HYDROLYTIC AND ENZYMATIC DEGRADATION OF POLY(GAMMA-GLUTAMIC ACID) HYDROGELS AND THEIR APPLICATION IN SLOW-RELEASE SYSTEMS FOR PROTEINS

The hydrolytic and enzymatic degradation of newly developed hydrogels, produced by crosslinking purified poly(gamma-glutamic acid) (gamma PG A) with dihaloalkane compounds, was studied and is reported in this pa per. Analysis of hydrolysis of the hydrogel as a function of pH indica ted that the hydrolysis occurred slowly at neutral pH, but fast in bot h acidic and alkaline solutions, while the polymer could be hydrolyzed rapidly only in acidic solutions. The ester bonds were more sensitive to hydrolysis than peptide bonds. The biodegradability of the hydroge l and polymer was further confirmed when enzymatic degradation was stu died by three enzymes (cathepsin B, pronase E, and trypsin), which wer e able to cleave both ester and peptide bonds gradually. A slow-releas e system for porcine somatotropin (pST) formed by using the hydrogel a s matrix to entrap the hormone was evaluated in vitro and in vivo. Res ults demonstrated that the hydrogel was able to release the hormone fo r a period of 20-30 days and indicated its potential application in sl ow-release systems for bioactive materials, especially macromolecules, such as peptides and proteins.