CuO nanoparticles penetration through intact and damaged human skin
The great antimicrobial action of copper oxide nanoparticles (CuO NP) and the consequent diffusion of many applications in the biomedical field, cause concern about potentially negative effects of human skin exposure to CuO NP. However very few studies investigated so far the toxic action of CuO NP toward humans, with a special focus to skin penetration route of entry. This study considers for the first time the absorption of topically applied CuO NP through human skin, using a Franz static diffusion cell model. We characterised colloidal behaviour and static dissolution of commercially bare CuO NP, evaluating both intact and damaged skins. We tested physiological solution as receiving phase, and as donor phase CuO NP dispersed in synthetic sweat and exposed to the outer surface of the skin (0.11 mg cm−2) for 24 hours. The Cu elemental analysis in the receptor fluid and in the exposed skin allowed to quantify copper translocation within epidermis and dermis. The experimental data showed that CuO NP absorption through intact skin was negligible, while in damaged skin we observed an increasing permeation of copper. The last would justify the capacity of CuO NP to pass the first layers and to release Cu2+ ions in the stratum corneum, reaching the receptor fluid in the in vitro diffusion cell system.