Selective immobilization of biomolecules onto an activated polymeric adlayer

The authors report a facile method for the selective immobilization of biomolecules onto a gold surface that was preactivated by a polymeric adlayer. The polymeric adlayer was designed to perform triple functions: high resistance to nonspecific protein adsorption, efficient surface anchoring, and subsequent covalent attachment of biomolecules. For this purpose, a random copolymer, poly(PEGMA-r-NAS), was synthesized by radical polymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA) and N-acryloxysuccinimide (NAS). In the first step, the polymeric adlayer was formed onto amine-terminated self-assembled monolayers (SAMs) on gold through covalent bond formation between reactive N-hydroxysuccinimide (NHS) ester of the copolymer and the amine of the SAMs. In the second step, amine-bearing biotin as a model biomolecule was covalently attached onto the polymeric adlayer that still contained unreacted NHS esters. The degrees of the binding sensitivity for a target protein and the nonspecific binding for four model proteins on the biotinylated polymeric adlayer were examined by surface plasmon resonance spectroscopy. Finally, the specific immobilization of rhodamin (TRITC)-conjugated streptavidin on the biotinylated polymeric adlayer was achieved by a simple microcontact printing technique, resulting in well-defined patterns of the protein.