Chymotrypsin responsive hydrogel: Application of a disulfide exchange protocol for the preparation of methacrylamide containing peptides

Methacrylamide groups were selectively coupled to cysteine residues in the presence of amines and alcohols by utilizing a disulfide exchange reaction in aqueous, acidic buffer. The tetrapeptide sequence, CYKC, was used as a cross-linker to create poly(acrylamide) hydrogels that dissolved when subjected to either a flowing or stationary solution of a-chymotrypsin. Control hydrogels that were cross-linked with the tetrapeptide, CSKC, were not affected by the same protease solution. In contrast, dissolution of both the CYKC and CSKC cross-linked hydrogel structures was accomplished by using the disulfide reducing agent tris(2-carboxyethyl) phosphine (TCEP). The chemoselective conjugation technique described could have utility for more advanced protease-responsive hydrogels as well as other hybrid materials composed of synthetic and biomacromolecules.