include atropine, scopolamine, oxyphenonium, and papaverine.
  • Miotics and anti-cholinergics are compounds which cause bronchodilation. Examples include echothiophate, piloca ⁇ ine, physostigmine salicylate, diisopropylfluorophosphate, epinephrine, neostigmine, carbachol, methacholine, betbanechol, and the like.
  • Anti-glaucoma compounds include betaxalol, piloca ⁇ ine, timolol, timolol salts, and combinations of timolol, and/or its salts, with piloca ⁇ ine.
  • Anti-parasitic, -protozoa! and -fungals include ivermectin, pyrimethamine, trisutfapyrimidine, clindamycin, amphotericin B, nystatin, flucytosine, natamycin, and miconazole.
  • Anti-hypertensives are substances capable of counteracting high blood pressure. Examples of such substances include alpha-methyldopa and the pivaloyloxyethyl ester of alpha-methyldopa.
  • Analgesics are substances capable of preventing, reducing, or relieving pain.
  • analgesics examples include mo ⁇ hine sulfate, codeine sulfate, meperidine, and nalo ⁇ hine.
  • Anti-pyretics are substances capable of relieving or reducing fever and anti-inflammatory agents are substances capable of counteracting or suppressing inflammation.
  • anti-inflammatory agents include aspirin (salicylic acid), indomethacin, sodium indomethacin trihydrate, salicylamide, naproxen, colchicine, fenoprofen, sulindac, diflunisal, diclofenac, indoprofen and sodium salicylamide.
  • Local anesthetics are substances which have an anesthetic effect in a localized region.
  • Examples of such anesthetics include procaine, lidocain, tetracaine and dibucaine.
  • Ophthalmics include diagnostic agents such as sodium fluorescein, rose bengal, methacholine, adrenaline, cocaine, and atropine.
  • Ophthalmic surgical additives include alpha-chymotrypsin and hyaluronidase.
  • Pmstaglandins are art recognized and are a class of naturally occurring chemically related, long-chain hydroxy fatty acids that have a variety of biological effects.
  • Anti-depressants are substances capable of preventing or relieving depression.
  • anti-depressants examples include imipramine, amitriptyline, nortriptyline, protriptyline, desipramine, amoxapine, doxepin, maprotiline, tranylcypromine, phenelzine, and isocarboxazide.
  • Anti-psychotic substances are substances which modify psychotic behavior. Examples of such agents include phenothiazines, butyrophenones and thioxanthenes. /02276 PC17US95/09815
  • Anti-emetics are substances which prevent or alleviate nausea or vomiting.
  • An example of such a substance includes dramamine.
  • Imaging agents are agents capable of imaging a desired site, e.g. tumor, in vivo.
  • imaging agents include substances having a label which is detectable in vivo, e.g. antibodies attached to fluorescent labels.
  • the term antibody includes whole antibodies or fragments thereof.
  • Specific targeting agents include agents capable of delivering a therapeutic agent to a desired site, e.g. tumor, and providing a therapeutic effect.
  • Examples of targeting agents include agents which can carry toxins or other agents which provide beneficial effects.
  • the targeting agent can be an antibody linked to a toxin, e.g. ricin A or an antibody linked to a drug.
  • Neurotransmitters are substances which are released from a neuron on excitation and travel to either inhibit or excite a target cell.
  • Examples of neurotransmitters include dopamine, serotonin, q-aminobutyric acid, norepinephrine, histamine, acetylcholine, and epinephrine.
  • Cell response modifiers are chemotactic factors such as platelet-derived growth factor
  • PDGF vascular endothelial growth factor
  • Other chemotactic factors include neutrophil-activating protein, monocyte chemoattractant protein, macrophage-inflammatory protein, platelet factor, platelet basic protein, and melanoma growth stimulating activity; epidermal growth factor, transforming growth factor (alpha), fibroblast growth factor, platelet-derived endothelial cell growth factor, insulin-like growth factor, nerve growth factor, and bone growth/cartilage-inducing factor (alpha and beta), or other bone mo ⁇ hogenetic protein.
  • cell response modifiers are the interleukins, interleukin inhibitors or interleukin receptors, including interleukin 1 through interleukin 10; interferons, including alpha, beta and gamma; hematopoietic factors, including erythropoietin, granulocyte colony stimulating factor, macrophage colony stimulating factor and granulocyte-macrophage colony stimulating factor; tumor necrosis factors, including alpha and beta; transforming growth factors (beta), including beta-1, beta-2, beta-3, inhibin, and activin; and bone mo ⁇ hogenetic proteins.
  • interleukins interleukin inhibitors or interleukin receptors, including interleukin 1 through interleukin 10
  • interferons including alpha, beta and gamma
  • hematopoietic factors including erythropoietin, granulocyte colony stimulating factor, macrophage colony stimulating factor and granulocyte-macrophage colony stimulating factor
  • Polymer networks of the present invention have a wide variety of uses.
  • a number of applications for the responsive gels of the invention are listed in Gel Science, Inc. brochures "Gel Sciences, the leader in Engineered Response Gels", G001-2/94-10M; “Separations”, S001-2/94-10M, and “Controlled Release", CR001- 2/94-lOM, which are incorporated herein by reference. These applications include: 1)
  • responsive gels of the present invention may be used to selectively incorporate a solvent from a solute or separate a protein (or a drug or other solute) from a solution.
  • the polymer networks of the invention are thus generally applicable to any process of selectively excluding a solute from a solvent by selectively incorporating the solvent.
  • selectively incoiporating refers to procedures whereby all, or a portion, of a low molecular weight solvent (e.g. water) is selectively removed by a polymer network from a solution of a higher molecular weight solute (e.g. synthetic or natural polymers, organic compounds, proteins, suspended particles and the like).
  • high molecular weight solute refers to solutes having a molecular weight of at least about 250.
  • Solvent/solute systems that may be utilized in the present invention include systems in which solute is dissolved and those in which solute is dispersed or suspended in solution.
  • the polymer gel network does not necessarily incorporate the solute if the solute is large enough.
  • the fluid remaining after so ⁇ tion is concentrated with solute and may be removed.
  • a preferred separations process functions by first contacting a solvent and solute with a polymer gel network of the invention capable of selective incorporation of the solvent. The gel physically expands as the entire gel, or a so ⁇ tive component thereof, accumulates solvent within the interior of the gel.
  • At least part of the solvent is thereby incorporated by the gel, but solute is excluded from entering the gel.
  • the concentrated solute external to the swollen gel is separated from the swollen gel by centrifugation, filtration, or other conventional methods.
  • the expanded gel may be discarded.
  • the gel may also be collapsed such that solvent is released. This "regeneration" step is preferred so that the solvent-incorporating polymer gel is returned to a condition where it is again available to selectively accumulate solvent (see, for example, Cussler U.S. Patent 4,555,344, incorporated herein by reference).
  • Polymer gels used in this method may be expanded by either (i) contacting a gel with a solvent containing a solute and allowing the gel to non-reversibly swell and selectively incorporate the solvent; (ii) initiating a reversible volumetric expansion of the gel to selectively incorporate solvent by triggering the expansion with a stimulus; or (iii) a combination of (i) and (ii). Expansion is particularly advantageous and energy efficient for initiating selective incorporation when a convenient environmental trigger is available. Solvent incorporated by polymer gels can preferably be disgorged by initiating a volumetric gel collapse. In preferred embodiments of the invention, therefore, a solvent-containing polymer gel of the invention is challenged with an environmental change (e.g.
  • Example 1 pH; see Example 1
  • the environmental change affects the gel by causing the entire gel, or a component thereof, to undergo a collapse.
  • the collapsed polymer gel can then be separated from the disgorged solvent by, for example, filtration and/or centrifugation. Reversible collapse of the polymer gels is particularly useful for regenerating the gel because, after the polymer gel is collapsed, it may be re-expanded. The solvent released during this regeneration may be recycled from the system or discharged as waste solvent.
  • responsive gels of the present invention may be used to selectively incorporate a solute from a solvent to separate a protein (or a drug or other solute) from a solution.
  • the polymer networks of the invention are thus generally applicable to any process of selectively excluding a solute from a solvent by selectively incorporating the solute.
  • a preferred separations process functions by first contacting a solvent and solute with a polymer gel netwoik of the invention capable of selective incorporation of the solute.
  • the gel will contain an immobilized ligand that will form a binding pair with the solute of choice.
  • the gel physically expands as the entire gel, or a so ⁇ tive component thereof, accumulates and binds solute within the interior of the gel. At least part of the solute is thereby incorporated by the gel.
  • the concentrated solvent external to the swollen gel is separated from the swollen gel by centrifugation, filtration, or other conventional methods.
  • ligands that scavenge lipids are attached to KATP gels of the invention and are used to reduce the level of undesirable lipids present in the gastrointestinal tract of an animal.
  • KATP cellulose ethers containing multiple reactive hydroxyl groups are particularly suitable for this purpose since the ligands may be bound thereto via stable ether linkages.
  • Ligands for scavenging lipids are generally hydrophobic, capable of being attached to the polymer gel and may range from 1 to about 50% of ligand groups relative to the polymer. They are exemplified by straight chain aliphatics between C, 2 and C u , as well as cholesterol itself.
  • Hydroxyl groups of ligands may be converted to epoxy groups for reaction with KATP cellulose ether polymers of the invention.
  • lipids which can be removed include cholesterol, cholesterol esters, steroids, fat soluble drugs, fatty acids and fatty acid esters (see, for example, Nightingale et al. Future Perspectives of Biomedical Polymers, Dec. 4-6, 1992, Maui, HI).
  • immobilization and protection of a catalyst such as an enzyme within a responsive KATP gel enables the immobilized enzyme to be active and effective in environmental conditions in which the gel is expanded (see Example 1).
  • Changing the environment e.g. lowering pH
  • the polymer gel networks of the present invention can be used to deliver a compound (e.g. a drug) into an environment.
  • a compound e.g. a drug
  • Drug delivery from acrylate-based hydrogels has been described by Kou et al.
  • a KATP responsive gel is loaded with a biologically active compound at one temperature and induced to undergo a volumetric collapse to disgorge the entrained biologically active compound at another temperature. Delivery of the compound may be modulated by a temperature higher than the temperature of the gel in its loading mode (see, for example, Gutowska et al. J. Control Release 22:95, 1992: using NIPA to release heparin at high temperature).
  • a microporous KATP responsive gel is loaded with a biologically active compound at one temperature and induced to undergo a volumetric expansion at another temperature to allow fluid from the environment of use (e.g. blood, lymph) to enter the expanded gel and biologically active compound to exit the expanded gel via diffusion through the pores.
  • the gel expands to release a drug during exposure to pH conditions that are different than the pH conditions to which it is exposed in the loading mode.
  • Polymer gel networks of the present invention can be prepared in any of a variety of different drug-delivery formulations, depending on the mode by which the compound is to be delivered.
  • the different formulations include, but are not limited to, those suitiable for oral delivery, mucosal delivery, nasal delivery, ocular delivery, vaginal delivery, rectal delivery, dermal delivery (e.g. transdermal delivery), and internal delivery.
  • Formulations can be prepared that are suitable for delivery to humans, animals (including mammals, birds, reptiles, fish, insects, and arachnids), or plants. Particular examples of such different formulations are discussed individually below. The descriptions presented below are not intended to be limiting of the present invention, but rather are intended to exemplify the advantages of the safe polymer gel networks of the present invention for use in delivering compounds to an environment.
  • Polymer gel compositions of the present invention are particularly useful for oral delivery compositions.
  • polymer gel networks of the present invention that are responsive to changes in pH can be utilized to effect controlled release of compounds at specific locations along the gastro-intestinal tract.
  • polymer gel networks that are responsive to changes in pH can be utilized, for example, to effect controlled release of substances into only one of a cow's stomachs.
  • a cellulose ether gel such as HPC with an LCST near body temperature (e.g. 42° C) should have its LCST shifted to a lower temperature at lower pH.
  • a responsive gel may be made from starting materials (i.e. cellulose ethers of various configurations) that vary in their hydrophobic/hydrophilic nature when ionized, so that the methods described herein may be used to make a reversibly responsive, pH-sensitive gel with an LCST designed to match the body temperature of a desired subject.
  • the LCST of preferred cellulose ethers is well known and can be easily determined and verified.
  • Exemplary LCST's are 49° (MEC); 42°-46° (HPC); 59° (methyl(hydroxypropyl)cellulose: HPMC); 60° methyl(hydroxyethyl)cellulose; and 55°-70° (ethyl(hydroxyethyl)cellulose).
  • Polymer gel compositions that are responsive to changes in other environmental parameters can also be utilized in controlled release oral delivery formulations of the present invention.
  • polymer gel networks that are responsive to a magnetic or electric field can be used to specifically release a compound at a desired location or time.
  • One particular application for such a composition of the present invention is in the delivery of fertility drugs (e.g. hormones) to fish.
  • the present invention offers oral delivery compositions composed of responsive gel networks that, for example, collapse in response to the introduction of a magnetic field (see, for example, USSN 08/393,971, filed February 24, 1995, incorporated herein by reference). Fish fertility hormones can be incorporated into such compositions, which can then be administered to fish. Once all fish have had a chance to ingest the compositions, release of the incorporated hormone can be coordinately induces by application of a magnetic field.
  • formulations that are useful for delivery of biologically active compounds to humans or animals are known in the art such as, for example, tablets, capsules, lozenges, pumps, etc., including osmotically controlled systems (see, for example, Theeuwes Drug Absorption Prescott et al. (eds) ADIS Press, 157, 1987; Eckenhoff et al. U.S. Patent No. 4,539,004; Eckenhoff et al. U.S. Patent No. 4,474,575).
  • the present invention provides improved versions of each of these oral delivery formulations, because utilization of responsive gel polymers allows controlled substance release, and also offers protection of substance activity until the point of release.
  • a coated tablet in which a biologically active compound is incorporated within a tablet that is substantially coated with a responsive polymer gel network of the present invention.
  • a coated tablet of the present invention provides for protection of the biologically active compound until the point of release, and for release of the biologically active compound in response to a predetermined change in environmental condition (e.g. pH, magnetic field, electric field, electromagnetic radiation, etc.).
  • a predetermined change in environmental condition e.g. pH, magnetic field, electric field, electromagnetic radiation, etc.
  • Present-day controlled release coated tablets rely on differing solubilities of coating components to regulate release of encapsulated materials.
  • controlled-release tablets are available that are coated with a membrane that is punctuated with soluble components (see, for example, Healey "Enteric Coatings and Delayed Release” in Drug Delivery to the Gastro-Intestinal Tract Hardy et al. (eds) Ellis Horwood, Inc., Ch. 7, 1989).
  • the soluble components dissolve and the tabletted material is release through the resultant pores in the membrane.
  • One disadvantage with this system is that, although release of the tabletted material is delayed, it is not really “controlled” in the sense that it cannot be predicted at exactly what point the soluble plugs will have dissolved.
  • Coated tablets of the present invention offer improved controlled release properties.
  • Another preferred oral delivery formulation of the present invention utilizes responsive polymer gel networks in pump-type delivery systems that are somewhat analogous to present-day osmotically-controlled oral delivery systems.
  • Present-day osmotically-controlled oral delivery systems include the OROS * and OSMET * systems from Alza Corporation (Palo Alto, CA; see, for example, Eckenhoff et al. U.S.
  • Figure 3 presents various embodiments of present-day osmotically-controlled oral delivery systems.
  • one side of the osmotic delivery device housing 100 is comprised of a semi-permeable membrane
  • the side opposite the semi-permeable membrane 110 has a delivery orifice 120.
  • a moveable partition 130 positioned inside the housing separates a drug compartment 140 from an osmotic agent compartment 150.
  • the osmotic agent expands and pushes the moveable partition 130 toward the delivery orifice 110 so that drug located in the drug compartment 140 is pushed out through the delivery orifice 110 and into the subject.
  • the present invention provides a somewhat analogous system, in which the osomotic agent is replaced by a crosslinked polymer gel network having a suitable KATP.
  • the polymer gel netwoik is a responsive polymer gel network, and drug is delivered not by osmotic action, but as a result of the responsive polymer gel network expanding in response to a change in environmental condition.
  • the polymer gel network expands in response to a change in pH, and the drug is not delivered until the device passes through the portion of the gastrointestinal tract in which the appropriate pH is achieved.
  • the polymer gel network comprises a crosslinked polysaccharide gel network (e.g. a cellulosic gel network such as those described in Examples 1-11). This type of oral delivery system of the present invention is particularly useful for delivery of insoluble agents such as, for example, carbamazepine, phenytoin, griseofulvin, cyclosporine, etc.).
  • FIG. 3B Another embodiment of a present-day osmotically-controlled oral delivery system is presented in Figure 3B.
  • the housing 100 is comprised of a rigid, semi- permeable membrane.
  • the osmotic agent forms a layer 160 inside the housing and surrounding the drug compartment 140.
  • a flexible, impermeable reservoir wall 170 lines the drug compartment 140, and separates it from the osmotic agent.
  • a delivery tube 180 is positioned inside the drug compartment so that it provides a passageway to the external environment, by means of the delivery orifice 110.
  • the present invention provides a device that is somewhat analogous to the device depicted in Figure 3B, differing in that the osomotic agent depicted in Figure 3B is replaced by a crosslinked polymer gel network having a suitable KATP.
  • Figure 3C Yet another embodiment of a present-day osmotically-controlled oral delivery system is presented in Figure 3C.
  • the housing 100 is comprised of a semi-permeable membrane that defines a single compartment 145 with a delivery orifice 110.
  • Both the osmotic agent and the rdug are disposed within the compartment 145.
  • gastro ⁇ intestinal juices permeate the compartment 145, so that the osmotic agent is caused to swell.
  • the increase in osmotic pressure results in expulsion of the drug through the delivery orifice 110.
  • the improvement of the provided by the present invention is the use of a safe polymer gel network instead of an osmotic agent.
  • a safe, environmentally responsive, gel network is utilized.
  • the polymer gel network comprises a crosslinked polysaccharide gel network (e.g. a cellulosic gel network such as those described in Examples 1-11).
  • Mucosal Delivery Formulations Preferred mucosal delivery systems of the present invention are bioadhesive systems utilizing safe polymer gel networks of the present invention.
  • bioadhesive refers to the property, displayed by certain compounds, of showing an affinity for biological tissue.
  • Example 19 describes preferred bioadhesive polymer gel networks of the present invention, that can effectively be utilized in mucosal delivery fomrulations to effect controlled drug delivery to mucosal tissues.
  • Ocular Delivery Formulations Many different kinds of ocular preparations incorporating gels, or gelling materials, are known in the art (see, for example, Davis et al. U.S. Patent No. 5,192,535; Missel et al. U.S. Patent No. 5,212,162; Joshi et al. U.S. Patent No. 5,252,318; Viegas et al. U.S. Patent No. 5,300,295; Haslam et al. U.S. Patent No.
  • the present invention provides improved gel compositions for ocular delivery applications.
  • the present invention provides sustained delivery gel compositions in which release of a drug incorporated into the gel matrix occurs over a relatively long period of time (see, for example, Example 12).
  • the present invention also provides ocular delivery formulations comprising responsive gel compositions, so that delivery of a desired substance can be initiated in response to a change in environmental condition.
  • Safe polymer gel networks loaded with a desired biologically active compound can be incorporated into contact lenses, or other ophthalmic compositions according to methods known in the art, and can subsequntly be brought into contact with the eye of a subject, so that the desired biologically active compound is released in a sustained manner and or in response to a particular change in environmental condition.
  • a desired biologically active compound e.g. an ophthalmic diagnostic agent or surgical additive, an anti-glaucomal, anti-viral, or anti-microbial compound, a lubricant, etc.
  • a lightly- crosslinked safe polymer gel of the present invention is utilized as a lacrimator.
  • Such a composition has advantages over eye drops that are currently used as lacrimators because, by virtue of being lightly crosslinked, it is more viscous than an eyedrop and is not immediately cleared from the eye.
  • Particularly preferred compositions are bioadhesive (see, for example, Example 19).
  • Safe polymer gel compositions of the present invention can be utilized for vaginal delivery of biologically active compounds.
  • vaginal delivery formulation of the present invention a pH- responsive polymer gel network loaded with an anti-fungal compounded is prepared and utilized for treatment of yeast infections. Infection of the vaginal tract with yeast results in alkalinization of the environment.
  • a responsive polymer gel network can be prepared according to the principles and procedures described herein to release an antifungal compound in response to the increase in pH. As the infection is brought under control, the pH is decreased, and the responsive polymer gel network ceases to deliver more drug.
  • the present invention provides controlled release compositions that are engineered so that drug is delivered only when it is needed, i.e. when the pH is elevated.
  • Another embodiment of a vaginal delivery formulation of the present invention utilizes a safe polymer gel network to deliver water to a dehydrated vagina.
  • Safe polymer gel networks of the present invention can be utilized to deliver water to a dry vaginal, either by, for example, simple deso ⁇ tion, or, in the case of compositions utilizing responsive gel networks, in response to a predetermined change in an environmental condition.
  • a vaginal delivery formulation of the present invention comprises a safe polymer gel network loaded with a spermicide (and/or a viricide).
  • Such a contraceptive vaginal delivery formulation can offer advantages over present-day contraceptive devices, because they can be engineered, according to the principles and procedures set forth herein, to release the spermicide and/or viricide in response to a particular, predetermined, change in environmental condition.
  • vaginal delivery formulation of the present invention comprises a safe polymer gel network loaded with a vaccine, for example to protect against a sexually transmitted disease (e.g. a herpes virus or an immunodeficiency virus; see, for example, Mark et al. Science 260: 1323, 1993, incorporated herein by reference).
  • a sexually transmitted disease e.g. a herpes virus or an immunodeficiency virus; see, for example, Mark et al. Science 260: 1323, 1993, incorporated herein by reference.
  • Safe polymer gel networks of the present invention can readily be prepared in suppository formulations to allow delivery of biologically active compounds through the rectum. Rectal delivery allows increased bioavailability of delivered compounds
  • Dermal Delivery Formulations Polymer gels of the present invention incorporating, for example, a medicament like hyaluronic acid, may be incorporated into a bandage, gauze or other conventional wound dressing, to allow dermal delivery of the medicament.
  • responsive gels can be incorporated into a dermal delivery formulation, so that, upon activation by an appropriate environmental trigger such as a temperature change or a change in the energy of incident light, the responsive gel collapses and disgorges the entrained medicament to the wound environment. If the gel is triggered to expand and release the medicament, it may also incorporate wound exudates during the expansion (see, for example, U. S. Patent 4,659,700, incorporated herein by reference).
  • Polymer gel compositions can also be incorporated into transdermal devices, and, in preferred embodiments, can be formulated into a novel, bi-layer transdermal device.
  • Present-day transdermal devices are tri-layer devices, comprising a backing, a reservior (comprising the drug to be delivered in some sort of matrix), and a membrane.
  • the membrane provides the rate-limiting step in drug delivery, and also typically has bioadhesive characteristics so that the transdermal device has an affinity for skin.
  • THe transdermal device is positioned on skin so that the membrane is in contact with the skin, and the drug is delivered to the skin by passing through the membrane.
  • the flux of the drug through the skin (J) is approximated by the following equation:
  • the present invention provides an improved, bi-layer, transdermal device in which the drug is loaded into a polymer gel network, which is applied to a backing.
  • the polymer gel network is a responsive polymer gel network, and no rate- limiting membrane is required.
  • the polymer gel network is also bioadhesive (see Example 19).
  • Polymer gel networks of the present invention can be loaded with very high levels (exceeding 20% by weight) of a biologically active compound (i.e. a drug; see above and see also USSN 08/276,462, filed July 18, 1994 and incorporated herein by reference).
  • a biologically active compound i.e. a drug; see above and see also USSN 08/276,462, filed July 18, 1994 and incorporated herein by reference.
  • the polymer gel network is loaded with at least about 20% by weight of a biologically active compound.
  • Such a preferred transdermal device of the present invention offers increased flux (relative to current transdermal devices) of biologically active compound across the skin, due to the increased loading of the drug into the polymer gel network.
  • Iontophoretic devices made of KATP polymers are also within the scope of the invention.
  • Iontophoretic function of a KATP polymer gel netwoik of the invention may conveniently be studied in vitro in a commercially available Franz-type transport cell.
  • a KATP polymer gel of the invention is loaded with a drug according to any procedure, preferably those described herein.
  • the loaded gel is placed in the reservoir of a well type electrode.
  • the upper (donor) portion of the cell is separated from the buffer-filled bottom (receptor) portion by a membrane (e.g. porcine skin or a synthetic membrane).
  • a membrane e.g. porcine skin or a synthetic membrane.
  • current is applied to the anode which drives the positively charged drug through the membrane into the receptor solution.
  • the amount of drug in the receptor solution is assayed using, for example, HPLC (see, for example, U.S. Patent 4,141,359, incorporated herein by reference).
  • a biologically active compound is loaded into a safe polymer gel network that is responsive to the application of an electric field.
  • delivery of the drug is coordinated with the volume change (e.g. collapse) of the gel, and the drug is not released from the device until exactly the time that the electric field is applied to encourage the drug through the de ⁇ nis.
  • Safe polymer gel compositions of the present invention can also be utilized in internal delivery formulations, for example to allow controlled release of biologically active compounds that are desirably administered at regulated times.
  • Internal delivery formulations are those that allow for delivery of a compound within the body of a subject, and can include oral delivery formulations, injectable formulations, implantable formulations (e.g. transdermals), etc. Internal delivery formulations discussed in this section are those that are not specifically addressed elsewhere in the present specification.
  • compositions are provided that can be implanted in the body and activated by an externally-controlled source (e.g. a magnetic field, an electric filed, pressure, etc.) to release, for example, a pain-killer, only when it is specifically required.
  • an externally-controlled source e.g. a magnetic field, an electric filed, pressure, etc.
  • Such compositions can also be used for controlled release of compounds that are administered cyclically, at predetermined intervals (e.g. insulin, hormones, nitroglycerin, compounds whose administration is related to Orcadian rhythms, etc.).
  • Safe polymer gel compositions of the present invention can be utilized to deliver any biologically active compound internally.
  • internal vaccine delivery compositions are provided, formulated, for example, for delivery by injection or by ingestion.
  • Safe polymer gel compositions of the present invention are also desirably prepared in formulations designed for agricultural delivery.
  • One of the problems associated with delivery of agricultural products e.g. fertilizers, herbicides, etc.
  • One of the problems associated with delivery of agricultural products is that many of the compounds utilized pose health hazards to the workers responsible for applying them.
  • Incorporation of the hazardous compounds into safe polymer gel networks of the present invention avoids exposure of handlers to the chemicals.
  • the compounds are incorporated into responsive gel networks, and are released in response to a stimulus (e.g. magnetic field, magnetic field, rain, sunshine, pH, etc.).
  • a stimulus e.g. magnetic field, magnetic field, rain, sunshine, pH, etc.
  • Medical Instruments Electrodes and other monitoring instruments may have polymer gels of the present invention incorporated within or on the electrode.
  • the gel may have materials such as ligands, enzymes, and the like, immobilized in or on the gel network (see, for example, U.S. Patent 4,274,420, incorporated
  • Polymer gels of the present invention can also be incorporated into or onto other medical instruments such as, for example, the tip of a balloon catheter, a stent, an intervertebral disc nucleus, etc.
  • the polymer gel network need not coat the entire surface of the device.
  • Loading of a drug into, a safe polymer gel network that is incorporated into or onto a medical device can protect the activity of the drug until it is delivered, at the desired time and location.
  • Such a compound can be incorporated into a safe polymer gel network, and preferably a responsive polymer gel network and affixed, for example, to the tip of the balloon catheter.
  • the polymer gel compositions can provide cushioning and or increased lubricity to the coated instruments.
  • a safe polymer gel network of the present invention is formed, through the production of "polyelectrolyte complexes" on the surface of a medical device (see, for example,
  • a drug can be loaded into the gel by any available method including those described herein.
  • the drug is loaded into the gel when the gel is swelled in the presence of the drug.
  • the coated medical device is then positioned in or on a subject, and the drug is delivered to the subject.
  • the safe polymer gel netwoik that is coated on the device is a responsive polymer gel network, and the drug is delivered to the subject when the gel in response to an environmental stimulus.
  • the safe polymer gel network is a responsive polymer gel network
  • the drug is delivered when the gel network is expanded, so that pores open in the gel network and the drug escapes.
  • One of ordinary skill can readily select an appropriate type of gel, with desired responsive characteristics, depending on the type of drug to be delivered, the type of environment into which the drug is to be delivered, the length of time over which the drug is to be delivered, etc.
  • the safe polymer gel networks used to coat medical devices be responsive polymer gel networks.
  • a drug can be loaded into a non-responsive polymer gel network on the surface of a medical device, and can be encapsulated therein, so that the drug is maintained within the polymer gel until the encapsulation is broken by, for example, mechanical force or other means (see, for example, Example 18).
  • Safe, responsive, polymer gel networks of the present invention can also be prepared in cell culturing formulations, for use as a bed material from which cultured cells are readily released.
  • cultured cells are typically collected or detached from the material on which they are cultured through proteolytic (e.g. with trypsin) or chemical treatment (e.g. with EDTA).
  • proteolytic e.g. with trypsin
  • chemical treatment e.g. with EDTA
  • an environmentally-responsive cell culturing material has been described, from which cells can be released by inducing collapse of a poly(N-isopropylacrylamide) gel (see, for example Okano et al. U.S. Patent No. 5,248,766; Okano et al. J. Biomed. Mat. Res.
  • a safe polymer gel network of the present invention and preferably a safe, responsive polymer gel network of the present invention, is physically and/or chemically coated on a solid support (e.g.
  • the cell culturing material of the present invention can be utilized in either of two distinct ways. First of all, cells can be cultured on a shrunked, or collapsed gel, and then can be released from the gel when the gel expands (see Okano et al. , Okano et al. , and Yamada e al., supra).
  • the safe polymer gel utlized in the cell culturing system iof the present invention is a respnsive gel.
  • cells are cultured on the polymer gel netowrk at a temperature above the LCST of the network, so that the network is collapsed. After a period of time, the temperature is decreased to a point below the LCST, so that the gel expands and the cells are released.
  • cells are cultured on an expanded responsive gel, and cell release is induced by triggering collapse of the gel network in response to the appropriate environmental stimulus (see Okano et al., Okano et al., and Yamada e al., supra).
  • Polymer networks and biologically active compounds that are incorporated in, or on, the network may be used in pharmaceutically-effective amounts, with or without a compatible carrier.
  • carrier includes any liquid, gel, fluid, ointment, cream, lotion or the like, which is suitable for use in, or on a subject and which does not interact with the other components of the polymer network in a deleterious manner.
  • compatible means that the components of the pharmaceutical compositions are capable of being commingled with the polymer network of the present invention, and with each other, in a manner such that there is no interaction which would substantially reduce the pharmaceutical efficacy of the pharmaceutical.
  • a "pharmaceutically-effective amount" of a biologically active material or polymer network containing the material is that amount which produces a result or exerts an influence on the particular condition being treated.
  • substances which can serve as pharmaceutically-acceptable carriers are sugars such as lactose, glucose and sucrose; starches such as corn starch and potato starch; cellulose and its derivatives, such as methylcellulose, hydroxypropyl-methyl-cellulose, sodium carboxymethylcellulose, ethylcellulose, cellulose acetate; powdered tragacanth; malt; gelatin; talc; stearic acid; magnesium stearate; calcium sulfate; vegetable oils such a peanut oil, cottonseed oil, sesame oil, olive oil, corn oil and oil of theobroma; polyols such as propylene glycol, glycerine, sorbitol, mannitol, and polyethylene glycol; sugar; alginic acid; pyrogen-free water; isotonic saline; phosphate buffer solutions; cocoa butter (suppository base); emulsifiers, such as the TWEENs * ; as well as other non-toxic compatible substances used
  • NSAID's e.g. NSAID's; pain killers; muscle relaxants
  • local anesthetics e.g. benzyl alcohol; lidocaine
  • Adhesive formulations may also be incorporated into the polymer gels of the invention. Exemplary adhesive devices are described in U.S. Patents 3,972,995 and 4,593,053, incorporated herein by reference.
  • the formulations include, but are not limited to, those suitable for oral, buccal, rectal, topical, nasal, ophthalmic (for example, see U.S. Patent 2,976,576 to a contact lens composition, incorporated herein by reference) or parenteral (including subcutaneous, intramuscular and intravenous) administration, all of which may be used as routes of administration for practicing the present invention.
  • suitable routes of administration include intrathecal administration directly into spinal fluid (CSF), direct injection onto an arterial surface to prevent re-stenosis, and intraparenchymal injection directly into targeted areas of an organ.
  • Formulations of the present invention suitable for oral administration may be presented as discrete units such as capsules, cachets, tablets or lozenges, each containing a predetermined amount of the potentiating agent as a powder or granules; as liposomes containing a loaded gel; or as a suspension in an aqueous liquor or non-aqueous liquid such as a syrup, an elixir, an emulsion or a draught.
  • Formulations suitable for parenteral administration conveniently may comprise a sterile emulsion or a sterile aqueous preparation of the active compound, which is preferably isotonic with the blood of the recipient.
  • Nasal spray formulations comprise purified aqueous solutions of the active compound with preservative agents and isotonic agents. Such formulations are preferably adjusted to a pH and isotonic state compatible with the nasal mucous membranes.
  • Formulations for rectal administration may be presented as a suppository with a suitable carrier such as cocoa butter, or hydrogenated fats or hydrogenated fatty carboxylic acids.
  • Ophthalmic formulations can be prepared by a similar method to the nasal spray, except that the pH and isotonic factors are preferably adjusted to match that of the eye.
  • the formulations of this invention may further include one or more accessory ingredient(s) selected from diluents, buffers, biocides (e.g. chlorhexidine gluconate, triclosan, povidine-iodine, and the like), adhesives (e.g. lectin, pectin, fibronectin, and the like), flavoring agents, binders, anti-microbials, skin permeation enhancers, disintegrants, surface active agents, thickeners, lubricants, preservatives (including antioxidants), surfactants, and the like.
  • biocides e.g. chlorhexidine gluconate, triclosan, povidine-iodine, and the like
  • adhesives e.g. lectin, pectin, fibronectin, and the like
  • flavoring agents e.g. lectin, pectin, fibronectin, and the like
  • binders e.g. lectin, pectin,
  • the pharmaceutical compositions may be in the form of a sterile injectable aqueous or oleaginous suspension.
  • This suspension may be formulated according to known methods using those suitable dispersing or wetting agents and suspending agents which have been mentioned above.
  • the sterile injectable preparation may also be a sterile injectable solution or suspension in a non-toxic parenterally-acceptable diluent or solvent, for example as a solution in 1,3-butane diol.
  • the acceptable vehicles and solvents that may be employed are water, Ringer's solution and isotonic sodium chloride solution.
  • sterile, fixed oils are conventionally employed as a solvent or suspending medium.
  • any bland fixed oil may be employed including synthetic mono-or diglycerides.
  • fatty acids such as oleic acid find use in the preparation of injectibles.
  • the KATP polymer gels of the present invention may be fabricated into a cosmetic compositions by combining the gel with fragrance or other cosmetic material and incorporate the gel into a cosmetic carrier.
  • the cosmetic carrier may take the form of fatty or nonfatty creams, milky suspensions or emulsion-in-oil or oil-in- water types, lotions, gels or jellies, colloidal or noncolloidal aqueous or oily solutions, pastes, aerosols, soluble tablets or sticks.
  • the carrier contains from about 0.001 % to about 10% by weight of the gel of the invention. Preferred ranges are about 0.1 % to about 10 % .
  • Cosmetic compositions according to the invention may also combined with surface active agents of the anionic, cationic or nonionic type, emulsifying agents, perfumes, solvents, fats, oils and mineral wax, fatty acids and derivatives thereof alcohols and derivatives thereof, glycols and derivatives thereof, glycerol and derivatives thereof, lanolin, beeswax, oleic acid, spermaceti, almond oil, castor oil, sorbitol and derivatives thereof, tragancanth gum, clay, magnesia, talc, metal stearates, chalk, magnesium carbonate, and the like.
  • surface active agents of the anionic, cationic or nonionic type emulsifying agents, perfumes, solvents, fats, oils and mineral wax, fatty acids and derivatives thereof alcohols and derivatives thereof, glycols and derivatives thereof, glycerol and derivatives thereof, lanolin, beeswax, oleic acid, spermaceti, almond oil
  • compositions used according to the present invention are given in Example 10.
  • the cosmetic compositions used in the method according to the invention may also contain agents such as antibiotics, anti-inflammatories or anesthetics such as carbenicillin, chloramphenicol, gentamicin, penicillin G, polymyxin B, streptomycin, sulfacetamide, trif-uridine, acyclovir, sulfadiazine, corticosteroids, nystatin, and miconazole.
  • agents such as antibiotics, anti-inflammatories or anesthetics such as carbenicillin, chloramphenicol, gentamicin, penicillin G, polymyxin B, streptomycin, sulfacetamide, trif-uridine, acyclovir, sulfadiazine, corticosteroids, nystatin, and miconazole.
  • the cosmetic compositions of the present invention may all contain various preservatives such as, butylated hydroxytoluene, methionine, cysteine, ascorbic acid, catalase, superoxide dismutase, glutathione, parabens and the like.
  • a microcapillary pipette of about 340 ⁇ m bore (Fisher Scientific, Cat. No. 21-
  • 16A-2A was dropped into the solution.
  • a gel formed in and around the pipette in about 3 hours.
  • the pipette was then removed from the gel and placed in a vessel containing an excess of deionized water (MiUipore Alpha-Q). After about 8 hours the water was decanted off, and the vessel filled with methanol (ACS grade). The pipette containing the gel was allowed to sit in methanol solution for 5 hours. This was followed by three more, 5 hour methanol washes.
  • the pipette was mounted in an airspace of a small, clear capsule (about 5cmx4cmx2cm). Temperature of the capsule was regulated by equilibrating it with well stirred, temperature controlled water solution.
  • a differential thermocouple arrangement permitted the monitoring of temperature differences between water and air within the capsule to about 0.005 deg.
  • the diameter of the gel cylinder was observed at each pH and recorded through the optically clear walls of the capsule using a 10X microscope. Volumetric ratio changes of the gel with pH were determined by cubing the ratio of the gel string diameter to pipette bore.
  • the pH solution was changed every 0.5 pH units and maintained to let the gel reach equilibrium. Then, the volume of the gel was measured. Water temperatures differed by no more than 0.1 °C during the experiments and was maintained at 25 °C. Low pH values were obtained by adding concentrated hydrochloric acid in increasing amounts to the pure, distilled water in one container. Above the pH value for pure, distilled water lacking any acid addition (pH 6), the second container was employed and sodium hydroxide (1 N) was added. The pH was controlled by flowing dry nitrogen gas slowly through the headspace of each container to maintain a positive pressure and prevent entrance of ambient air into the container. The pH was recorded continuously in each container by an Orion combination pH electrode (#91-56) immersed in the solution connected to an Orion #520 pH meter.
  • N-Methyl Pyrolidone (Fisher Scientific, Catalog No. 03688- 4) was added to 5 grams of Modified Food Starch (National Starch, #6818:77-3), and was mixed for 2 hours at 45 °C, while covered, to achieve a clear straw-colored solution. This solution was then placed in a refrigerator for 1 hour in order to achieve a solution temperature of 4-8 °C. To this solution, while stirring, 1 mL of cold (2-8°C) adipoyl chloride (Aldrich, Cat. No. 16,521-2) was added, and the resulting solution was allowed to stir for 1 minute. A gel formed in 12 hours.
  • the gel was then removed, cut into lxlxl cm 3 cubes, and placed in an excess of deionized water (MiUipore Alpha-Q). After 12 hours the water was decanted off, and the vessel was filled with an excess of methanol (ACS grade), and the cubes were allowed to sit in methanol solution for 12 hours. This was foUowed by 3 more 12 hour washes. The cubes were then dried in a desiccator, and then swoUen in deionized water.
  • Example 1 After 12 hours the water was decanted off, and the vessel was fiUed with an excess of methanol (ACS grade), and the cubes were aUowed to sit in methanol solution for 12 hours. This was f Uowed by 3 more 12 hour washes. The cubes were then dried in a desiccator, and then swoUen in deionized water. The pH responsiveness of this material was assayed by preparing the identical gel in pipettes according to the procedures of Example 1. The pH sensitivity was tested using the procedures and apparatus of Example 1 as weU.
  • N-Methyl PyroUdone (Fisher Scientific, Catalog No. 03688- 4) was added to 5 grams of hydroxypropylceUulose (Aqualon, Klucel 99-EF NF) and was mixed for 2 hours at 45 °C, whUe covered, to achieve a clear straw-colored solution. This solution was then placed in a refrigerator for 1 hour in order to achieve a solution temperature of 4-8 °C. To this solution, whUe stirring, 1 mL of cold (2-8 °C) succinyl chloride (Aldrich, Cat. No. S645-2) was added, and the resulting solution was aUowed to stir for 1 minute. A gel formed in 12 hours.
  • the gel was then removed, cut into lxlxl cm 3 cubes, and placed in an excess of deionized water (MiUipore Alpha-Q). After 12 hours the water was decanted off, and the vessel was fiUed with an excess of methanol (ACS grade), and the cubes were aUowed to sit in methanol solution for 12 hours. This was foUowed by 3 more 12 hour washes.
  • the cubes were then dried in a desiccator, and then swoUen in deionized water.
  • the pH responsiveness of this material was assayed by preparing the identical gel in pipettes according to the procedures of Example 1. The pH sensitivity was tested using the procedures and apparatus of Example 1 as weU.
  • EXAMPLE 6 Preparation of HydroxyethylceUulose Gel with Adipic Acid Reagent Exactly, 45 mL of DMSO (Fisher Scientific, Catalog No. 03688-4) was added to a distillation flask containing 5 grams of hydroxyethylceUulose (Aqualon, Natrosol 99-250HBR PA) and 2 grams of adipic acid (Fisher Scientific, Catalog No. A44-500), and was mixed for 2 hours, while covered, to achieve a clear colorless solution. To this solution, 5 mL of toluene (Fisher Scientific), solution was added.
  • DMSO hydroxyethylceUulose
  • 1,2,3,4-butanetracarboxyUc acid Aldrich Chemical, Cat. No. 25,730-3
  • DMSO solution was added, foUowed by the addition of 5 mL of toluene. This solution was aUowed to react under azeotropic distillation (see Haslam Tetrahedron 36:2409, 1980). After 12 hours, a gel formed in the flask. The gel was then removed, cut into lxlxl cm 3 cubes, and placed in an excess of deionized water (MiUipore Alpha-Q). After 12 hours the water was decanted off, and the vessel was fiUed with an excess of methanol (ACS grade), and the cubes were aUowed to sit in methanol solution for 12 hours. This was foUowed by 3 more 12 hour washes. The cubes were then dried in a desiccator, and then swoUen in deionized water. This gel is pH sensitive.
  • EXAMPLE 10 Preparation of HydroxyethylceUulose Gel with Sebacic Acid Reagent Exactly 45 mL of DMSO (Fisher Scientific, Catalog No. 03688-4) was added to a distillation flask containing 5 grams of hydroxyethylceUulose (Aqualon, Natrosol 99-250HBR PA) and 2 grams of sebacic acid (Aldrich Chemical, Cat. No. 28,325-8), and was mixed for 2 hours, whUe covered, to achieve a clear colorless solution. To this solution, 500 ⁇ L of a 50% (v/v) solution of H 2 SO 4 in DMSO solution was added, foUowed by the addition of 5 mL of toluene.
  • a gel containing a fragrance or an active ingredient according to the present invention includes the foUowing materials: a) distiUed water: 65.1 % ; crosslinked KATP hydroxypropylceUulose gel: 5.0%; methylparaben: 0.17%; propylparaben: 0.03%; and b) polyoxethylene (20) sorbitan trioleate: 0.3%; sorbitan monooleate: 0.15%; capryUc/capric acid triglyceride: 2.5 % ; and c) distiUed water: 20.1 %; triethanolamine: 0.8%; and d) active ingredient: 5.0%
  • the KATP responsive gel is expanded to incorporate the remaining components.
  • Components of b) are also introduced by expanding the gel.
  • composition d) is added under stirring.
  • the gel is expanded to incorporate aU the remaining components c) and d).
  • Buffer KH 2 PO 4 /Na 2 PO 4 (Buffer Salt, pH 6.86, Fisher Scientific, #B78).
  • Protein Ovalbumin Grade ⁇ (A5253) Sigma Chemical (St. Louis, MO); 2.3 mg protein/mL soln.
  • Second Polymer Polyvinyl Alcohol 87-89% hydrolyzed, Aldrich Chemical (36, 317-0) 10% by weight in loading soln.
  • the loading of ovalbumin into the gel was performed by equilibrating the gel in an ovalbumin solution. Ten mL of PVA or ovalbumin/PVA solution were added to 20 mL glass vials into which the HPC gels were placed. One gel disc (3.5 mg total weight) were placed in each vial. The gels and vials were stored at room temperature in a desiccator jar and the weights of the gels were recorded vs time. A blot and dry method was used to weigh the gels. Once a constant weight was obtained, the gels were assumed to be equUibrated. Once equUibrated with the appropriate solutions, the gels were removed from solution and placed in a desiccator jar to dry. The ovalbumin content was determined by mass balances. The amount of ovalbumin absorbed by the gel was assumed to be the difference between the dry loaded gel weight and the initial dry gel weight for gels loaded with, and without, PVA.
  • the estimated ovalbumin loaded is the difference between these numbers, or about 97 % . Thus, almost aU of the ovalbumin was loaded into the HPC gels.
  • the ovalbumin released from the dry gels was determined as foUows:
  • the phosphate buffer solution was used to leach out the ovalbumin from the ovalbumin- loaded gels.
  • Three mL of phosphate buffer was placed in glass vials.
  • a defined volume of released solution was removed from the original solution.
  • This volume of released sample was placed in a vial.
  • an identical volume of fresh phosphate buffer was placed back into the original releasing media. Therefore, a constant volume was maintained for the release experiments. This process was continued for approximately 10 hours of regulated sampling, with samples taken every 20 minutes for the first 2 hours and then every hour. This particular technique aUowed for assay of total amount of released ovalbumin.
  • EXAMPLE 14 Loading and Release of Amylase from HPC Gels The loading of ⁇ -amylase into HPC hydrogels was performed by the same method as for ovalbumin with the foUowing reagents:
  • Buffer KH 2 PO 4 /Na 2 -?O 4 (Buffer Salt, pH 6.86, Fisher Scientific, #B78).
  • Protein ⁇ -amylase, BaciUus subtiUs; mol. wt. 48,450; Calbiochem 1,000,000 units (cat #171568); 1.37 mg amylase/mL, soln.
  • Second Polvmer PEG-PPG Copolymer (50/50 by weight), Pluronic PI 05, mol. wt. approx. 6,500 (BASF Performance Chemicals), 10% by weight in loading soln.
  • a bioactivity assay was performed using a Sigma Chemical Assay Kit #577 (based upon colorimetric measurement of the enzymatic release of p-nitrophenol from the substrate 4,6 ethyUdene (G,)-p-nitrophenol (G,)- ⁇ , D-maltoheptaside).
  • the concentration assay for amylase is run using a UV/VIS spectrophotometer (Shimadzu 160U) at 280 nm.
  • the bioactivity of the ⁇ -amylase was determined at selected intervals, and the concentration of the enzyme was assayed at aU intervals.
  • Characteristic release curves for ⁇ -amylase from the HPC gel revealed a diffusion-controUed release pattern with release as a function of the square root of time showing a linear relationship.
  • the released enzyme maintained at least 40% of its original bioactivity over the release interval of 24 hours.
  • EXAMPLE 15 Forming a Safe Polymer Gel Network Comprising Polyelectrolyte Complexes on a Polyamide Device
  • a safe polymer gel network is formed on the surface of a device made from a polyamide material (e.g. nylon; see Figure 6).
  • the polyamide material is treated with di- or multi-functional isocyanate, preferably according to procedures described by Fan (U.S. Patent No. 5,091,205, issued February 25, 1992, incorporated herein by reference), so that a reactive intermediate (i.e. an intermediate that contains isocyanato groups capable of further reaction- e.g. polyurea) is formed on the surface of the material.
  • a reactive intermediate i.e. an intermediate that contains isocyanato groups capable of further reaction- e.g. polyurea
  • the material is then treated with a polycarboxyhc acid (e.g.
  • polyacryUc acid polymethacryUc acid, chondroitin-6-sulfate, etc.
  • the material is then exposed to one or more polycations (e.g. primary amines, secondary amines, tertiary amines, polyimines, basic polypeptides, and the like, including polyethyleneimine, polyethylenepiperazine, collagen), preferably in an aqueous solution.
  • polycations e.g. primary amines, secondary amines, tertiary amines, polyimines, basic polypeptides, and the like, including polyethyleneimine, polyethylenepiperazine, collagen
  • One of ordinary slriU in the art can readUy select particular di- or multi ⁇ functional isocyanates, polycarboxyUc acids, and/or polycations so that the resultant polyelectrolyte complexes form a polymer gel network that undergoes a volume change in response to a change in environmental condition (e.g. mechanical force, pH, salt concentration/composition, etc.). EnvironmentaUy-triggered collapse or expansion of such polymer gel networks results in the network becoming less or more permeable to drugs.
  • environmental condition e.g. mechanical force, pH, salt concentration/composition, etc.
  • EXAMPLE 16 Forming a Safe Polymer Gel Network Comprising Polyelectrolyte Complexes on a Polyethylene Device
  • a safe polymer gel network is formed on the surface of a device made from a polyethylene material (e.g. low density polyethylene; see Figure 5).
  • the material is exposed to a polycarboxyUc acid in the presence of irradiation energy, so that reaction between the polycarboxyUc acid and the polyethylene results in free carboxylic acid groups extending from the surface of the polyethylene.
  • a polyethylene material e.g. low density polyethylene; see Figure 5
  • the material is exposed to a polycarboxyUc acid in the presence of irradiation energy, so that reaction between the polycarboxyUc acid and the polyethylene results in free carboxylic acid groups extending from the surface of the polyethylene.
  • polyacryUc acid 10-30 w% aq
  • ⁇ - irradiation e.g. by exposure to w Co; dose 0.5 Mrad; dose rate 100 rad sec
  • FeSO 4 (NH 4 ) 2 SO 4 50 mM aq).
  • Example 15 The material is then exposed to a polycation, so that a polyelectrolyte complex forms, as described in Example 15.
  • a polyelectrolyte complex forms, as described in Example 15.
  • polyethyleneimine 10-30 w% aq
  • EXAMPLE 17 Coating a Device with a Safe Polymer Gel Network Comprising Polyelectrolyte Complexes
  • a safe polyelectrolyte complex between a polyacid and a polybase is first formed in an aqueous solution, and is subsequently coated onto a porous support (e.g. mtroceUulose acetate, ceUulose acetate, polyethylene, polypropylene, teflon, etc.) by, for example, casting, precipitation, or impregnation (see Figures 6 and 7).
  • a polycomplex between a polyacid comprising a polycarboxyUc acid and a polybase comprising a polyamine can be crosslinked by intermolecular amide bonding.
  • a safe polymer gel comprising a collagen/chondroitin-6-sulfate (C6S) polyelectrolyte complex onto a polypropylene membrane by mixing collagen (3 g/L of 20 xx 1.5 ⁇ m particles) with C6S (0.2 g/L) for 2-4 hr at pH 7.2 and 4 °C (see Figure 7).
  • the mixture was coated on a polypropylene membrane that had been pre- treated with methanol, and the coated membrane was then immersed in CH 3 COOH (50 mM aq) for 1-2 hours, so that a polyelectrolyte collagen/C6S complex precipitated onto the membrane.
  • the membrane was then placed on a steel surface which was cooled through contact with dry ice, so that the polyelectrolyte complex was frozen onto the membrane. Subsequently, the material was lyophilized (0.05 torr, 24 hours, room temperature, foUowed by 105 °C for 24 hours). Although it is not necessary, the material was subsequently immersed in glutaraldehyde (0.3 w%), in the present of aqueous CH 3 COOH, at pH 3.5 and room temperature, for 24 hours. The resultant coated membrane was stable over a pH range of about 2 to about 10, and also at high ionic strength. Furthermore, the crosslinked polymer gel network was pH-responsive, and aUowed regulation of the permeabiUty of the polypropylene membrane (to drugs and/or other compounds) through controUed expansion or collapse of the gel.
  • EXAMPLE 18 Encapsulation of a BiologicaUy Active Compound in a Safe Polymer Gel Netwoik Coated on an Angioplasty BaUoon
  • Angioplasty baUoons are typicaUy made of nylon, or another polyamide material.
  • such an angioplasty baUoon is treated with an isocyanate, foUowed by a polycarboxyUc acid, as described in Example 15 and in Fan (U.S. Patent No. 5,091,205).
  • Angioplasty baUoons coated with polyacryUc acid are currently available from Boston Scientific (Boston, MA). The coated baUoon then immersed in an aqueous solution of poly(ethylene glycol) (PEG) poly(ethyleneoxide) at pH ⁇ 3.2.
  • PEG poly(ethylene glycol)
  • a PEG/polyacid polymer gel network forms on the surface of the baUoon.
  • proton acceptor polymers e.g. polypropylene glyocol, polypropylene oxide, poly (N,N-dimethylacrylamide)
  • other proton acceptor polymers e.g. polypropylene glyocol, polypropylene oxide, poly (N,N-dimethylacrylamide)
  • the final polymer gel network has an appropriate KATP.
  • the polyacid-coated baUoon is contacted with a drug prior to being immersed in the PEG solution, so that the drug is loaded into the polyacid gel, and in subsequently trapped therein by encapsulation with PEG.
  • the mechanical force exerted by the expanding baUoon breaks the PEG encapsulation, so that pores open in the polyacid gel, and the drug is released.
  • Bioadhesive safe polymer gel compositions of the present invention have been formulated from a variety of different polymer starting materials, including Carbopol * 934P (polyacryUc acid: BF Goodrich), Carbopol * 974P (polyacryUc acid; BF Goodrich), Noveon * AA1 (polycarbopbil; BF Goodrich), Natrosol * 250 HHX
  • the polymer was mixed using a mixer set at 800-1200 ⁇ m. Deionized water was added until the polymer was solubilized. In some cases (e.g. Methocyl K4M), the deionized water was heated before being added.
  • bioadhesive gel formulations have a pH of about 5.0.
  • Any of these bioadhesive formulations can be combined with other safe gel polymer networks (e.g. crosslinked polymer gel networks) of the present invention, for example so that the bioadhesive gel formulation comprises approximately 1-99% of the final gel composition (i.e. the gel composition comprising the bioadhesive gel formulation and another safe polymer gel netowrk of the present invention).
  • Other materials such as compounds that assist in dispersion of crosslinked polymer gel networks, can also be included in the final gel composition, which can then be loaded with a biologicaUy active compound as described herein.

Abstract

Réseau de gel polymère réticulé et sensible, comprenant des chaînes polymères reliées par l'intermédiaire d'un agent de réticulation multifonctionnel. Les chaînes polymères et l'agent de réticulation présentent un profil toxicologique connu et acceptable (KATP). On décrit des procédés permettant de déterminer si une matière donnée présente un profil toxicologique connu et acceptable. Les chaînes polymères, ainsi que l'agent de réticulation, devraient être un composant d'un produit qui est considéré comme satisfaisant aux règlements en vigueur émanant d'agences gouvernementales et régissant l'utilisation de ce produit dans les domaines relatifs à l'alimentation, à la cosmétique et à l'administration de médicaments aux animaux.
PCT/US1995/009815 1994-07-18 1995-07-18 Nouveaux reseaux de gel polymere et procedes d'utilisation WO1996002276A2 (fr)

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