Structure-property relationships in poly(ethylene glycol)-protein hydrogel systems made from various proteins.

A series of poly(ethylene glycol)-protein hydrogels were synthesized with different proteins, and the resultant structures were characterized in terms of swelling behavior and mechanical, optical, and drug release properties. Irrespectively of the protein involved in polymerization with poly(ethylene glycol), all studied systems were found to be loosely cross-linked networks, where both polymer and protein are completely solvated, enabling as high as 96% water content. Changes in the apparent transparency of the hydrogels synthesized with different proteins were attributed to the ability of the protein component to self-associate via hydrophobic interactions. The polyelectrolyte nature of the protein component governs the pH responsiveness of the network, which manifested itself in a pH-dependent mechanism of swelling and drug release. It was demonstrated that there is great opportunity to modulate the final characteristics of the hydrogel system to fit the need of specific biomedical application.