Stereocomplex hydrogels

Abstract

The invention relates to hydrogel compositions, which can be applied as biodegradable materials and to the processes to prepare such hydrogels. The hydrogel of the present invention comprises a stereocomplex gel structure which is the result of the interaction of oligomerized monomers of one chirality with that of oligomerized monomers of the opposite chirality, both grafted to hydrophilic polymers. The grafts form an interaction which is different from a covalent chemical interaction and thus provide the gel with the required coherence.

1 . A hydrogel composition comprised of a mixture of
 (A) a water soluble or water dispersible hydrophilic polymer grafted with oligomers or co-oligomers, wherein the oligomers or co-oligomers comprise homo-oligomers of L-lactic acid, and   (B) a water soluble or water dispersible hydrophilic polymer grafted with oligomers or co-oligomers, wherein the oligomers or co-oligomers comprise homo-oligomers of D-lactic acid,   in an aqueous system,   wherein said homo-oligomers of L-lactic acid and said homo-oligomers of D-lactic acid are comprised of 7-25 lactic acid monomers on average, and   wherein said homo-oligomers of L-lactic acid and said homo-oligomers of D-lactic acid interact noncovalently.   
     
     
         2 . The hydrogel composition of  claim 1 , wherein the water soluble or water dispersible hydrophilic polymer (A) is grafted with homo-oligomers of L-lactic acid, and the water soluble or water dispersible hydrophilic polymer (B) is grafted with homo-oligomers of D-lactic acid. 
     
     
         3 . The hydrogel composition according to  claim 1 , wherein the water soluble or water dispersible hydrophilic polymer is selected from the group consisting of dextran, starch, cellulose derivatives, albumin, lysozyme, poly(aminoacids), poly(lysine) and related copolymers, poly(glutamic acid) and related copolymers, poly (meth)acrylates, poly(meth)acrylamides, poly(vinylalcohol), poly(ethylene glycol), water soluble polyphosphazenes, and mixtures thereof. 
     
     
         4 . The hydrogel composition of  claim 1 , wherein the water soluble or water dispersible hydrophilic polymer is dextran. 
     
     
         5 . The hydrogel composition of  claim 1 , wherein the average degree of substitution is from 3-25. 
     
     
         6 . The hydrogel composition of  claim 1 , wherein the hydrogel is formed in microspheres. 
     
     
         7 . The hydrogel composition according to  claim 1 , further comprising an active ingredient. 
     
     
         8 . The hydrogel composition according to  claim 7 , wherein the active ingredient is a drug to be released. 
     
     
         9 . A process for the preparation of a hydrogel comprising:
 a) polymerizing L-lactic acid, optionally in the presence of a suitable initiator;   b) polymerizing D-lactic acid, optionally in the presence of a suitable initiator;   c) reacting the product of step a) with a suitable coupling compound and a water soluble or water dispersible hydrophilic polymer to form a water soluble or water dispersible hydrophilic polymer grafted with oligomers or co-oligomers, wherein the oligomers or co-oligomers comprise homo-oligomers of L-lactic acid;   d) reacting the product of step b) with a suitable coupling compound and a water soluble or water dispersible hydrophilic polymer to form a water soluble or water dispersible hydrophilic polymer grafted with oligomers or co-oligomers, wherein the oligomers or co-oligomers comprise homo-oligomers of D-lactic acid; and   e) mixing the product of step c) and the product of step d) in an aqueous system such that the homo-oligomers of L-lactic acid and the homo-oligomers of D-lactic acid interact noncovalently.   
     
     
         10 . The process of  claim 9 , wherein said suitable initiator comprises a primary or secondary hydroxyl group. 
     
     
         11 . The process of  claim 9 , wherein an active ingredient is added prior to or during step e). 
     
     
         12 . The process of  claim 11 , wherein the active ingredient is a drug to be released. 
     
     
         13 . The process of  claim 12 , wherein the drug to be released is selected from proteins and proteinaceous products. 
     
     
         14 . A method for drug delivery comprising administering the hydrogel composition of  claim 1 .