Virus-like particles: Next-generation nanoparticles for targeted therapeutic delivery.

Most drug therapies distribute the agents throughout the entire body, even though the drugs are typically only needed at specific tissues. This often limits dosage and causes discomfort and harmful side-effects. Significant research has examined nanoparticles (NPs) for use as targeted delivery vehicles for therapeutic cargo, however, major clinical success has been limited. Current work focuses mainly on liposomal and polymer-based NPs, but emerging research is exploring the engineering of viral capsids as noninfectious protein-based NPs-termed virus-like particles (VLPs). This review covers the research that has been performed thus far and outlines the potential for these VLPs to become highly effective delivery vehicles that overcome the many challenges encountered for targeted delivery of therapeutic cargo.

Characterization of [FeFe] Hydrogenase O2 Sensitivity Using a New, Physiological Approach.

[FeFe] hydrogenases catalyze rapid H2 production but are highly O2-sensitive. Developing O2-tolerant enzymes is needed for sustainable H2 production technologies, but the lack of a quantitative and predictive assay for O2 tolerance has impeded progress. We describe a new approach to provide quantitative assessment of O2 sensitivity by using an assay employing ferredoxin NADP+ reductase (FNR) to transfer electrons from NADPH to hydrogenase via ferredoxins (Fd). Hydrogenase inactivation is measured during H2 production in an O2-containing environment. An alternative assay uses dithionite (DTH) to provide reduced Fd. This second assay measures the remaining hydrogenase activity in periodic samples taken from the NADPH-driven reaction solutions. The second assay validates the more convenient NADPH-driven assay, which better mimics physiological conditions. During development of the NADPH-driven assay and while characterizing the Clostridium pasteurianum (Cp) [FeFe] hydrogenase, CpI, we detected significant rates of direct electron loss from reduced Fd to O2 However, this loss does not interfere with measurement of first order hydrogenase inactivation, providing rate constants insensitive to initial hydrogenase concentration. We show increased activity and O2 tolerance for a protein fusion between Cp ferredoxin (CpFd) and CpI mediated by a 15-amino acid linker but not for a longer linker. We suggest that this precise, solution phase assay for [FeFe] hydrogenase O2 sensitivity and the insights we provide constitute an important advance toward the discovery of the O2-tolerant [FeFe] hydrogenases required for photosynthetic, biological H2 production.

Influence of chain length on the diffusion and electrophoresis of DNA adsorbed on heterogeneous supported lipid bilayers.

This manuscript describes the influence of chain length on the diffusion and electrophoresis of single stranded DNA (ssDNA) adsorbed on heterogeneous cationic supported lipid bilayers. These studies are motivated by the increasing interest in developing novel strategies for the separation of DNA. We studied ssDNA molecules with the number of bases (N) varying from 21 to 84. Fluorescence recovery after photobleaching (FRAP) studies revealed that the diffusivity (D) of adsorbed ssDNA varied with N as D approximately N(-1), similar to a trend previously observed for the diffusion of double stranded DNA on homogeneous supported lipid bilayers. In contrast, the electrophoretic mobility of the adsorbed ssDNA in the presence of an applied tangential electric field was independent of N. Our studies indicated that the motion of ssDNA in the presence of an applied electric field was primarily due to electrophoresis and was not influenced significantly by electro-osmotic flow. Our results also suggest that the use of asymmetric diffusion barriers or other tunable obstacles may assist DNA separation on supported lipid bilayers.