Generic surface modification strategy for sensing applications based on Au/SiO2 nanostructures

A generic protocol for the creation of material-mediated self-assembled patterns of streptavidin, defined solely by patterns of gold and SiO2, is presented. Protein-adsorption resistance of selected regions was obtained by material-specific adsorption of thiol-modified poly(ethylene)glycol (thiol-PEG) on gold followed by adsorption of poly-L-lysine (PLL) modified PEG (PLL-g-PEG) on SiO2. Selective streptavidin binding to either gold or SiO2 (or both) was ensured by introducing biotin-modified thiolated (thiol-biotin) and/or biotin-modified PLL-g-PEG (PLL-g-PEGbiotin) compounds. The introduction of biotin did not influence the protein-adsorption resistance. On the macroscopic scale, the protein-adsorption-resistant properties and the streptavidin-binding capacity were optimized using quartz crystal microbalance with dissipation monitoring. The reproduction of micrometer-scale gold patterns on SiO2 into patterns of streptavidin was verified using fluorescence microscopy, while the compatibility of the material-specific surface-modification strategy with nanoscale features was accomplished by modifying a localized surface plasmon resonance (LSPR) active template, defined by randomly distributed nanoapertures in a thin gold film on SiO2. The demonstrated compatibility of the latter substrate with LSPR-based label-free sensing of biorecognition reactions, combined with the fact that all compounds utilized are commercially available, makes the surface-modification protocol attractive as a generic surface modification solution for a broad range of biorecognition-based assays. (C) 2007 American Vacuum Society.