Synthesis of a new PHEMA/PEO enzymatically biodegradable hydrogel

We report the synthesis of a new enzymatically degradable gel based on PHEMA and PEO crosslinking macromonomer. The crosslinker contains the tripeptide sequence Gly-Gly-Leu, which is a substrate for proteases such as subtilisin or chymotrypsin. The crosslinker was obtained by the coupling reaction of succinyl-glycyl-glycylleucine with 2-aminoethyl-terminated PEO chains ((M) over bar (W) = 3 400) and subsequent esterification of the hydroxyl end-group with methacryloyl chloride. It was characterized by SEC and H-1 NMR. Enzymatic cleavage of the crosslinking macromonomer was showed by SEC. The macromonomer was copolymerized with HEMA to yield hydrogel that is stable in a physiological buffer. Enzymatic assay showed that this gel is degraded in the presence of a bacterial protease (subtilisin). The degradation is complete within 50 d at 37 degrees C. This new gel is a good candidate for drug-delivery systems where the release can be triggered by the presence of bacterial proteases.