PEG-based hydrogel synthesis via the photodimerization of anthracene groups

Photo-cross-linking has received a considerable attention for the design of intelligent materials in biochemical and biomedical applications. In this report, we describe the synthesis and properties of a novel photoreversible poly(ethylene glycol)- (PEG-) based hydrogel system. 9-Anthracenecarboxylic acid was used to modify the hydroxyl groups of an eight-armed PEG polymer (molecular weight 20 000) and the degree of substitution was determined to be 87.4%. The PEG-anthracene macromers (PEG-AN) exhibited high photosensitivity at wavelengths close to visible light (absorption maxima at 366 and 380 nm) and underwent rapid and reversible photo-cross-linking upon exposure to alternating wavelengths of irradiation (365/254 nm) in the absence of photoinitiators or catalysts. Changes in light exposure and wavelength of irradiation reversibly altered the physicochemical properties of the PEG-AN hydrogel, including swellability, absorption spectrum, and topography.