Fabrication, functionalization and manipulation of magnetic nanowires for biological applications

Multi-segment, high aspect-ratio nanoparticles, or nanowires, have been fabricated by templated electrodeposition and selectively functionalized for biological applications. This selectivity was accomplished by utilizing the fact that organic molecules with appropriate ligands selectively bind to discrete segments of multisegment metal and metal oxide nanowires. As a result, multi-component nanowires with different functionalities on each segment can be attained. Two-component Ni-Au nanowires were functionalized to yield both a hydrophilic segment and a hydrophobic segment. This allowed for preferential protein adsorption on the nickel or gold segment of the nanowire. The protein resistant properties of these bifunctional nanowires were studied and quantified by optical and fluorescence microscopies.; Nanowires were introduced to mammalian cells to investigate cell-nanowire interactions; specifically self-assembly and cell separations. The deposition of nickel or ferric oxide segments enables magnetic manipulation of the nanowires with an applied magnetic field. Cell separations were performed by utilizing both the inherent magnetic properties of ferromagnetic nanowires and the ability to chemically modify nanowire surfaces. Single- and multi-segment magnetic nanowires provide an excellent platform for cell manipulations because their large magnetic moments allow for the application of large forces to cells. Cell separations based on the magnetic properties of nanowires show increased effectiveness compared to magnetic beads.; Additionally, cell separations taking advantage of surface functionalization techniques enabled the binding of a cell specific antibody to nanowires. For example, nickel nanowires have been functionalized with mouse anti-human E-cadherin antibody, which shows selectivity toward epithelial cells. Magnetic separation revealed an enhancement in the population of this cell type from a heterotypic culture.; Lastly, magnetic nanowires and cells bound to nanowires will align head-to-tail in an applied magnetic field. The dynamics of nanowire "chain" formation were studied by video microscopy and quantatively modeled. This demonstrates a new approach for selfassembly and the ability to manipulate cells for biological applications.