Dextran based photodegradable hydrogels formed via a Michael addition

A photodegradable, covalently crosslinked hydrogel system has been constructed from the biocompatible polymers dextran and poly(ethylene glycol) using the acrylate-thiol Michael addition as the crosslinking method. Light sensitivity of the hydrogel was introduced by placing a non-toxic photolabile o-nitrobenzyl moiety in between dextran backbone and acrylate group. Hydrogels were prepared under physiological conditions without the need of any additional reagents by mixing solutions of dextran functionalized with acrylate-modified o-nitrobenzyl moieties (Dex-AN) and dithiolated poly(ethylene glycol) (DSPEG). The degradation of the hydrogels due to UV irradiation was investigated with scanning electron microscopy, infrared and UV-vis spectroscopy. Using green fluorescent protein (GFP) as a model protein, light triggered protein release from the obtained gel matrices was investigated in different forms. Furthermore, photodegradation of the hydrogel via two photon excitation was also examined using focused pulsed near infrared (NIR) laser beam as a light source.