Human skin penetration of cobalt nanoparticles through intact and damaged skin

Cobalt nanoparticles (CoNPs) are produced for several industrial and biomedical applications but there is a lack of data on human cutaneous absorption. Cobalt is also a skin sensitizer that can cause allergic contact dermatitis. Co applied as NPs, due to their small size and high surface, can penetrate into the skin in higher amount that bulk material. The aim of this study was to evaluate the absorption of Co applied as NPs in both intact and damaged skin. Experiments were performed using Franz cells and 1.0 mg cm(-2) of CoNPs was applied as donor phase for 24 h. Mean Co content of 8.5 +/- 1.2 ng cm(-2) and 1.87 +/- 0.86 mu g cm(-2) were found in the receiving solutions of Franz cells when the CoNPs suspension was applied on intact skin and on damaged skin, respectively. Twenty-four hours Co flux permeation was 76 +/- 49 ng cm(-2) h(-1) in damaged skin with a lag time of 2.8 +/- 2.1 h. This study suggests that Co applied as NPs is able to penetrate the human skin in an in vitro diffusion cell system. (C) 2012 Elsevier Ltd. All rights reserved.