Biomineralized anisotropic gold microplate-macrophage interactions reveal frustrated phagocytosis-like phenomenon: a novel paclitaxel drug delivery vehicle.

This study reports a facile biomineralization route for gold microplates (GMPs) synthesis using bovine serum albumin (BSA) as a reductant and stabilizing agent. Adding BSA to HAuCl4 solution yields spontaneous versatile anisotropic and partially hollow GMPs upon aging. We hypothesize that the instantaneous protein denaturation at low pH enabled access to serine and threonine hydroxyl, and sulfhydryl groups of BSA, which act as a reductant and stabilizer, respectively. This reaction could be hastened by increasing the temperature well beyond 65 °C. Transmission electron microscopy/X-ray diffraction studies revealed highly crystalline and anisotropic structures (triangle, pentagon, and rectangle). Atomic force microscopy/scanning electron microscopy analyses demonstrated unique morphology of microplates with a partially void core and BSA mineralized edge structure. RAW 264.7 mice peritoneal macrophage-microplate interaction studies using live cell confocal imaging reveal that cells are capable of selectively internalizing smaller GMPs. Large GMPs are preferentially picked with sharp vertices but cannot be internalized and exhibit frustrated phagocytosis-like phenomenon. We explored particle phagocytosis as an actin mediated process that recruits phagosome-like acidic organelles, shown by a lysosensor probe technique. The biocompatible GMPs exhibited ∼70% paclitaxel (PCL) loading and sustained release of PCL, showing antitumor activity with the MCF-7 cell line, and could be a novel drug carrier for breast cancer therapy.

Antimicrobial activity of silica coated silicon nano-tubes (SCSNT) and silica coated silicon nano-particles (SCSNP) synthesized by gas phase condensation.

Silica-coated, silicon nanotubes (SCSNTs) and silica-coated, silicon nanoparticles (SCSNPs) have been synthesized by catalyst-free single-step gas phase condensation using the arc plasma process. Transmission electron microscopy and scanning tunneling microscopy showed that SCSNTs exhibited a wall thickness of less than 1 nm, with an average diameter of 14 nm and a length of several 100 nm. Both nano-structures had a high specific surface area. The present study has demonstrated cheaper, resistance-free and effective antibacterial activity in silica-coated silicon nano-structures, each for two Gram-positive and Gram-negative bacteria. The minimum inhibitory concentration (MIC) was estimated, using the optical densitometric technique, and by determining colony-forming units. The MIC was found to range in the order of micrograms, which is comparable to the reported MIC of metal oxides for these bacteria. SCSNTs were found to be more effective in limiting the growth of multidrug-resistant Staphylococcus aureus over SCSNPs at 10 µg/ml (IC 50 = 100 µg/ml).

Proteome analysis of mouse macrophages treated with anthrax lethal toxin.

Anthrax toxin produced by Bacillus anthracis is a tripartite toxin comprising of protective antigen (PA), lethal factor (LF) and edema factor (EF). PA is the receptor-binding component, which facilitates the entry of LF or EF into the cytosol. EF is a calmodulin-dependent adenylate cyclase that causes edema whereas LF is a zinc metalloprotease and leads to necrosis of macrophages. It is also important to note that the exact mechanism of LF action is still unclear. With this view in mind, in the present study, we investigated a proteome wide effect of anthrax lethal toxin (LT) on mouse macrophage cells (J774A.1). Proteome analysis of LT-treated and control macrophages revealed 41 differentially expressed protein spots, among which phosphoglycerate kinase I, enolase I, ATP synthase (beta subunit), tubulin beta2, gamma-actin, Hsp70, 14-3-3 zeta protein and tyrosine/tryptophan-3-monooxygenase were found to be down-regulated, while T-complex protein-1, vimentin, ERp29 and GRP78 were found to be up-regulated in the LT-treated macrophages. Analysis of up- and down-regulated proteins revealed that primarily the stress response and energy generation proteins play an important role in the LT-mediated macrophage cell death.