(510as) Surface Micropatterning of Poly(Ethylene Glycol) Hydrogel Using Surface Graft Polymerization Combined with Photolithography

This study presents the simple method to create protein micropattern on the poly(ethylene glycol) hydrogels through the surface-initiated graft polymerization and photolithography. The modification of the protein-repellent PEG hydrogel surface was achieved by two-step process including immobilization of benzophenone on the PEG hydrogel as surface initiator and subsequent surface-initiated polymerization of acrylic acid by UV irradiation. Surface modification of PEG hydrogels was demonstrated with FTIR/ATR spectroscopy and XPS by confirming the presence of carboxyl groups in the poly(acrylic acid). The use of designed photomask with photograft polymerization produced well-defined, pH-responsive PAA micropatterns with diameter ranging from 50 to 300 µm on the PEG hydrogels. The size of PAA micropatterns could be controlled by changing the environmental pH and 17 µm thick PAA micropattern at pH 4 became swollen to 80 µm thick at pH 7. Activation of carboxyl groups in PAA to covalently bind protein molecules made it possible to selectively immobilize proteins only onto the PAA micropattern in PEG hydrogel substrates due to the nonadhesivity of PEG. Based on these results, biotin was micropatterned on the PEG hydrogels and binding of streptavidin with micropatterned biotin was successfully investigated both qualitatively and quantitatively, demonstrating the possibility of micropatterned PEG hydrogels for the various biosensor systems.