Focus on Skin as a Possible Port of Entry for Solid Nanoparticles and the Toxicological Impact

This review from 2010 examined the skin as a potential entry point for solid nanoparticles (NPs) and their toxicological impact. It highlighted that NPs are primarily found in hair follicle openings and on the stratum corneum surface, with some studies indicating deeper penetration into the viable epidermis and dermis, particularly for 4 to 5 nm quantum dots. NP interactions with skin cells could lead to cytotoxicity and immune responses, especially in damaged skin. The review noted that characteristics promoting NP skin penetration were unclear, and there were significant data gaps regarding particles smaller than 10 nm. It also pointed out the potential cytotoxicity and genotoxicity of sunscreen NPs like TiO2 and ZnO. The review called for standardization of test systems and a focus on correlating physicochemical properties of NPs with their penetration potential.