DEGRADATION AND RELEASE BEHAVIOR OF DEXTRAN-BASED HYDROGELS

Dextran hydrogels were prepared by radical polymerization of aqueous s olutions of glycidyl methacrylate-derivatized dextran (dex-MA), hydrox yethyl methacrylate-derivatized dextran (dex-HEMA), and HEMA-oligolact ate-derivatized dextran (dex-lactateHEMA), using potassium peroxydisul fate and N,N,N',N'-tetramethylethylenediamine (TEMED) as the initiatin g system. Dex-MA hydrogels only degraded under extreme conditions (100 degrees C, pH 1-3), whereas hydrogels derived from dex-HEMA or dex-la ctateHEMA degraded fully at pH 7.2 and 37 degrees C, due to hydrolysis of the lactate and/or carbonate esters in the cross-links. The degrad ation time of these gels can be tailored from 2 days to more than 2 mo nths by varying the nature of the spacer, the degree of substitution(1 ) of dextran (DS), and the initial water content of the hydrogels. The release kinetics of a model protein, Immunoglobulin G, from dex(lacta te)HEMA hydrogels were investigated and shown to be dependent on both the DS and the initial water content of the gel. Under certain conditi ons zero-order release was observed over a period of 10 days.