MicroRNA conjugated gold nanoparticles and cell transfection.

While the importance of microRNAs (miRNAs) in cancer treatment or manipulation of genetic expression has been increasingly recognized for developing miRNA-based therapies, the controlled delivery of miRNAs into specific cells constitutes a challenging task. This report describes preliminary findings from an investigation of the conjugation of gold nanoparticles with miRNAs (miRNA-AuNPs) and their cell transfection. The immobilization of miRNAs on the AuNPs was detected, and the surface stability was substantiated by gel electrophoresis assessment of the highly charged characteristics of miRNA-AuNPs and their surface-exchange inactivity with a highly charged surfactant. The miRNA-AuNPs were tested in cell transfection using multiple myeloma cells, demonstrating efficient knockdown in the functional luciferase assay. The findings have important implications for understanding the mechanistic details of cell transfection involving miRNA-conjugated nanoparticles as biosensing or targeting probes.

All electrochemical fabrication of a platinized nanoporous Au thin-film catalyst.

In an effort to decrease the high cost associated with the design, testing, and production of electrocatalysts, a completely electrochemical scheme has been developed to deposit and platinize a nanoporous Au (NPG) based catalyst for formic acid oxidation. The proposed route enables synthesis of an alternative to the most established, nanoparticles based catalysts and addresses issues of the latter associated with either contamination inherent from the synthetic route or poor adhesion to the supporting electrode. The synthetic protocol includes as a first step, electrochemical codeposition of a Au((1-x))Ag(x) alloy in a thiosulfate based electrolyte followed by selective electrochemical dissolution (dealloying) of Ag as the less noble metal, that generates an ultrathin and preferably continuous porous structure featuring thickness of less than 20 nm. NPG is then functionalized with Pt (no thicker than 1 nm) by surface limited redox replacement (SLRR) of underpotentially deposited Pb layer to form Pt-NPG. SLRR ensures complete coverage of the surface with Pt, believed to spread evenly over the NPG matrix. Testing of the catalyst at a proof-of-concept level demonstrates its high catalytic activity toward formic acid oxidation. Current densities of 40-50 mA cm(-2) and mass activities of 1-3 A.mg(-1) (of combined Pt-Au catalyst) have been observed and the Pt-NPG thin films have lasted over 2600 cycles in standard formic acid oxidation testing.

Aggregative growth in the size-controlled growth of monodispersed gold nanoparticles.

This article describes the findings of an investigation of the aggregative growth mechanism for the formation of gold nanoparticles in aqueous solutions under ambient conditions with high monodispersity (2% RSD) over a wide range of particle sizes (10-100 nm). The utilization of the gold nanoparticles synthesized by this simple, reproducible growth mechanism has recently been demonstrated for establishing the size correlation for the surface plasmon resonance optical and surface-enhanced Raman scattering spectroscopic properties. The particle size, morphology, and optical properties of the nanoparticles produced at different stages of the growth processes were determined as a function of control parameters such as the reaction time and seed/precursor concentrations. The results have allowed us to establish a quantitative correlation between the growth size and the seed/precursor concentrations for the precise control of nanoparticle sizes. The kinetic measurements have demonstrated a polycrystalline character for the grown particles, a bimodal size distribution in the early stage of growth, sigmoidal kinetic behavior for the growth, and a correlation of the nucleation parameters with the particle size and distribution. These findings provided important indicators for the operation of an aggregative growth mechanism in the particle size growth and have important implications in understanding interparticle aggregation and coalescence in nanoparticle formation and growth under similar conditions.