Control of cell adhesion on poly(ethylene glycol) hydrogel surfaces using photochemical modification and micropatterning techniques

Cell and protein-repellent poly(ethylene glycol) (PEG) hydrogels surfaces were modified to covalently attach cell adhesion proteins and subsequently promote cell adhesion. Collagen was chosen as a cell adhesion protein and covalently immobilized to the hydrogel surface via a 5-azidonitrobenzoyloxy N-hydroxysuccinimide (NHS), bifunctional linker, which has a phenyl azide group and a protein-binding NHS group on either end. Using the photochemistry of phenyl azide groups, the bifunctional linker was chemically fixed to the hydrogel surface by UV exposure and the N-hydroxysuccinimide groups were allowed to react with the free amine groups of collagen. The immobilization of collagen on the PEG hydrogel surface was demonstrated with XPS by confirming the formation of a new nitrogen peak and the resulting amount of immobilized collagen was dependent on the concentration of bifunctional linker. Cell adhesion studies revealed that collagen immobilization resulted in a significant improvement of cell adhesion and spreading on the PEG hydrogel substrates. Photochemical fixation combined with photolithography produced well-defined collagen micropatterns on the PEG hydrogels and cells adhered only on the collagen-modified region due to the lack of adhesion for proteins and cells to PEG.