(606i) Grazing Incidence Small Angle X-Ray Scattering Characterization Of 2D Self-Assembled Bacteriophage Arrays Deposited Via A Convective Transport Process

Bacteriophages are viruses that infect and replicate in bacteria and possess several characteristics that make them ideally suited for use in studying nanoparticle self-assembly into hierarchical structures. Phage populations naturally possess a high degree of monodispersity and occur in a variety of geometries similar to inorganic nanoparticles (e.g. spheres, anisotropic rods, etc.). Additionally, bacteriophages have highly regular, symmetrical geometries and dimensions from tens to hundreds of nanometers, enabling their self-assembly into ordered arrays via evaporation-driven convective transport. The self-assembly of bacteriophages with tailorable geometry, size, and surface properties into highly-ordered 2D and 3D arrays can be used to create new nanoparticle architectures with unique properties. We have used two 28-nm icosahedral coliphages, MS2 and Qβ, in conjunction with a novel deposition technique, convective assembly, to study bacteriophage self-assembly into mono- and multilayers. Convective assembly enables rapid deposition of colloidal particles onto a hydrophilic surface by trapping microliter-sized droplets between two fixed-angle plates and dragging the ensuing meniscus across a substrate with constant velocity. Deposition speed, relative humidity, and particle volume fraction can be varied to control film structure and thickness. Convective assembly is well-suited for the deposition of biological species, as it does not require the use of volatile co-solvents and minimizes material consumption. We have employed Grazing Incidence Small Angle X-ray Scattering (GISAXS) at a synchrotron source to study the time-resolved self-assembly of MS2 and Qβ at various deposition velocities, in solvents with different ionic strengths, and onto a variety of substrates. GISAXS is a preferable method to assess the structure of bacteriophage and nanoparticle arrays as it provides detailed information about the long-range order of the bulk film, whereas electron microscopy techniques only provide structural information about isolated, submicrometer-sized areas. We have found that particle-particle and particle-substrate interactions greatly influence the structure, thickness, and long-range order of bacteriophage arrays, as well as the dynamics of film formation. MS2, which has localized regions of positive and negative charges on the surface of its capsid, forms randomly-oriented mono/multilayers, while Qβ, which possesses a more disperse surface charge density, forms highly-ordered hexagonal-close packed (HCP) monolayers. The ultimate structure and long-rage order of bacteriophage arrays are highly influenced by the charge density of the hydrodynamic particle, which can be varied by changing the solvent ionic strength or by substitution of surface amino acids in the phage capsid. We have assessed the affect of charge density on MS2 and Qβ arrays by varying the ionic strength of the buffer; zeta potential and atomic force microscopy measurements have been used to supplement GISAXS data. We have, furthermore, characterized the influence of particle-substrate interactions on long-range order using hydrophobic, anionic, cationic, and non-ionic, polar surfaces and by employing 10% (v/v) glycerol as the solvent, which allows the particles to freely diffuse on the substrate. To assess the role of particle size on the convective assembly of colloids, we have used the globular protein ferritin, which is half the size of MS2 and Qβ, and have found that it assembles into disordered mono/multilayered structures. Furthermore, we have assembled phages with different geometries, such as tobacco mosaic virus, which is anisotropic, and T4 bacteriophage, which has an icosahedral head and an anisotropic tail, onto lithographically-patterned substrates with submicrometer-sized features to test whether phages with anisotropic geometries preferentially organize perpendicular to or parallel to the patterned nanochannels.