The Effect Of Ultraviolet Light On Biorepulsive Hydrogel Poly(Ethylene Glycol) Films

We studied the effect of ultraviolet (UV) light (254 nm) on porous poly(ethylene glycol) (PEG) films, formed by cross-linking of the epoxide- and amino-terminated four-arm STAR-PEG compounds. The major effect of irradiation is progressive decomposition of the PEG material followed by immediate desorption of the released fragments. The removal of the PEG material can be coarsely described by zero-order kinetics with a rate constant of 0.32 +/- 0.05 nm/(J/cm(2)). Surprisingly, this process does not affect the chemical composition of the residual film, which preserves all the useful properties of the original PEG material, including its hydrogel character and biorepulsion behavior, which is in striking contrast to the effect of electron irradiation on the PEG films and the effect of UV irradiation on oligo(ethylene glycol) (OEG)-substituted self-assembled monolayers, for which the removal of the PEG/OEG material is accompanied by substantial chemical modification of the residual part, losing its original properties. The behavior of the PEG films under UV irradiation is not only an interesting and unexpected phenomenon but can also be applied to three-dimensional patterning of PEG materials, with the preservation of biorepulsive properties over the entire patterns, which can be potentially useful for applications.