Photopatterned surfaces for site-specific and functional immobilization of proteins

Photosensitive silanes containing nitroveratryl (Nvoc)-caged amine groups and protein repellent tetraethylene glycol units were synthesized and used for modification of silica surfaces. Functional surface layers containing different densities of caged amine groups were prepared and activated by UV-irradiation of the surface. The performance of these layers for functional and site-selective immobilization of proteins was tested. For this purpose, biotin and tris-nitrilotriacetic acid (tris-NTA) were fist coupled to the activated surface, and the interaction of streptavidin and His-tagged proteins with the functionalized surfaces was monitored by real-time label-free detection. After optimizing the coupling protocols, highly selective functionalization of the deprotected amine groups was possible. Furthermore, the degree of functionalization (and therefore the amount of immobilized protein) was controlled by diluting the surface concentration of the amine-functionalized silane with a nonreactive (OMe-terminated) tetraethylene glycol silane. Immobilized proteins were highly functional on these surfaces, as demonstrated by protein-protein interaction assays with the type I interferon receptor. Protein micropatterns were successfully generated after masked irradiation and functionalization of the caged surface following the optimized coupling protocols.