Biotemplating of metallic nanoparticle arrays through site-specific electrostatic adsorption on streptavidin crystals

The protein streptavidin exhibits unique properties advantageous for "bottom-up" nanofabrication applications. It self-assembles into various 2-D crystalline lattices onto which nanoparticles can be attached through both electrostatic and ligand-receptor mechanisms. We examine the electrostatic adsorption of gold nanoparticles onto non-close-packed streptavidin crystals and show that site-specific attachment preferentially occurs in between protein molecules. The resulting nanoparticle arrangement consequently displays a long-range structural coherence with the underlying protein lattice, although with a reduced degree of order relative to that of the biological template. Monte Carlo simulations reveal that this remittent ordering is due to (1) the random offset between the nanoparticles and their respective adsorption sites and (2) nonspecific binding to the surface of the protein molecules. Overall, our results indicate that streptavidin crystals are capable of templating ordered nanoparticle arrays.