Selective assembly of multi-component nanosprings and nanorods.

This communication proposes a new approach to create complex hierarchical nano-to-meso-scale architectures based on the use of biological connector molecules to direct the assembly of uniquely shaped multi-component nanostructures fabricated using glancing angle deposition (GLAD). Multiple sets of 50-nm-wide and 150 to 650-nm-tall Si-Cr/Au multi-stack zigzag nanosprings and nanorods are grown by GLAD on Si substrates. Nanorods, chosen for selective assembly, are detached from the substrate, suspended in an aqueous solution, and their surfaces are selectively functionalized by attaching biotin and streptavidin connector-molecules to the Au-regions. Successive mixing of different suspensions leads to the end-to-end assembly of long and short nanorods. This technique provides the path to build hybrid nano-architectures including nano-honeycombs, nanoladders, and 3D nanorod networks, comprised of controlled material combinations.

Positioning of quantum dots on metallic nanostructures.

The capability to position individual emitters, such as quantum dots, near metallic nanostructures is highly desirable for constructing active optical devices that can manipulate light at the single photon level. The emergence of the field of plasmonics as a means to confine light now introduces a need for high precision and reliability in positioning any source of emission, which has thus far been elusive. Placing an emission source within the influence of plasmonic structures now requires accuracy approaching molecular length scales. In this paper we report the ability to reliably position nanoscale functional objects, specifically quantum dots, with sub-100-nm accuracy, which is several times smaller than the diffraction limit of a quantum dot's emission light. Electron beam lithography-defined masks on metallic surfaces and a series of surface chemical functionalization processes allow the programmed assembly of DNA-linked colloidal quantum dots. The quantum dots are successfully functionalized to areas as small as (100 nm)(2) using the specific binding of thiolated DNA to Au/Ag, and exploiting the streptavidin-biotin interaction. An analysis of the reproducibility of the process for various pattern sizes shows that this technique is potentially scalable to the single quantum dot level with 50 nm accuracy accompanied by a moderate reduction in yield.

Poliovirus recombinants expressing hepatitis B virus antigens elicited a humoral immune response in susceptible mice.

Expression of foreign antigens in the context of poliovirus vectors may provide a plausible approach to vaccine development. Poliovirus recombinants were constructed by fusing preS surface or core HBV proteins to the poliovirus polyprotein as previously described (Andino et al., Science, 265, 1448-1451, 1994). All recombinant viruses replicated with near wild-type efficiency in tissue culture cells and stably expressed high levels of the HBV antigens. The kinetics of recombinant RNA synthesis were indistinguishable from that of wild-type poliovirus. Exogenous proteins were not incorporated into the poliovirus particles, but HBV core proteins self-assembled into 100S particles composed of free HBV core proteins and fusions with poliovirus capsid proteins. Mice susceptible to poliovirus infection were inoculated with recombinant virus and elicited humoral immune responses against the HBV antigens.