Nanomaterials For Detection Research Articles

Enhanced Dark-Field Hyperspectral Imaging and Spectral Angle Mapping for Nanomaterial Detection in Consumer Care Products and in Skin Following Dermal Exposure.

Consumer personal care products, and cosmetics containing nanomaterials (NM), are increasingly available in the Canadian market. Current Canadian regulations do not require product labeling for ingredients that are present in the nanoscale. As a result, unless voluntarily disclosed, it is unclear which products contain NM. The enhanced dark-field hyperspectral imaging (EDF-HSI) coupled with spectral angle mapping (SAM) is a recent technique that has shown much promise for detection of NM in complex matrices. In the present study, EDF-HSI was used to screen cosmetic inventories for the presence of nano silver (nAg), nano gold (nAu), and nano titanium dioxide (nTiO2). In addition, we also assessed the potential of EDF-HSI as a tool to detect NM in skin layers following application of NM products in vitro on commercially available artificial skin constructs (ASCs) and in vivo on albino hairless SKH-1 mouse skin. Spectroscopic analysis positively detected nAu (4/9 products) and nTiO2 (7/13 products), but no nAg (0/6 products) in a subset of the cosmetics. The exposure of ASCs for 24 h in a Franz diffusion cell system to a diluted cosmetic containing nTiO2 revealed penetrance of nTiO2 through the epidermal layers and was detectable in the receptor fluid. Moreover, both single and multiple applications of nTiO2 containing cosmetics on the dorsal surface of SKH-1 mice resulted in detectable levels of trace nTiO2 in the layers of the skin indicating that penetrance of NM was occurring after each application of the product. The current study demonstrates the sensitivity of EDF-HSI with SAM mapping for qualitative detection of NM present in cosmetic products per se and very low levels in complex biological matrices on which these products are applied.

Multi-scale X-ray computed tomography to detect and localize metal-based nanomaterials in lung tissues of in vivo exposed mice

In this methodological study, we demonstrated the relevance of 3D imaging performed at various scales for the ex vivo detection and location of cerium oxide nanomaterials (CeO2-NMs) in mouse lung. X-ray micro-computed tomography (micro-CT) with a voxel size from 14 µm to 1 µm (micro-CT) was combined with X-ray nano-computed tomography with a voxel size of 63 nm (nano-CT). An optimized protocol was proposed to facilitate the sample preparation, to minimize the experimental artifacts and to optimize the contrast of soft tissues exposed to metal-based nanomaterials (NMs). 3D imaging of the NMs biodistribution in lung tissues was consolidated by combining a vast variety of techniques in a correlative approach: histological observations, 2D chemical mapping and speciation analysis were performed for an unambiguous detection of NMs. This original methodological approach was developed following a worst-case scenario of exposure, i.e. high dose of exposure with administration via intra-tracheal instillation. Results highlighted both (i) the non-uniform distribution of CeO2-NMs within the entire lung lobe (using large field-of-view micro-CT) and (ii) the detection of CeO2-NMs down to the individual cell scale, e.g. macrophage scale (using nano-CT with a voxel size of 63 nm).

An electron microscopy based method for the detection and quantification of nanomaterial number concentration in environmentally relevant media

Improved detection and characterization of nanomaterials (NMs) in complex environmental media requires the development of novel sampling approaches to improve the detection limit to be close to environmentally realistic concentrations. Transmission electron microscopy (TEM) is an indispensable metrological tool in nanotechnology and environmental nanoscience due to its high spatial resolution and analytical capabilities when coupled to spectroscopic techniques. However, these capabilities are hampered by the conventional sample preparation methods, which suffer from low NM recovery. The current work presents a validated, fully quantitative sampling technique for TEM that overcomes conventional sample preparation shortcomings, and thus enables the use of TEM for measurement of particle number concentration and their detection in complex media at environmentally realistic concentrations. This sampling method is based on ultracentrifugation of NMs from suspension onto a poly-l-lysine (PLL) functionalized TEM grid, using active deposition (by ultracentrifugation) and retention (by PLL interactions with NM surface) of NMs on the substrate, enabling fully quantitative analysis. Similar analysis with AFM was satisfactory in simple media but the lack of chemical-selectivity of AFM limits its applicability for the detection of NMs in complex environmental samples. The sampling approach was validated using both citrate- and PVP-coated AuNMs in pure water, which demonstrated an even distribution of NM on the TEM grid and high NM recovery (80–100%) at environmentally relevant NM concentrations (ca. 0.20–100μgL−1). The applicability of the sampling method to complex environmental samples was demonstrated by the quantification of particle number concentration of AuNMs in EPA soft water (with and without Suwannee River fulvic acid) and lake water. This sample preparation approach is also applicable to other types of NMs with some modifications (e.g. centrifugation force and time) to insure full sample recovery. This TEM sampling method is key to the accurate quantification of NM number concentration, and therefore to improving our understanding of environmental fate, behavior, effects and dose of NMs.