Title of Invention	A PROCESS FOR THE PREPARATION OF A BIOCOMPATIBLE POLYMERIC COMPOSITION OF AN INTER-PENETRATING POLYMERIC NETWORK(IPN)
Abstract	A process for the preparation of a biocompatible polymeric composition of an inter-penetrating polymeric network <IPN) comprising dissolving 70-90X of a biocompatible polyurethane in an organic solvent to form a solution, followed by dissolving 10-Z&% of a vinyl monomer, an initiator in a proportion of 1-2*/. by weight of the vinyl monomer and a cross 1 inker in a proportion of 1-2% by weight of the vinyl monomer in the solution to form a homogeneous mixture« followed by curing the same to obtain the biocompatible polymeric composition of an interpenetrating polymeric network (IPN).

Title of Invention

A PROCESS FOR THE PREPARATION OF A BIOCOMPATIBLE POLYMERIC COMPOSITION OF AN INTER-PENETRATING POLYMERIC NETWORK(IPN)

Abstract

A process for the preparation of a biocompatible polymeric composition of an inter-penetrating polymeric network <IPN) comprising dissolving 70-90X of a biocompatible polyurethane in an organic solvent to form a solution, followed by dissolving 10-Z&% of a vinyl monomer, an initiator in a proportion of 1-2*/. by weight of the vinyl monomer and a cross 1 inker in a proportion of 1-2% by weight of the vinyl monomer in the solution to form a homogeneous mixture« followed by curing the same to obtain the biocompatible polymeric composition of an interpenetrating polymeric network (IPN).

Full Text	FIELD OF THE INVENTION This invention relates to a composition of an interpenetrating polymeric network for the treatment of diabetes mel1itus and a process for the preparation thereof. This invention further relates to a composition of an interpene¬trating polymeric network (IPN) for preparing retrievable, inartificial implant for the treatment of diabetes mel1itus. BACKGROUND OF THE INVENTION Type I diabetes an autoimmune disorder of endocrine pancreas is a major health concern worldwide and has long term systemic complications. Transplantation of isolated insulin-secreting islet cells of langerhans is a comparatively recent approach^ which is easier and safer than whole pancreas transplantation. However^ immunosuppression is one of the major concerns of such transplant procedures. Critical shortage of donor islet cells is another concern in such technology. It is hence desirable to use Biohybrid devices that employ synthetic semipermeable membranes to encapsulate islet cells and allow the use of alio or xeno origin cells. The membranes are expected to permi t the crossover of low molecular weight substances such as nutrient electrolytes, oxygen and bio-secretor products but not of transplant effectors. Polymeric membranes such as alginate-poly (L-lysine >, polycar¬bonate* polyvinyl chloride - acrrylic copolymers, poly (2-hydroxy ethyl methacrylate)5 agarose, polyvinyl alcohol have been proposed as immunoisolation matrices. Such membranes have been used in various device configurations including microcapsules, AV shunts^ hoi low fibers and planar diffusion chambers• However, fibrotic react ions» biocompatibllity, mechanical fragility and reduced permeation have been reported to be the 1imiting -factors for the widespread use of these candidate materials* It is the basic requirement that the membrane materials should exhibit satisfactory biocompatibllity, ie. the ability of the material to induce minimal inflammatory response in the host's tissue resulting in acceptance of the implant without altering its function. For a successful application of this technology, the ability to retrieve a material, which may not function to the best possible response, should also be possible. Degraded microcapsules of encapsulating membranes or non-functional islets that cannot be retrieved may pose a problem in the long term by inducing antigenic reactions. OBJECTS OF THE INVENTION It is therefore an object of this invention to propose a bio¬compatible polymeric composition which does not induce fibrotic reactions. It is a further object of this invention to propose a bio¬compatible polymeric composition which is easily retrievable- Another object of this invention to propose a bio-compatible polymeric composition which is effective for the treatment of diabetes without immunosuppression« Yet another object of this invention to propose a bio-compatible polymeric composition for immunoisolating encapsulated ^ islet cells within the membranes and which permit the cells to be V1ab1e * Other objects and advantages of the invention will be more apparent from the ensuing description• BRIEF DESCRIPTION OF THE INVENTION Thus according to this invention is provided a biocompatible polymeric composition of an interpenetrating polymer network comprising a biocompatible polyurethane and a biocompatible vinyl polymer. According to this invention is further provided a process for the preparation of a biocompatible polymeric composition of an inter¬penetrating polymeric network of a biocompatible polyurethane in an organic solvent to form a solut ion 9 f ol lowed by dissolving 1(?>""3^VJ of a vinyl monomer ^ an initiator in a proportion of l"2y» by weight of the vinyl monomer and a crosslinker in a proportion of 1-2% by weight of the vinyl monomer in the solution to form a homogeneous mixture» followed by curing the same to obtain the biocompatible polymeric composition of an interpenetrating polymeric network In accordance wi th this invention f a 70-90/f solution of a bio- compatible polyurethane is prepared by dissolving the poly- urethane in a good solvent for it such as tetrahydrofuraoi dimethyl formamide« dimethyl acetamide to form a homogeneous solution? either at room temperature or by heating in the range o of 60-70 C and stirringi if necessary. A monomer of the second polymer is chosen from a group of either hydrophobic or hydro-philic vinyl monomers and a weight fraction of i0-Z0% of the same is dissolved in the same chosen solvent for the polyurethane and stirred together so as to form a homogeneous mixture. An initiator of the monomer of the second polymer is chosen from a group of either free radical or redox or other initiator for a vinyl monomer and a weight fraction of 1-2% of the second monomer concentration dissolved in the same chosen solvent for the poly¬urethane and stirred together so as to form a homogeneous mixture. Further» a crosslinker of the second polymer9 which may be another smal1 molecule with a vinyl group in it such as ethylene glycol dimethacrylate» N,N' bis acrylamide, etc. at a weight fraction of 1-254 of the second monomer concentration 9 is dissolved in the satne chosen solveTit for the polyurethane and stirred together so as to form a homogeneous mixture The mixture a is allowed to cure together in a mold for 24-48 hours at 60-75 C. The IPN is formed by comfain-ation of two polymers where the first polymer is a polyurethane and the second polymer is a vinyl polymer. The polyurethane is a 1inear segmented polyurethane which has hard and soft segments with a polyol as the soft segment and a diol or diamine as the chain extender- The poly-* urethane may be either aliphatic or aromatic in nature. The second polymer is a vinyl polymer which may be from a group which is either a hydrophilic or hydrophobic. The second polymer may be from a group such as polyvinyl pyrrolidone, polymethyl methacrylate» polyacrylamide* poly-hydroxyethyl methacrylate and poly ethyl hexyl acrylate. In accordance with an embodiment of this invention is provided flat membrane sheets of the interpenetrating polymer network and a method for the preparation of the same comprising dissolving lj?i-50/ by weight of the cured IPN in an organic solvent* such as tetrahydrofuran, dimethyl formamide f dimethyl acetamide to form a homogenous solution either at room temperature or by heating in o the range of 60--70 C and stirring, if necessary. The solution of the IPN may have a concentration from 10-^0% of polymer in solvent The IPN solution is then cast in a mold as a flat m&n±trane sheet. The IPN cast as sheet is then alloiij^d ttD contact air for an hour. The partially cured membrane is then contacted with ice cold water for 24 hrs. and later removed from mold and o cured at 60 C in an oven and by immersing in water. This is followed by extraction with solutions of hexane and ethanol-water mixtures and distilled water to remove unreacted components from the membrane. In accordance with a further embodiment 9 the IPN solution is made into a porous tube by coating on a plastic mandrel once in the solution and withdrawing. The mandrel is then inverted and allowed to cure by contacting air for 1 hr-. It is then dipped in ice cold water for 15 mins. to form the first coat layer of IPN1 The first coat IPN mandrel is dipped in the IPN solution for the second time to form the second layer. The procedure is continued till multiple layers, for eg. five consecutive layers of IPN are obtained. After which the mandrel is left in ice cold water for 24 hrs. The, IPN coated as tube is removed from mandrel inside out to form the porous tube of the invention. According to further embodiments9 cylinders or other shapes may be obtained. The membrane is selectively permeable to cell nutrients, meta¬bolites and waste molecules of less than 60,000 molecular weight and impermeable to the higher molecular weight immunoglobulins of greater than 66,000 molecular weight. It has open interconnected pores of 5-10 micron size in diameter, with a majority of the pores being 5-micron size. The IPfi membranes of the invention are retrievable on implantation. In accordance with a still further embodiment of this invention, IPN biohybrid islet implant and a method for implantation is provided which reverses the diabetic state of mice models- The isolated islet cells are suspended in a alginate gel, formed by mixing a solution of sodium alginate solution containing the islets with a calcium chloride solution, and the gel containing islets is introduced in an IPN porous tube of the invention or flat sheet membrane pouch of the invention. The IPN porous tube or flat sheet device of the invention containing the gel with islets is sealed with the IPN solution and pressure, or sealed by applying a hot seal and pressure. The biohybrid IPN-islet implant is implanted in the peritoneal cavity of diabetic mice and allowed to reverse the diabetic state of the mice. The implantation of the biohybrid implant of the invention is not restricted to the peritoneal site but covers all other sites of implantation in animal or human bodies. Further, the IPN of the invention is not restricted to use with islet cells alone but also for any other cell type requiring immunoisolation prior to transplantation, eg. hepatocytes^ dopamine producing cells, chromaffin cells, etc.. The IPN of the invention is also not restricted to the permeation of molecules necessary for the treatment of diabetes, but also to the permeation of all mol Gcules within the range of upto 60,^00 molecular weight and may relevant to the^ treatment of any type of disease that my require the use of immunoisolation techniques. The invention will now be explained in greater detail with the heIp of non-1imi ting examples. Example 1: A polymeric composition of an IPN material comprising an aliphatic polvurethane and a hvdrophilic vinvi polvmer( PU-PVP Semi IPN) A1. Synthesis of the aliphatic linear segmented polyurethane A molar concenteration of an aliphatic diisocyante such asHydrogenated methylene bisdiisocyanate (HMD!) is taken in a 3 necked flask or polymer reactor fitted with a stirrer and a condenser. A stoichiometric molar amount of the polyol, polytetramethylene ether glycol, is added dropwise to the stirred HMDI solution in an atmosphere of nitrogen. 0,2 wt% of a catalyst dissolved in a small amount of the solvent N,N, dimehtylacetamide was added to the reaction flask. Reaction is carried out at 60'C for an hour. Theteactant mixture consisting of a prepolymer is cooled and chain extended with addition of a chain extender such as butanediol with stirring* Stoichiometric quantities of the polyol, chain extender and diisocyanate are selected so as to have a final NC: OH ratio of 1.1 and is well known to those skilled in the art The temperature of the reactant mixture is raised to 60^C for an hour more and reactant mixture is transferred to a polyethylene mold in an oven, in the form of a thin film, for further curing of 48 hours at 60^C B1, Synthesis of the aliphatic- hydrophic -PU-PVP Semi IPN : ( PU-PVP 10% SemlPU) AID wt% solution of tt% poiyur^hane in solvent dlmethylacetamide, prepared by dissolving the polyurethane prepared as in (a) above in the solvent is mxed with an amount of N- Vinyl pyrrolidone monomer, such that the final ration of polyurethane to vinyl monomer is 90:10, An Initiator for vinyl polymers such as azobisisobutyronitrHe (AIBN) at a conceftteration of 1 wt% o#^ vinyl mondfln^r, and crosslinker for vinyl polymers such as ethyteig^col dimethacrylate at a concenteration of 1-3% of the vinyl monomer is added to the iWxture. The entire mixtufd Is Introduced in the polyethylene niold and cured at 80°C for 2 hours and further 60°C for 24 hours In an oven. Alternate procedure: A2. Linear aliphatic segmented polyurethane Any biocompatible grade linear segmented polyurethane of molecular weight of atleast > 60000 and known to be prepared from aliphatic diisocyanate, commercial samples like Tecoflex 60 D, Chronoflex etc are examples, is dissolved in a solvent such as N,N dimethyl acetamide at a concenteration ranging from 10-15 wt% to fomi the solution of polyurethane of the Semi IPN. B2. Synthesis of the aliphatic-hydrophilic- PU-PVP Semi IPN : ( PU-PVP 10% Semi IPN) A 10 wt% solution of the polyurethane such as Tecoflex 60 D in solvent dimethylacetamide, prepared by dissolving the polyurethane prepared as in (A2) above in the solvent is mixed with an amount of N- Vinyl pyrrolidone monomer, such that the final ration of polyurethane to vinyl monomer is 90:10. An initiator for vinyl polymers such as azoblsisobufyronitrile (AIBN) at a concenteration of 1 wt% of the vinyl monomer, and crosslinker for vinyl polymers such as ethylenglycol dimethacrylate at a concenteration of 1-3% of the vinyl monomer is added to the mixture. The entire mixture is introduced in the polyethylene mold and cured at 80°C for 2 hours and further 60°C for 24 hours in an oven. Example 2: Semi iPNs of an IPN material comprisino an aliphatic polvurethane and a hvdrophilic vinvl polvmer (PU-PVP Semi IPN) of 80:20 and 70: 30 compositions. For Semi IPNs of polyurethane and N vinyl pyrrolidone of compositions 80:20 or 70:30, the concenterations of the aliphatic polyurethane as in A1 or A2 of example 1 above, is 80 wt% and 70 wt% respectively, and the amount of vinyl monomer added is 20 wt% and 30 wt% respectively. An initiator for vinyl polymers such as azot)isisobutyronitrtle (AIBN) at a concenteration of 1 wt% of the vinyl monomer, arwl crosslinker for vinyl polymers such as ethylenglycol dimethacrylate at a concenteration of 1-3% ofthe vinyl monomer is added to the rriixture. The entire mixture is introduced in the polyethylene mold and cured at SO^C for 2 hours and further 60°C for 24 hours in an oven. Example 3: Semi IPNs of an IPN material comprising an aliphatic polvurethane and a hvdrophilic vinvl polvmer such as polvacrvlamide( RAM) or hvdroxvethvl methacrvlate (PHEMA). For Semi IPNs of polyurethane and polyacrylamide (PAM) of compositions, 90:10; 80:20; 70:30, the concenterations of the aliphatic polyurethane as in A1 or A2 of Examp.le 1 above is 90 wt%; 80 wt% and 70 wt% respectively, and the amount of vinyl monomer such as acrylamlde, hydroxyethyl methacrylate added is 10 wt%; 20 wt% and 30 wt% respectively. An initiator for vinyl polymers such as azoblslsobutyronitrile (AIBN) at a concenteration of 1 wt% of the vinyl monomer, and crosslinker for vinyl polymers such as ethylenglycol dimethacrylate at a concenteration of 1-3% of the vinyl monomer is added to the mixture. The entire mixture is introduced in the polyethylene mold and cured at BO'C for 2 hours and further 60°C for 24 hours in an oven. Example 4: Semi IPNs of an IPN nriaterial comprising an aliphatic polvurethane and a hydrophobic vinvl polvmer such as polvmethvl methacrvlate (PMMA) or polveth vlhexvlacrvlate. PEHA. For Semi IPNs of polyurethane and hydrophobic vinyl monomers of polymethylmethacrylate or polyethyl hexyl acrylate of compositions, 90:10; 80:20; 70:30, the concenterations of the aliphatic polyurethane as in At or A2 of Example 1 above is 90 wt%; 80 wt% and 70 wt% respectively, and the amount of vinyl nrxinomer such as methyl methacrylate or ethyl hexyl acrylate added is 10 wt%; 20 wt% and 30 wt% respectively. An initiator for vinyl polymers such as azobisisobutyronitrile (A16N) at a concenteration of 1 wt% of the vinyl monomer, and crosslinker for vinyl polymers such as ethylenglycol dinoethacrylate at a concenteration of 1-3% of the vinyl monomer is added to the mixture. The entire mixture is introduced in the polyethylene mold and cured at 80*C for 2 hours and further SO^C for 24 hours in an oven. ExaiBfifo SI A polvmeric composition of an IPN material comprising an aron^atic polvurethane and a hvdrophilic vinvl polvmer( PU-PVP Semi IPN) A3. Svnthesis of an aromatic polvurethane 3 moles of toluene diisocyanate was converted to a biuret by adding stoichiometric amount of water in a 3 necked flask fitted with a stirrer and a condenser or polymer reactor in nitrogen atmosphere. The mixture was hated using 0.1 wt % of a catalyst, dibutyltindialaurate for 30 minutes. The white mass of biuret formed was cooled and dissolved in dimethylacetamide as the solvent. A stopichiometeric anwunt of polyol was added to the clear liquid abnd the reaction was carried out for an hour with heating. The contents were cooled to room temperature and the crosslinker such as trimethylol propane was added with vigorous stirring. The mixture was degassed and poured on to a polyethylene mold and cured at 80°C for 2 hours and further 60°C for 24 hours in an oven. B 3. Synthesis of the aromatic - hvdroDhilic (PU-PVP Semi IPN): (PU-PVP10%SemilPN) A 10 wt% solution of the polyurethane in solvent dimethylacetamide, prepared by dissolving the polyurethane prepared as in (A3) above in the solvent is mixed with an amount of N- Vinyl pyrrolidone monomer, such that the final ration of polyurethane to vinyl monomer is 90:10. An initiator for vinyl polymers such as azobisisobutyronitrile (AIBN) at a concenteration of 1 wt% of the vinyl monomer, and crosslinker for vinyl polymers such as ethylenglycol dimethacrylate at a concenteration of 1-3% of the vinyl monomer is added to the mixture. The entire mixture is introduced in the polyethylene mold and cured at 80°C for 2 hours and further 60°C for 24 hours in an oven. Alternate procedure: A5. Linear aromatic segmented polyurethane Any biocompatible grade linear segmented polyurethane of molecular weight of atleast > 60000 and known to be prepared from aromatic dlisocyanate, commercial samples like Biomer are examples, is dissolved in a solvent such as N.N dimethyl acetamide at a concenteration ranging from 10-15 wt% to form the solution of polyurethane of the Semi IPN; B5. Synthesis of the aromatic-hydrophilic- PU-PVP Semi IPN : ( PU-PVP 10% Semi IPN) A 10 wt% solution of the polyurethane in solvent dimethylac^amide, prepared by dissolving the polyurethane prepared as in (A5) above in the solvent is mixed with an amount of N- Vinyl pyrrolidone monomer, such that the final ration of polyurethane to vinyl monomer is 90:10. An initiator for vinyl polymers such as azobisisobutyronitrile (AIBN) at a concenteration of 1 wt% of the vinyl monomer, and crosslinker for vinyl polymers such as ethylenglycol dimettiacrylate at a concenteration of 1 -3% of the vinyl monomer is added to the mixture. The entire mixture is introduced in the polyethylene mold and cured at 80°C for 2 hours and further 60°C for 24 hours in an oven. Example 6: Preparation of a flat membrane bv phase inversion process An IPN prepared by any of the examples above or by other methods known to those skilled in the art is extracted with polar and non polar solvents to remove any unwanted reaction products, mold releasing agents, impurities etc and dried before redissolving in a suitable good solvent such as dimethylacetamide, dimethylformamide etc, at a concentration ranging from 10-20 wt % dependent on the molecular weight of the pdyurethane so as to form a viscous solution. The solution is cast on a flat polyethylene mold in the form of a thin film and allowed to contact air for and hour. The partially cured membrane is next contacted with a nonsolvent such as Ice cold water for 24 hours and removed from the mold. The flat membrane is immersed in a bath of water at 60oC for 5 hours before extensive washing in water and and further use. Example 7: Preparation of a tubular macrocapsule of an aliphatic polvurethane and hvdrophilic polvmer such as PU-PVP 20 wt% IPN bv phase inversion process. A semi IPN formed from an aliphatic polyurethane as in example 1- B2 above is dissolved in the appropriate solvent at a concenteration ranging from 10-20 wt% and giving a viscous solution. A mandrel of a hydrophobic polymer such as Teflon, polyethylene glycol or polypropylene of outer diameter equivalent to the inner diameter of the required macrocapsule is dipped in the viscous solution of the polyurethane. The mandrel is removed from the solution and contacted with air in an inverted position for a time period ranging from 15 minutes to an hour. The coated mandrel is then immersed in ice cold water for a time period ranging from 15 minutes to an hour. Upto 5 alternate coats of IPN solution and water are done this way. Following the last coat of polymer and water, the thin tubular film of the IPN formed on the mandrel is manually removed and turned inside out and immersed in a container containing water at 0-10 ^C, for 24 hours. The tubes are finally extracted with water in several washes before actual use to encapsulate islet cells. Example 8: Encapsulation of islet cells in PU-PVP macrocapsules for treatment of diabetes in animal models. A6. Isolation of pancreatic islet cells from mice BALB/c mice of 10 weeks were sacrificed by cervk:al dislocatkni, pancreas dissected, minced and incubated in 1 mg/ml collagenase P (Boehringer Mannheim, Germany) on a shaker platform for 20 minutes. Freshly isolated islets were then cultured in RPM11640 (GibcoBRL, NY, USA) medium with 10% FCS for 48 h. Islets (n=30) were handpicked and cultured on membranes (1 cm^) in 24 well plate (Nunclon. Denmark) and their morphology observed under phase contrast microscope for 5 days. Viability of islets cultured on membranes was detennined by trypan blue dye exclusion test, using 0.04 % (vwV) trypan blue. Islets staining blue were scored dead while viable islets were those that did not take up the dye. B6 . Encapsulation of mice pancreatic islet cells in PU-PVP macrocapsules Viable islets of (1 IE == 150 ^m diameter islet) were handpicked and washed with Hanks buffer. Islets were suspended in a solution of 2 wt % sodium alginate such that a total concenteration of 500 IE of islets could be introduced through the open end, in each tubular macrocapsule formed from a PU-PVP IPN ( prepared earlier as per example 7 above), of dimensions 3.8mm inner diameter, and enclosing a volume of 200 pi, by addition of 150 pi of the alginate-islet suspension and having one open end. A small amount of calcium chloride solution may or may not be added to increase the viscosity of the alginate gel and prevent free flow of the suspension of islets from the macrocapsule. The open end of the macrocapsule was then sealed with a heat seal and edges of the seal rounded by immersion of the portion of the seal in a solution of the same IPN composition and immediately washing in Hanks buffer. The macrocapsules containing islet cells were stored in Hanks solution before surgery for transplantation was started on the animal models. Example 9: In vivo biohvbrid pancreas transplantation studies Streptozotocine induced diabetic mice were used for the transplantation and monitoring of diabetic status in animal experiments. Animals were fasted overnight and anaesthetized by /.p. administration of thiopental sodium at a dose of 40 mg/kg body weight. A small incision is made in peritoneum and two tubular grafts containing 500 IE (1 IE = 150 ^m diameter islet) each, suspended in 1% alginate gel matrix, were implanted while diabetic control animals received empty tubular grafts. Inct^>ns were sutured using absorbable 6-0 catgut sutures and autoclipper (Becton Dickinson, USA). All animals received an i-p injection of gentamycin (3 nr^g b.w.), ampicittin and ckDxacillin (20 mg/kg b.w.) and diclofenac sodium (0.5 mg/kg b,w.), for 3 days (starting from the operattve day) in addition to the topical ointments (Soframycin). Animals were followed for 14 post-operative weeks with weekly non-fasting blood glucose measurements using glucose oxidase kit (Sigma, USA). On 12^ week post-transplantation, some of the tubuter grafte (n=4) were retrieved to confirm islet graft functloa All animals v^re also subjected to intra peritoneal glucose tolerance test (2.0 g/kg b.w.) at the end of 12^ week post transplantation. The study was carried out in 12 animals and compared to a similar number of control normal mice glucose levels during the sanr^ period. The glucose levels in the diabetic mice which were initially highly elevated couM be brought down to normal levels within 48 hours of implantation of the encapsulated islet macrocapsules. The normal glycemic levels were maintained throughout the period of the study confirming the utility of the system to cure diabetes in a diabetic animal model. No immunesuppressing drugs to avoid the rejection of the transplanted islets was used in this study and the macrocapsule is believed to have selectively perfomed as a barrier for the transfer of Immunoglobulins, cytokines, macrophages and other cells of the host animal that can cause rejection of the transplanted islets. WE CLAIMS 1. A process for the preparation of a biocompatible polymeric composition of an inter-penetrating polymeric network 2. The process as claimed in claim 1 wherein said vinyl polymer is selected from hydrophi1ic and hydrophobic vinyl monomers- 3. The process as claimed in claim I wherein said polyurethane is an aromatic or a aliphatic polyurethane. 4. The process as claimed in claim 3 wherein said polyurethane is a linear segmented polyurethane with hard and soft segments. 5. The process as claimed in claim 4 wherein said polyurethane comprises a polo as the soft segment and a compound selected from a idol and dopamine as the chain extender, 6. The process as claimed in claim 1 wavering said initiator is» such as a free radical 9 redo or any other initiator suitable for vinyl monomers. 7- The process as claimed in claim 1 wherein said cross linker is a molecule with a vinyl group« such as ethylene glycol dimeth-acrylate, N,N'-bisacrylamide. 8. The process as claimed in claim 1 wherein said solvent is an organic solvent« such as tetrahydrofuran, diethyl form amide, diethyl ace amide. 9. The process as claimed in claim 1 wherein said polyurethane is dissolved in the solvent to form a homogeneous solution at room o temperature or by heating at 60-70 C with stirring, if required. 10. The process as claimed in claim 1 wherein curing is effected temperature in the range of 60-75 C. 11. The process as claimed in claim 1 wherein curing is done for a period of 24-48 hrs.. 12. The process as claimed in claim 1 wherein curing is done in a mold • 13. A biocompatible polymeric composition of an inter-penetrating polymer network comprising a biocompatible polyurethane and a biocompatible vinyl polymer. 14. The composition as claimed in claim 13 wherein said vinyl polymer is selected from a group of polymers, such as polyvinyl pyrro-1idone polymethyl methaerylate, polyacrylamide, poly- late and poly-ethyl-hexylacrylate . 15. The composition as claimed in claim 13 wherein the proportion of said polyurethane is 70-90/ and the proportion of the vinyl polymer is 10--30% by weight. 16. The composition as claimed in claim 13 wherein said vinyl polymer is selected from and hydrophobic vinyl monomers. 17. The composition as claimed in claim 13 wherein said polyurethane is an aromatic or a aliphatic polyurethane . 18. The composition as claimed in claim 17 wherein said polyurethane is a linear segmented polyurethane with hard and soft segments, 19. The composition as claimed in claim 18 wherein said polyurethane comprises a polyol as the soft segment and a compound selected from a dial and diamante as the chain extender. 20- A process for the preparation of IPN membranes comprising dissolving 10-50% of the composition of the inter-penetrating polymer network in a solvent and casting the same in a mold as a flat membrane 9 contacting the same with water, followed by removing from the mold» curing the sheet and extracting unseated components from the membrane to obtain IPN membranes. 211, The process as claimed in claim 20 wherein said solvent is selected from tetrahydrofuran, dimethyl formamide, dimethyl acetamide. 22. The process as claimed in claim 20 wherein said composition o of IPN is dissolved at room temperature or by heating at 60-70 C with stirring? if required. 23. The process as claimed in claim 20 wherein the unrelated components are removed by extraction with solutions of hexane 9 ethanol-water mixtures and distilled water. 24. An IPN membrane for immune-isolating living cells. 25. A process for the preparation of IPN porous tube comprising dissolving of an IPN composition in a solvent to form a solution* cationic the isolation on a mandrel followed by inverting the mandrel, curing, dipping in water to form the first IPN layer, repeating the process to form multiple layers, dipping the mandrel and removing the IPN porous tube from the mandrel. 26P The process as claimed in claim 25 wherein curing is effected o at 60-70 C. 27. An IPN porous tube for immune-isolating living cells. 28. A process for producing an IPN biohybrid islet implant comprising suspending isolated islet cells in an alginate gel followed by mixing a calcium chloride solution thereto and intro¬ dicing the gel with the islet cells into an IPN tube or pouch made from IPN membrane, sealing the tube or pouch. 29*, The process as claimed in claim 28 wherein the pouch or tube containing the islet cells are sealed with IPN solution and pressure or by applying a hot seal and pressure. 30. The process as claimed in claim 28 wherein said biohybrid IPN-islet implant is implanted in the peritoneal cavity of diabetic mice and allowed to reverse the diabetic state of the mice. 31 • A biohybrid IPN islet implant for reversal of the diabetic state of mice.

Full Text

FIELD OF THE INVENTION
This invention relates to a composition of an interpenetrating polymeric network for the treatment of diabetes mel1itus and a process for the preparation thereof.
This invention further relates to a composition of an interpene¬trating polymeric network (IPN) for preparing retrievable, inartificial implant for the treatment of diabetes mel1itus.
BACKGROUND OF THE INVENTION
Type I diabetes an autoimmune disorder of endocrine pancreas is a major health concern worldwide and has long term systemic complications. Transplantation of isolated insulin-secreting islet cells of langerhans is a comparatively recent approach^ which is easier and safer than whole pancreas transplantation. However^ immunosuppression is one of the major concerns of such transplant procedures. Critical shortage of donor islet cells is another concern in such technology. It is hence desirable to use Biohybrid devices that employ synthetic semipermeable membranes to encapsulate islet cells and allow the use of alio or xeno origin cells. The membranes are expected to permi t the crossover of low molecular weight substances such as nutrient electrolytes, oxygen and bio-secretor products but not of transplant effectors. Polymeric membranes such as alginate-poly (L-lysine >, polycar¬bonate* polyvinyl chloride - acrrylic copolymers, poly (2-hydroxy ethyl methacrylate)5 agarose, polyvinyl alcohol have been

proposed as immunoisolation matrices. Such membranes have been used in various device configurations including microcapsules, AV shunts^ hoi low fibers and planar diffusion chambers• However, fibrotic react ions» biocompatibllity, mechanical fragility and reduced permeation have been reported to be the 1imiting -factors for the widespread use of these candidate materials* It is the basic requirement that the membrane materials should exhibit satisfactory biocompatibllity, ie. the ability of the material to induce minimal inflammatory response in the host's tissue resulting in acceptance of the implant without altering its function.
For a successful application of this technology, the ability to retrieve a material, which may not function to the best possible response, should also be possible. Degraded microcapsules of encapsulating membranes or non-functional islets that cannot be retrieved may pose a problem in the long term by inducing antigenic reactions.
OBJECTS OF THE INVENTION
It is therefore an object of this invention to propose a bio¬compatible polymeric composition which does not induce fibrotic reactions.
It is a further object of this invention to propose a bio¬compatible polymeric composition which is easily retrievable-

Another object of this invention to propose a bio-compatible polymeric composition which is effective for the treatment of diabetes without immunosuppression«
Yet another object of this invention to propose a bio-compatible polymeric composition for immunoisolating encapsulated ^ islet cells within the membranes and which permit the cells to be V1ab1e *
Other objects and advantages of the invention will be more apparent from the ensuing description•
BRIEF DESCRIPTION OF THE INVENTION
Thus according to this invention is provided a biocompatible
polymeric composition of an interpenetrating polymer network
comprising a biocompatible polyurethane and a biocompatible vinyl
polymer.
According to this invention is further provided a process for the
preparation of a biocompatible polymeric composition of an inter¬penetrating polymeric network of a biocompatible polyurethane in an organic solvent to form a
solut ion 9 f ol lowed by dissolving 1(?>""3^VJ of a vinyl monomer ^ an
initiator in a proportion of l"2y» by weight of the vinyl monomer
and a crosslinker in a proportion of 1-2% by weight of the vinyl
monomer in the solution to form a homogeneous mixture» followed
by curing the same to obtain the biocompatible polymeric
composition of an interpenetrating polymeric network
In accordance wi th this invention f a 70-90*/f solution of a bio-
compatible polyurethane is prepared by dissolving the poly-
urethane in a good solvent for it such as tetrahydrofuraoi
dimethyl formamide« dimethyl acetamide to form a homogeneous
solution? either at room temperature or by heating in the range
o of 60-70 C and stirringi if necessary. A monomer of the second
polymer is chosen from a group of either hydrophobic or hydro-philic vinyl monomers and a weight fraction of i0-Z0% of the same is dissolved in the same chosen solvent for the polyurethane and stirred together so as to form a homogeneous mixture. An initiator of the monomer of the second polymer is chosen from a group of either free radical or redox or other initiator for a vinyl monomer and a weight fraction of 1-2% of the second monomer concentration dissolved in the same chosen solvent for the poly¬urethane and stirred together so as to form a homogeneous mixture. Further» a crosslinker of the second polymer9 which may be another smal1 molecule with a vinyl group in it such as ethylene glycol dimethacrylate» N,N' bis acrylamide, etc. at a weight fraction of 1-254 of the second monomer concentration 9 is dissolved in the satne chosen solveTit for the polyurethane and
stirred together so as to form a homogeneous mixture * The mixture
a is allowed to cure together in a mold for 24-48 hours at 60-75 C.
The IPN is formed by comfain-ation of two polymers where the first
polymer is a polyurethane and the second polymer is a vinyl
polymer. The polyurethane is a 1inear segmented polyurethane

which has hard and soft segments with a polyol as the soft segment and a diol or diamine as the chain extender- The poly-* urethane may be either aliphatic or aromatic in nature.
The second polymer is a vinyl polymer which may be from a group which is either a hydrophilic or hydrophobic.
The second polymer may be from a group such as polyvinyl pyrrolidone, polymethyl methacrylate» polyacrylamide* poly-hydroxyethyl methacrylate and poly ethyl hexyl acrylate.
In accordance with an embodiment of this invention is provided
flat membrane sheets of the interpenetrating polymer network and
a method for the preparation of the same comprising dissolving
lj?i-50*/* by weight of the cured IPN in an organic solvent* such as
tetrahydrofuran, dimethyl formamide f dimethyl acetamide to form a
homogenous solution either at room temperature or by heating in
o the range of 60--*70 C and stirring, if necessary. The solution of
the IPN may have a concentration from 10-^0% of polymer in
solvent * The IPN solution is then cast in a mold as a flat
m&n±trane sheet. The IPN cast as sheet is then alloiij^d ttD contact
air for an hour. The partially cured membrane is then contacted
with ice cold water for 24 hrs. and later removed from mold and
o cured at 60 C in an oven and by immersing in water. This is
followed by extraction with solutions of hexane and ethanol-water
mixtures and distilled water to remove unreacted components from
the membrane.

In accordance with a further embodiment 9 the IPN solution is made into a porous tube by coating on a plastic mandrel once in the solution and withdrawing. The mandrel is then inverted and allowed to cure by contacting air for 1 hr-. It is then dipped in ice cold water for 15 mins. to form the first coat layer of IPN1 The first coat IPN mandrel is dipped in the IPN solution for the second time to form the second layer. The procedure is continued till multiple layers, for eg. five consecutive layers of IPN are obtained. After which the mandrel is left in ice cold water for 24 hrs. The, IPN coated as tube is removed from mandrel inside out to form the porous tube of the invention.
According to further embodiments9 cylinders or other shapes may be obtained.
The membrane is selectively permeable to cell nutrients, meta¬bolites and waste molecules of less than 60,000 molecular weight and impermeable to the higher molecular weight immunoglobulins of greater than 66,000 molecular weight. It has open interconnected pores of 5-10 micron size in diameter, with a majority of the pores being 5-micron size. The IPfi membranes of the invention are retrievable on implantation.
In accordance with a still further embodiment of this invention, IPN biohybrid islet implant and a method for implantation is
provided which reverses the diabetic state of mice models- The

isolated islet cells are suspended in a alginate gel, formed by mixing a solution of sodium alginate solution containing the islets with a calcium chloride solution, and the gel containing islets is introduced in an IPN porous tube of the invention or flat sheet membrane pouch of the invention. The IPN porous tube or flat sheet device of the invention containing the gel with islets is sealed with the IPN solution and pressure, or sealed by applying a hot seal and pressure. The biohybrid IPN-islet implant is implanted in the peritoneal cavity of diabetic mice and allowed to reverse the diabetic state of the mice*. The implantation of the biohybrid implant of the invention is not restricted to the peritoneal site but covers all other sites of implantation in animal or human bodies. Further, the IPN of the invention is not restricted to use with islet cells alone but also for any other cell type requiring immunoisolation prior to transplantation, eg. hepatocytes^ dopamine producing cells, chromaffin cells, etc.. The IPN of the invention is also not restricted to the permeation of molecules necessary for the treatment of diabetes, but also to the permeation of all mol Gcules within the range of upto 60,^00 molecular* weight and may relevant to the^ treatment of any type of disease that my require the use of immunoisolation techniques.
The invention will now be explained in greater detail with the
heIp of non-1imi ting examples.

Example 1:
A polymeric composition of an IPN material comprising an aliphatic polvurethane and a hvdrophilic vinvi polvmer( PU-PVP Semi IPN)
A1. Synthesis of the aliphatic linear segmented polyurethane
A molar concenteration of an aliphatic diisocyante such asHydrogenated methylene bisdiisocyanate (HMD!) is taken in a 3 necked flask or polymer reactor fitted with a stirrer and a condenser. A stoichiometric molar amount of the polyol, polytetramethylene ether glycol, is added dropwise to the stirred HMDI solution in an atmosphere of nitrogen. 0,2 wt% of a catalyst dissolved in a small amount of the solvent N,N, dimehtylacetamide was added to the reaction flask. Reaction is carried out at 60'C for an hour. Theteactant mixture consisting of a prepolymer is cooled and chain extended with addition of a chain extender such as butanediol with stirring* Stoichiometric quantities of the polyol, chain extender and diisocyanate are selected so as to have a final NC: OH ratio of 1.1 and is well known to those skilled in the art The temperature of the reactant mixture is raised to 60^C for an hour more and reactant mixture is transferred to a polyethylene mold in an oven, in the form of a thin film, for further curing of 48 hours at 60^C
B1, Synthesis of the aliphatic- hydrophic -PU-PVP Semi IPN : ( PU-PVP 10% SemlPU)
AID wt% solution of tt% poiyur^hane in solvent dlmethylacetamide, prepared by dissolving the polyurethane prepared as in (a) above in the solvent is mxed with
an amount of N- Vinyl pyrrolidone monomer, such that the final ration of polyurethane to vinyl monomer is 90:10, An Initiator for vinyl polymers such as azobisisobutyronitrHe (AIBN) at a conceftteration of 1 wt% o#^ vinyl mondfln^r, and crosslinker for vinyl polymers such as ethyteig^col dimethacrylate at a concenteration of 1-3% of the vinyl monomer is added to the iWxture. The entire mixtufd Is Introduced in the polyethylene niold and cured at 80°C for 2 hours and further 60°C for 24 hours In an oven.

Alternate procedure:
A2. Linear aliphatic segmented polyurethane
Any biocompatible grade linear segmented polyurethane of molecular weight of atleast > 60000 and known to be prepared from aliphatic diisocyanate, commercial samples like Tecoflex 60 D, Chronoflex etc are examples, is dissolved in a solvent such as N,N dimethyl acetamide at a concenteration ranging from 10-15 wt% to fomi the solution of polyurethane of the Semi IPN.
B2. Synthesis of the aliphatic-hydrophilic- PU-PVP Semi IPN : ( PU-PVP 10% Semi IPN)
A 10 wt% solution of the polyurethane such as Tecoflex 60 D in solvent dimethylacetamide, prepared by dissolving the polyurethane prepared as in (A2) above in the solvent is mixed with an amount of N- Vinyl pyrrolidone monomer, such that the final ration of polyurethane to vinyl monomer is 90:10. An initiator for vinyl polymers such as azoblsisobufyronitrile (AIBN) at a concenteration of 1 wt% of the vinyl monomer, and crosslinker for vinyl polymers such as ethylenglycol dimethacrylate at a concenteration of 1-3% of the vinyl monomer is added to the mixture. The entire mixture is introduced in the polyethylene mold and cured at 80°C for 2 hours and further 60°C for 24 hours in an oven.
Example 2:
Semi iPNs of an IPN material comprisino an aliphatic polvurethane and a hvdrophilic vinvl polvmer (PU-PVP Semi IPN) of 80:20 and 70: 30 compositions.
For Semi IPNs of polyurethane and N vinyl pyrrolidone of compositions 80:20 or 70:30, the concenterations of the aliphatic polyurethane as in A1 or A2 of example 1 above, is 80 wt% and 70 wt% respectively, and the amount of vinyl monomer added is 20 wt% and 30 wt% respectively. An initiator for vinyl polymers such as azot)isisobutyronitrtle (AIBN) at a concenteration of 1 wt% of the vinyl monomer, arwl crosslinker for vinyl polymers such as ethylenglycol dimethacrylate at a concenteration of 1-3% ofthe vinyl monomer is added to the rriixture. The entire mixture is introduced in the polyethylene mold and cured at SO^C for 2 hours and further 60°C for 24 hours in an oven.
Example 3:

Semi IPNs of an IPN material comprising an aliphatic polvurethane and a hvdrophilic vinvl polvmer such as polvacrvlamide( RAM) or hvdroxvethvl methacrvlate (PHEMA).
For Semi IPNs of polyurethane and polyacrylamide (PAM) of compositions, 90:10; 80:20; 70:30, the concenterations of the aliphatic polyurethane as in A1 or A2 of Examp.le 1 above is 90 wt%; 80 wt% and 70 wt% respectively, and the amount of vinyl monomer such as acrylamlde, hydroxyethyl methacrylate added is 10 wt%; 20 wt% and 30 wt% respectively. An initiator for vinyl polymers such as azoblslsobutyronitrile (AIBN) at a concenteration of 1 wt% of the vinyl monomer, and crosslinker for vinyl polymers such as ethylenglycol dimethacrylate at a concenteration of 1-3% of the vinyl monomer is added to the mixture. The entire mixture is introduced in the polyethylene mold and cured at BO'C for 2 hours and further 60°C for 24 hours in an oven.
Example 4:
Semi IPNs of an IPN nriaterial comprising an aliphatic polvurethane and a hydrophobic vinvl polvmer such as polvmethvl methacrvlate (PMMA) or polveth vlhexvlacrvlate. PEHA.
For Semi IPNs of polyurethane and hydrophobic vinyl monomers of polymethylmethacrylate or polyethyl hexyl acrylate of compositions, 90:10; 80:20; 70:30, the concenterations of the aliphatic polyurethane as in At or A2 of Example 1 above is 90 wt%; 80 wt% and 70 wt% respectively, and the amount of vinyl nrxinomer such as methyl methacrylate or ethyl hexyl acrylate added is 10 wt%; 20 wt% and 30 wt% respectively. An initiator for vinyl polymers such as azobisisobutyronitrile (A16N) at a concenteration of 1 wt% of the vinyl monomer, and crosslinker for vinyl polymers such as ethylenglycol dinoethacrylate at a concenteration of 1-3% of the vinyl monomer is added to the mixture. The entire mixture is introduced in the polyethylene mold and cured at 80**C for 2 hours and further SO^C for 24 hours in an oven.
ExaiBfifo SI
A polvmeric composition of an IPN material comprising an aron^atic polvurethane and a hvdrophilic vinvl polvmer( PU-PVP Semi IPN)
A3. Svnthesis of an aromatic polvurethane
3 moles of toluene diisocyanate was converted to a biuret by adding stoichiometric amount of water in a 3 necked flask fitted with a stirrer and a condenser or polymer reactor in nitrogen atmosphere. The mixture was hated using 0.1 wt % of a catalyst, dibutyltindialaurate for 30 minutes. The white

mass of biuret formed was cooled and dissolved in dimethylacetamide as the solvent. A stopichiometeric anwunt of polyol was added to the clear liquid abnd the reaction was carried out for an hour with heating. The contents were cooled to room temperature and the crosslinker such as trimethylol propane was added with vigorous stirring. The mixture was degassed and poured on to a polyethylene mold and cured at 80°C for 2 hours and further 60°C for 24 hours in an oven.
B 3. Synthesis of the aromatic - hvdroDhilic (PU-PVP Semi IPN): (PU-PVP10%SemilPN)
A 10 wt% solution of the polyurethane in solvent dimethylacetamide, prepared by dissolving the polyurethane prepared as in (A3) above in the solvent is mixed with
an amount of N- Vinyl pyrrolidone monomer, such that the final ration of polyurethane to vinyl monomer is 90:10. An initiator for vinyl polymers such as azobisisobutyronitrile (AIBN) at a concenteration of 1 wt% of the vinyl monomer, and crosslinker for vinyl polymers such as ethylenglycol dimethacrylate at a concenteration of 1-3% of the vinyl monomer is added to the mixture. The entire mixture is introduced in the polyethylene mold and cured at 80°C for 2 hours and further 60°C for 24 hours in an oven.
Alternate procedure:
A5. Linear aromatic segmented polyurethane
Any biocompatible grade linear segmented polyurethane of molecular weight of atleast > 60000 and known to be prepared from aromatic dlisocyanate, commercial samples like Biomer are examples, is dissolved in a solvent such as N.N dimethyl acetamide at a concenteration ranging from 10-15 wt% to form the solution of polyurethane of the Semi IPN;
B5. Synthesis of the aromatic-hydrophilic- PU-PVP Semi IPN : ( PU-PVP 10% Semi IPN)
A 10 wt% solution of the polyurethane in solvent dimethylac^amide, prepared by dissolving the polyurethane prepared as in (A5) above in the solvent is mixed with
an amount of N- Vinyl pyrrolidone monomer, such that the final ration of polyurethane to vinyl monomer is 90:10. An initiator for vinyl polymers such as azobisisobutyronitrile (AIBN) at a concenteration of 1 wt% of the vinyl monomer, and crosslinker for vinyl polymers such as ethylenglycol dimettiacrylate at a concenteration of 1 -3% of the vinyl monomer is added to the mixture. The entire mixture is introduced in the polyethylene mold and cured at 80°C for 2 hours and further 60°C for 24 hours in an oven.
Example 6:

Preparation of a flat membrane bv phase inversion process
An IPN prepared by any of the examples above or by other methods known to those skilled in the art is extracted with polar and non polar solvents to remove any unwanted reaction products, mold releasing agents, impurities etc and dried before redissolving in a suitable good solvent such as dimethylacetamide, dimethylformamide etc, at a concentration ranging from 10-20 wt % dependent on the molecular weight of the pdyurethane so as to form a viscous solution. The solution is cast on a flat polyethylene mold in the form of a thin film and allowed to contact air for and hour. The partially cured membrane is next contacted with a nonsolvent such as Ice cold water for 24 hours and removed from the mold. The flat membrane is immersed in a bath of water at 60oC for 5 hours before extensive washing in water and and further use.
Example 7:
Preparation of a tubular macrocapsule of an aliphatic polvurethane and hvdrophilic polvmer such as PU-PVP 20 wt% IPN bv phase inversion process.
A semi IPN formed from an aliphatic polyurethane as in example 1- B2 above is dissolved in the appropriate solvent at a concenteration ranging from 10-20 wt% and giving a viscous solution. A mandrel of a hydrophobic polymer such as Teflon, polyethylene glycol or polypropylene of outer diameter equivalent to the inner diameter of the required macrocapsule is dipped in the viscous solution of the polyurethane. The mandrel is removed from the solution and contacted with air in an inverted position for a time period ranging from 15 minutes to an hour. The coated mandrel is then immersed in ice cold water for a time period ranging from 15 minutes to an hour. Upto 5 alternate coats of IPN solution and water are done this way. Following the last coat of polymer and water, the thin tubular film of the IPN formed on the mandrel is manually removed and turned inside out and immersed in a container containing water at 0-10 ^C, for 24 hours. The tubes are finally extracted with water in several washes before actual use to encapsulate islet cells.
Example 8:
Encapsulation of islet cells in PU-PVP macrocapsules for treatment of diabetes in animal models.
A6. Isolation of pancreatic islet cells from mice
BALB/c mice of 10 weeks were sacrificed by cervk:al dislocatkni, pancreas dissected, minced and incubated in 1 mg/ml collagenase P (Boehringer Mannheim, Germany) on a shaker platform for 20 minutes. Freshly isolated islets were then cultured in RPM11640 (GibcoBRL, NY, USA) medium with 10% FCS

for 48 h. Islets (n=30) were handpicked and cultured on membranes (1 cm^) in 24 well plate (Nunclon. Denmark) and their morphology observed under phase contrast microscope for 5 days. Viability of islets cultured on membranes was detennined by trypan blue dye exclusion test, using 0.04 % (vwV) trypan blue. Islets staining blue were scored dead while viable islets were those that did not take up the dye.
B6 . Encapsulation of mice pancreatic islet cells in PU-PVP macrocapsules
Viable islets of (1 IE == 150 ^m diameter islet) were handpicked and washed with Hanks buffer. Islets were suspended in a solution of 2 wt % sodium alginate such that a total concenteration of 500 IE of islets could be introduced through the open end, in each tubular macrocapsule formed from a PU-PVP IPN ( prepared earlier as per example 7 above), of dimensions 3.8mm inner diameter, and enclosing a volume of 200 pi, by addition of 150 pi of the alginate-islet suspension and having one open end. A small amount of calcium chloride solution may or may not be added to increase the viscosity of the alginate gel and prevent free flow of the suspension of islets from the macrocapsule. The open end of the macrocapsule was then sealed with a heat seal and edges of the seal rounded by immersion of the portion of the seal in a solution of the same IPN composition and immediately washing in Hanks buffer. The macrocapsules containing islet cells were stored in Hanks solution before surgery for transplantation was started on the animal models.
Example 9:
In vivo biohvbrid pancreas transplantation studies
Streptozotocine induced diabetic mice were used for the transplantation and monitoring of diabetic status in animal experiments. Animals were fasted overnight and anaesthetized by /.p. administration of thiopental sodium at a dose of 40 mg/kg body weight. A small incision is made in peritoneum and two tubular grafts containing 500 IE (1 IE = 150 ^m diameter islet) each, suspended in 1% alginate gel matrix, were implanted while diabetic control animals received empty tubular grafts. Inct^>ns were sutured using absorbable 6-0 catgut sutures and autoclipper (Becton Dickinson, USA). All animals received an i-p injection of gentamycin (3 nr^g b.w.), ampicittin and ckDxacillin (20 mg/kg b.w.) and diclofenac sodium (0.5 mg/kg b,w.), for 3 days (starting from the operattve day) in addition to the topical ointments (Soframycin). Animals were followed for 14 post-operative weeks with weekly non-fasting blood glucose measurements using glucose oxidase kit (Sigma, USA). On 12^ week post-transplantation, some of the tubuter grafte (n=4) were retrieved to confirm islet graft functloa All animals v^re also subjected to intra peritoneal glucose tolerance test (2.0 g/kg b.w.) at the end of 12*^ week post transplantation. The study was carried out in 12 animals and compared to a similar number of control normal mice glucose levels during the sanr^ period. The glucose levels in the diabetic mice which were initially highly elevated couM be brought down to normal levels within 48

hours of implantation of the encapsulated islet macrocapsules. The normal glycemic levels were maintained throughout the period of the study confirming the utility of the system to cure diabetes in a diabetic animal model. No immunesuppressing drugs to avoid the rejection of the transplanted islets was used in this study and the macrocapsule is believed to have selectively perfomed as a barrier for the transfer of Immunoglobulins, cytokines, macrophages and other cells of the host animal that can cause rejection of the transplanted islets.

WE CLAIMS
1. A process for the preparation of a biocompatible polymeric composition of an inter-penetrating polymeric network 2. The process as claimed in claim 1 wherein said vinyl polymer
is selected from hydrophi1ic and hydrophobic vinyl monomers-
3. The process as claimed in claim I wherein said polyurethane is an aromatic or a aliphatic polyurethane.
4. The process as claimed in claim 3 wherein said polyurethane is a linear segmented polyurethane with hard and soft segments.
5. The process as claimed in claim 4 wherein said polyurethane
comprises a polo as the soft segment and a compound selected
from a idol and dopamine as the chain extender,
6. The process as claimed in claim 1 wavering said initiator is»
such as a free radical 9 redo or any other initiator suitable for
vinyl monomers.
7- The process as claimed in claim 1 wherein said cross linker is a molecule with a vinyl group« such as ethylene glycol dimeth-acrylate, N,N'-bisacrylamide.

8. The process as claimed in claim 1 wherein said solvent is an
organic solvent« such as tetrahydrofuran, diethyl form amide,
diethyl ace amide.
9. The process as claimed in claim 1 wherein said polyurethane is
dissolved in the solvent to form a homogeneous solution at room
o temperature or by heating at 60-70 C with stirring, if required.
10. The process as claimed in claim 1 wherein curing is effected
temperature in the range of 60-75 C.
11. The process as claimed in claim 1 wherein curing is done for
a period of 24-48 hrs..

12. The process as claimed in claim 1 wherein curing is done in a mold •
13. A biocompatible polymeric composition of an inter-penetrating polymer network comprising a biocompatible polyurethane and a biocompatible vinyl polymer.
14. The composition as claimed in claim 13 wherein said vinyl
polymer is selected from a group of polymers, such as polyvinyl
pyrro-1idone polymethyl methaerylate, polyacrylamide, poly-
late and poly-ethyl-hexylacrylate .
15. The composition as claimed in claim 13 wherein the proportion
of said polyurethane is 70-90*/* and the proportion of the vinyl
polymer is 10--30% by weight.
16. The composition as claimed in claim 13 wherein said vinyl
polymer is selected from and hydrophobic vinyl
monomers.

17. The composition as claimed in claim 13 wherein said
polyurethane is an aromatic or a aliphatic polyurethane .
18. The composition as claimed in claim 17 wherein said polyurethane is a linear segmented polyurethane with hard and soft segments,
19. The composition as claimed in claim 18 wherein said polyurethane comprises a polyol as the soft segment and a compound selected from a dial and diamante as the chain extender. 20- A process for the preparation of IPN membranes comprising dissolving 10-50% of the composition of the inter-penetrating polymer network in a solvent and casting the same in a mold as a flat membrane 9 contacting the same with water, followed by removing from the mold» curing the sheet and extracting unseated components from the membrane to obtain IPN membranes.
211, The process as claimed in claim 20 wherein said solvent is selected from tetrahydrofuran, dimethyl formamide, dimethyl acetamide.
22. The process as claimed in claim 20 wherein said composition
o of IPN is dissolved at room temperature or by heating at 60-70 C
with stirring? if required.
23. The process as claimed in claim 20 wherein the unrelated
components are removed by extraction with solutions of hexane 9
ethanol-water mixtures and distilled water.
24. An IPN membrane for immune-isolating living cells.
25. A process for the preparation of IPN porous tube comprising

dissolving of an IPN composition in a solvent to form a
solution* cationic the isolation on a mandrel followed by inverting
the mandrel, curing, dipping in water to form the first IPN
layer,
repeating the process to form multiple layers, dipping the
mandrel and removing the IPN porous tube from the mandrel.
26P The process as claimed in claim 25 wherein curing is effected
o at 60-70 C.
27. An IPN porous tube for immune-isolating living cells.
28. A process for producing an IPN biohybrid islet implant
comprising suspending isolated islet cells in an alginate gel
followed by mixing a calcium chloride solution thereto and intro¬
dicing the gel with the islet cells into an IPN tube or pouch
made from IPN membrane, sealing the tube or pouch.
29*, The process as claimed in claim 28 wherein the pouch or tube
containing the islet cells are sealed with IPN solution and
pressure or by applying a hot seal and pressure.
30. The process as claimed in claim 28 wherein said biohybrid
IPN-islet implant is implanted in the peritoneal cavity of
diabetic mice and allowed to reverse the diabetic state of the
mice.
31 • A biohybrid IPN islet implant for reversal of the diabetic
state of mice.

Documents:

« Previous Patent

Next Patent »

Patent Number

230740

Indian Patent Application Number

47/MAS/2002

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

27-Feb-2009

Date of Filing

21-Jan-2002

Name of Patentee

SREE CHITRA TIRUNAL INSTITUTE FOR MEDICAL SCIENCES & TECHNOLOGY

Applicant Address

BIOMEDICAL TECHNOLOGY WING, POOJAPPURA, THIRUVANANTHAPURAM 695 012,

Inventors:

#	Inventor's Name	Inventor's Address
1	NAIR PRABAHA DAMODARAN	C/O SREE CHITRA TURUNAL INSTITUTE FOR MEDICAL SCIENCES & TECHNOLOGY, AN INDIAN INSTITUTE OF BIOMEDICAL TECHNOLOGY WING, POOJAPPURA, THIRUVANANTHAPURAM 695 012,

PCT International Classification Number

A61M 31/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA