Synthesis of photoresponsive hybrid alginate hydrogel with photo-controlled release behavior

A photoresponsive hybrid alginate hydrogel was successfully prepared by Ca2+-mediated crosslinking reaction with a mixture of beta-cyclodextrin-grafted alginate (beta-CD-Alg) and diazobenzene-modified poly(ethylene glycol) (Az(2)-PEG). The water-soluble Az(2)-PEG exhibits efficient trans-to-cis isomerization of the terminal azobenzene moieties under UV-light irradiation and readily switched back to the initial trans state under visible light. Because of low affinity between beta-CD and cis-Az, the host-guest inclusion complex formed by beta-CD and trans-Az gradually dissociates under UV-light exposure. Accordingly, the bulk gel exhibits substantial photo-induced transformation in gel morphology by the appearance of significant comb-like cavities. This photosensitive behavior accompanied by the structural degradation enables the rapid release of entrapped dye molecules under UV light stimulus. Moreover, an incident light with higher power and mild acidic environment are capable of accelerating the photo-triggered release, thus allowing the potential applications toward acute wound healing. (C) 2014 Elsevier Ltd. All rights reserved.