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.