Skin absorption of metal nanoparticles: a new possible risk in the nanotechnology industry

Currently there is a lack of data demonstrating whether manufactured nanoparticles can gain access to the epidermis and derma after the skin contact The aim of this experimental study was to evaluate metal NP (Co, Ni) skin penetration using the Franz-cell method1.   Methods Skin absorption was evaluated by means of the Franz diffusion cell method with human skin, intact (n=7) and damaged with needle (n=7) in duplicate. We used Co and Ni  nanoparticles with an average particle  size of 80 and 25 nm respectively. They were disperse in ethanol 0.14 wt%. The nanoparticle solution was diluited 1:2 with synthetic sweat to reproduce human skin condition and 1200 and 1000 microg/cm2 of nanoparticles was applied to the skin.  A physiological solution was used as receiving phase. The receptor fluid measurements were performed by electro-thermal atomic absorption spectrometry. The presence of NP into the skin was studied by TEM and chemical analysis after digestion of the skin.  Results Metal NPs can permeate the skin in different amount: The concentration of nickel in the receiving phase after 24 hours was 0.0241 microg/cm2in intact skin and 5.429 in damaged skin. The concentration of Co in the receiving phase after 24 hours was 0.0043 microg/cm2 in intact skin and 1.870 microg/cm2 in damaged skin.  In damaged skin metal NP presented and higher permeation and metal are detectable into different skin layers.  Discussion Our data demonstrated that Ni and Co NP can permeate the skin in variable amount in relation to the characteristic of NP, size, coating and skin condition. The damaging of the skin increased significantly metal penetration and that suggests the need for a better protection in people and workers with skin diseases that can present an increased risk of skin penetration of metal NP with potential local or systemic effects.