Visualization of in vitro uptake of nail lacquer ingredients into nail plate by high‐resolution SIMS imaging [* Cross-Reference *]

Introduction: Bovine hoof sheets (BHS) as a model for the human nail plate have been widely used to analyze drug uptake and partition coefficients of topically applied products on nails [1].In the present proof of concept (PoC) study, the in vitro distribution of selected cosmetic lacquer ingredients into the BHS was investigated by high-resolution Secondary Ion Mass Spectrometry (nano-SIMS, [2]) imaging.In toxicology and epidemiology, human nails are known biomarkers of metal and nonmetal exposure in domestic or environmental conditions [3][4].Their sulfur content and mineral composition are also useful indicators for nutritional deficiencies and nail disease [5].Topical aluminium [6-7] and titanium dioxide [8] in cosmetics and personal care products are of concern about their safety.Methods: commercial cosmetic CATRICE ICONAILS Gel Lacquer 105 was selected due to soluble components, microparticles and metal oxides not of natural origin in the nail.Ingredients investigated were titanium dioxide, iron oxide, aluminium powder, micrometer-scaled mica particle fluorphlogopite and soluble pigments containing sulfur.After 24 h contact of lacquer film topically exposed to BHS surface, BHS were embedded in resin and adjusted crosswise by ultramicrotomy.A NanoSIMS 50 (CAMECA, France) instrument was used to map the distribution of 23 Na + , 27 Al + , 28 Si + , 40 Ca + , 50 Ti + , 56 Fe + , 12 C 14 N -, 32 S -, 27 Al 16 O - and 56 Fe 16 O -on BHS cross-section.Results: in the control sample, Na and Ca were evenly distributed in punctual structures.In particular for Na, connecting channels between cavities were found, which are in line with earlier scanning electron microscopy and X-ray microtomography investigations [9].The non naturally occurring elements in nails Al, Ti and Fe could be excluded.Si a naturally occurring element could be detected.Lacquer exposure led to an uptake of organic material ( 12 C 14 N - detection) in the cavities and an accumulation on the BHS surface.S originating from sulfonic acids in soluble pigments penetrated along the connecting channels into the plate.Fluorphlogopite particles (10-150 m) [10] could only be resolved on the BHS surface via superposition of Al and Si signal.AlO and Si distributions indicate a penetration from solubilized or small-scaled particles of fluorphlogopite, whereas an uptake of FeO could be excluded.Conclusion: our PoC study demonstrated the valuable contribution of nano-SIMS technology to characterize the uptake and visualize the distribution of soluble and particular components in the nail plate for safety, efficiency and pathways investigations (environment, cosmetics and pharmaceutics). (2023-08-01)

***This entry has been automatically imported via OpenAlex by LIST harvest scripts. Please refer to https://doi.org/10.1002/lemi.202359042 for the original and latest version of the publication*** (2026-07-01)