Template fabrication of protein-functionalized gold-polypyrrole-gold segmented nanowires

Gold-capped, protein-modified polypyrrole (Ppy) nanowires were grown electrochemically using porous aluminum oxide as a template. The effects of the conditions of electrochemical synthesis on Ppy growth and protein (avidin or streptavidin) incorporation were studied. Streptavidin-modified nanowires grown at constant potential had better electrochemical properties and equilibrated faster when exposed to fluorescently labeled biotin than did nanowires grown by potential cycling. Solution pH had little effect on protein incorporation; however, higher pH provided slower but more reproducible growth rate of the Ppy segments. The best conditions for synthesis of streptavidin-modified Ppy nanowires were constant potential deposition at 0.75 V vs SCE in a phosphate buffer saline solution at pH 9. This method provides a straightforward route to nanowires of controlled length that can incorporate proteins for use in nanowire-based biosensors or in nanoparticle assembly through biomolecular interactions.