Comparative studies of surface topography and mechanical properties of a new, photo-switchable PEG-based hydrogel

Abstract

We have recently synthesized a novel nitrocinnamate-modified poly(ethylene glycol) hydrogel, further referred to as PEG–NC hydrogel, via photo-crosslinking of the nitrocinnamoyl groups. The practical advantage of photo-gelation is that it allows facile control of the gelation process and thereby properties of formed hydrogel in situ. In this paper, we present an investigation of the physico-chemical properties of the photo-sensitive PEG–NC hydrogel. Using environmental scanning electron microscopy (ESEM) and atomic force scans (AFM force scans) techniques, we explored the changes in surface topography and mechanical properties of this new photo-switchable hydrogel in its different stages, i.e. photo-crosslinked and photo-cleaved, and a hydrogel created by crosslinking of the previously photo-cleaved one. We have observed distinct differences in both the surface topography and the mechanical properties between the photo-crosslinked and photo-cleaved stages of the hydrogel, and have demonstrated this to be a reversible process. NMR experiments were also carried out to illustrate the photochemical process. We believe that this novel, potentially biocompatible hydrogel could have biomedical applications, especially in the areas of wound healing, surgical implants, tissue engineering and artificial muscles.