Thermoresponsive degradable hydrogels with renewable surfaces for protein removal.

Most biological materials used in the body undergo protein adsorption, which alters their biological functions. Previously, we introduced surface-degradable hydrogels as adsorbed protein-removing surfaces. However, only a few surface renewals were possible because of the hydrophilic nature of the hydrogels, which accelerated their degradation. In this research, we introduced thermoresponsive properties of hydrogels for limited degradation for protein removal. Hydrogels were synthesized by the radical polymerization of N-isopropylacrylamide (NIPAAm), 2-methylene-1,3-dioxepane, and poly(ethylene glycol) monomethacrylate (PEGMA). The synthesized hydrogels demonstrated thermoresponsive behavior derived from poly(NIPAAm). At 10 °C, the hydrogels swelled and exhibited bulk degradation. After 2 h, the prepared hydrogels were degraded completely. However, at 37 °C, the hydrogels shrunk and showed surface degradation. After 7 h of degradation, the swelling ratio of the hydrogels changed marginally. The proteins adsorbed on the hydrogel surfaces were removed via surface degradation. However, the fluorescence intensity of adsorbed proteins increased on the hydrogel surfaces without degradable functions. In addition, the fluorescence intensity of adsorbed proteins increased in the hydrogels without PEG graft chains, suggesting that the prepared thermoresponsive hydrogels with PEG chains could be used as potential biomaterial surface coating materials, exhibiting regenerative low-fouling ability.