Non-Functionalized Gold Nanoparticles Inhibit Human Papillomavirus (HPV) Infection.

The spontaneous interaction between human papillomavirus type 16 (HPV16) L1 virus-like particles (VLPs) and non-functionalized gold nanoparticles (nfGNPs) interferes with the nfGNPs' salt-induced aggregation, inhibiting the red-blue color shift in the presence of NaCl. Electron microscopy and competition studies showed that color-shift inhibition is a consequence of direct nfGNP-VLP interaction and, thus, may produce a negative impact on the virus entry cell process. Here, an in vitro infection system based on the HPV16 pseudovirus (PsV) was used to stimulate the natural infection process in vitro. PsVs carry a pseudogenome with a reporter gene, resulting in a fluorescent signal when PsVs infect a cell, allowing quantification of the viral infection process. Aggregation assays showed that nfGNP-treated PsVs also inhibit color shift in the presence of NaCl. High-resolution microscopy confirmed nfGNP-PsV complex formation. In addition, PsVs can interact with silver nanoparticles, suggesting a generalized interaction of metallic nanoparticles with HPV16 capsids. The treatment of PsVs with nfGNPs produced viral infection inhibition at a higher level than heparin, the canonical inhibitor of HPV infection. Thus, nfGNPs can efficiently interfere with the HPV16 cell entry process and may represent a potential active component in prophylactic formulations to reduce the risk of HPV infection.

Forces during cellular uptake of viruses and nanoparticles at the ventral side.

Many intracellular pathogens, such as mammalian reovirus, mimic extracellular matrix motifs to specifically interact with the host membrane. Whether and how cell-matrix interactions influence virus particle uptake is unknown, as it is usually studied from the dorsal side. Here we show that the forces exerted at the ventral side of adherent cells during reovirus uptake exceed the binding strength of biotin-neutravidin anchoring viruses to a biofunctionalized substrate. Analysis of virus dissociation kinetics using the Bell model revealed mean forces higher than 30 pN per virus, preferentially applied in the cell periphery where close matrix contacts form. Utilizing 100 nm-sized nanoparticles decorated with integrin adhesion motifs, we demonstrate that the uptake forces scale with the adhesion energy, while actin/myosin inhibitions strongly reduce the uptake frequency, but not uptake kinetics. We hypothesize that particle adhesion and the push by the substrate provide the main driving forces for uptake.

Site-selective nucleation and controlled growth of gold nanostructures in tobacco mosaic virus nanotubulars.

Site-selective biomineralization of Au nanostructures in the interior channel of Tobacco Mosaic Virus (TMV) is achieved by mutating threonine 103 in TMV to cysteine (T103C-TMV) to introduce the strong coordination interaction between the arrayed sulfhydryl ligands and gold species. By finely tuning the reaction conditions, Au nanoparticle chains and Au nanorods are successfully and exclusively synthesized inside the T103C-TMV nanotubes.

Adsorption of rotavirus and bacteriophage MS2 using glass fiber coated with hematite nanoparticles.

Batch and flow-through experiments were conducted to investigate the removal and inactivation of rotavirus (RV) and bacteriophage MS2 using glass fiber coated with hematite nanoparticles. Batch tests showed a high removal of MS2 (2.49x10(11) plaque forming unit/g) and RV (8.9x10(6) focal forming unit/g) at a low concentration of hematite nanoparticles in solution (0.043g/L and 0.26g/L, respectively). Virus adsorption was, however, decreased in the presence of bicarbonate ions and natural organic matter (NOM) in solution, suggesting a great affinity of iron oxide nanoparticles for these competitors. Adsorption on hematite nanoparticles by MS2 and RV was also tested with aquifer groundwater under saturated flow conditions to mimic environmental conditions with promising results (8x10(8) plaque forming unit/g and 3x10(4) focal forming unit/g, respectively). Desorption of up to 63% of infectious MS2 and only 2% of infectious RV from hematite nanoparticles were achieved when an eluant solution containing beef extract and glycine was used. Transmission electron microscopy (TEM) images showed evidence of electrostatic adsorption of apparently intact MS2 and structurally damaged RV particles to hematite nanoparticles. Results from this research suggest that a cartridge made of glass fiber coated with hematite nanoparticles could be used as a point-of-use device for virus removal for drinking water treatment.

Electronic properties of molecular memory circuits on a nanoscale scaffold.

Significant challenges exist in assembling and interconnecting the building blocks of a nanoscale device and being able to electronically address or measure responses at the molecular level. Here we demonstrate the usefulness of engineered proteins as scaffolds for bottom-up self-assembly for building nanoscale devices out of multiple components. Using genetically engineered cowpea mosaic virus, modified to express cysteine residues on the capsid exterior, gold nanoparticles were attached to the viral scaffold in a specific predetermined pattern to produce specific interparticle distances. The nanoparticles were then interconnected using thiol-terminated conjugated organic molecules, resulting in a three-dimensional network. Network properties were engineered by using molecular components with different I-V characteristics. Networks consisting of molecular wires alone were compared with networks containing voltage controlled molecular switches with two stable conductance states. Using such bistable molecules enabled the formation of switchable molecular networks that could be used in nanoscale memory circuits.