Miles F. Beaux

Principles and mechanisms of gas sensing by GaN nanowires functionalized with gold nanoparticles

Electrical properties of a chemical sensor constructed from mats of GaN nanowires decorated with gold nanoparticles as a function of exposure to Ar, N2, and methane are presented. The Au nanoparticle decorated nanowires exhibited chemically selective electrical responses. The sensor exhibits a nominal response to Ar and slightly greater response for N2. Upon exposure to methane the conductivity is suppressed by 50% relative to vacuum. The effect is fully reversible and is independent of exposure history. We offer a model by which the change in the current is caused by a change in the depletion depth of the nanowires, the change in the depletion depth being due to an adsorbate induced change in the potential on the gold nanoparticles on the surface of the nanowires.

Differential cytotoxicity exhibited by silica nanowires and nanoparticles

Silica nanowires are one-dimensional nanomaterials that are being developed for use in biological systems. Unfortunately, little is known regarding the cytotoxic potential of this type of nanomaterial. Here, using two different human epithelial cell lines we have examined the cytotoxicity of silica nanowires over a broad concentration range. The results indicate that silica nanowires are nontoxic at concentrations below 190 µg/ml but exhibit considerable cytotoxicity at higher concentrations. Examination of the mechanisms responsible for nanowire-induced cytotoxicity indicates that apoptotic pathways are not activated. Instead, cytotoxicity appears to be primarily due to increased necrosis in cells exposed to high concentrations of nanowires. In contrast to what was seen with silica nanowires, analysis of silica nanoparticles revealed very little cytotoxicity even at the highest concentrations tested. These results indicate that structural differences between silica nanomaterials can have dramatic effects on interaction of these nanomaterials with cells.

In vitro proliferating cell models to study cytotoxicity of silica nanowires

UNLABELLED Proliferating cells representing two disease models (HeLa and Panc 10.05 cells) and a more physiologically relevant cell model (3T3-L1 cells) were used to study the acute toxicologic effects of silica nanowires (NWs). Cellular responses to NW effects were determined over a 4- to 20-hour exposure time-course. Proliferation, viability, metabolic activity, and toxicologic mechanism (apoptosis vs. necrosis) data showed the following: 3 x 10(4) NWs per cell inhibited cell proliferation. The effect was rapid in HeLa cells, but 3T3-L1 and Panc 10.05 cells appeared to be more tolerant to NWs, effects being significant only after 20 or 16 hours, respectively. Cells of all three cell lines showed a significant reduction in cellular metabolic activity after 20 hours of treatment with NWs. Assay of NW-invoked mechanism of cell death (caspase 3/7 activity) indicated that apoptosis was minimally induced. Small but significant effects of NWs were detected in 3T3-L1 and HeLa cells after 20-hour treatment. No NW-induction of caspase 3/7 activity was detected for Panc 10.05 cells. Proliferating cells provide a sensitive model to study treatment with silica NWs. Silica NWs appeared to be well tolerated by these three cell lines at the doses tested. When effects were detected, cell necrosis and not apoptosis was the main mechanism of silica NW-induced cell death. FROM THE CLINICAL EDITOR In this study, three relevant cell culture models were used to study the acute toxicological effects of silica nanowires (NW). All cell lines cells showed a significant reduction in cellular metabolic activity after 20 h of treatment with NW. Overall, silica NW appeared to be well-tolerated by these cell lines at the tested doses. Cell necrosis as opposed to apoptosis was the main mechanism of silica NW-induced cell death.

Utilization of solid nanomaterials for drug delivery.

Background: Solid nanostructures are versatile platforms for constructing hybrid drug delivery systems that have tremendous potential for improving disease prevention and treatment. The rationale and application of solid nanostructures in the context of drug delivery are explored in this article. Objective: The purpose of this paper is to provide a concise review of the major attributes of solid nanostructures as they relate to drug delivery and to describe the outstanding issues that need to be addressed in order to develop these materials into clinically useful reagents. Methods: The scope of this opinion has been restricted to solid nanostructures, where solid nanostructures are defined as those that are not biodegradable. The opinion has been further limited to the three primary types of nanostructures: nanoparticles, nanowires and nanotubes. Results/conclusion: There is a need for cross-disciplinary training and standardized protocols for developing and evaluating the efficacy of solid nanomaterials.

Reynolds number manipulation of mean nanowire lengths and nanowire suspension quantification

A process has been developed for post fabrication manipulation of silica nanowire lengths with reproducible mean length target ability by manual grinding in liquid media. The process is based on the relationship between nanowire Reynolds number and the laminar or turbulent motion of nanowires in a media. Mean lengths of nanowires prepared by this process are predicted to be inversely proportional to the density over viscosity of the media used. Experimental results giving the mean length measurements are in very good agreement with the predicted dependence on medium density and viscosity.