Bacteriophages possess several characteristics that make them ideally suited for use as templates in the facile assembly of spatially-defined arrays of inorganic nanoparticles. Bacteriophage particles have highly regular, symmetrical geometries and surface properties and have dimensions from tens to hundreds of nanometers, enabling their self-assembly into ordered arrays via evaporation-driven processes. Additionally, bacteriophages possess relatively simple genomes, and their protein capsids can be easily engineered to express non-native functional groups or ligands at specific surface locations that react with various inorganic nanoparticles. Co-assembly of genetically-modified bacteriophages and nanoparticles can, therefore, be used to produce highly ordered 2D devices in which the geometry, size, and reactivity of the bacteriophage template can be controlled to create new nanoparticles architectures with unique properties. We have engineered virus-like particles (VLPs) that have identical surface characteristics to the 28-nm, icosahedral bacteriophages, MS2 and Qβ, but that express non-native peptide sequences at 180 evenly-spaced locations on their surfaces. Using an affinity process collectively called phage display, we have selected for genetically-modified VLPs that are able to nucleate the growth of various inorganic materials, and we have utilized these VLPs to nucleate and grow metal nanoparticles from their respective salts both before and after the assembly process. We have used a novel deposition technique, convective assembly, to assemble these VLPs on assorted substrates. Convective assembly enables rapid deposition of colloidal particles without employing non-biocompatible solvents by trapping microliter-sized droplets between two fixed-angle plates and dragging the ensuing meniscus with constant velocity. Deposition speed, relative humidity, and particle volume fraction can be varied to control film structure and thickness. We have assessed the influence of substrate surface chemistry and particle-particle interactions on long-range order via Grazing Incidence Small Angle X-ray Scattering (GISAXS) characterization of VLPs assembled on anionic, cationic, and non-ionic, polar surfaces and in the presence of buffers with various ionic strengths. We determined the degree to which bacteriophage particles deform or denature during the assembly process using agarose gel electrophoresis and Florescence Resonance Energy Transfer (FRET). We also used sol-gel processing techniques to create superhydrophobic surfaces that can be patterned by UV-ozone exposure to generate alternating hydrophobic and hydrophilic regions; bacteriophages have a net negative charge at biologically-relevant pH values and, therefore, selectively wet hydrophilic regions, enabling us to construct patternable nanoparticle-based devices.

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

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