In vitro transdermal absorption of Al2O3 nanoparticles.

Dermal exposure to Aluminium nanoparticles (AlNPs) can occur in occupationally- and non occupationally exposed- population, due to the use of Al salts-based antiperspirants. No AlNPs transdermal permeation data exists. Our study investigated in vitro the permeation of 30-60 nm Al2O3NPs dispersed in synthetic sweat (20 g/L) using excised human skin on Franz cells. Experiments were performed using intact (experiment 1) and needle-abraded skin (experiment 2). After 24 h traces of Al were detectable in receiving solution of exposed cells (35.0 ± 6.0 ng/cm2 for intact and 88.5 ± 34.2 ng/cm2 for damaged skin, mean and SD) and in blank cells (36.3 ± 7.0 ng/cm2), without statistical significance (p = 0.08, Mann-Whitney test). The average amount of Al into intact and damaged skin samples was 3.96 ± 0.20 μg/cm2 for intact and 4.36 ± 0.47 μg/cm2 for damaged skin (p = 0.08). Al content was similar in epidermal and dermal layers of intact and damaged skin (1.95 ± 0.13 μg/cm2 and 2.31 ± 0.12 μg/cm2 epidermal, 2.01 ± 0.25 μg/cm2 and 2.05 ± 0.35 μg/cm2 dermal). Al is a trace element in human body and the amount found in receiving solutions could be due as background impurity. This data suggest a reassuring transdermal permeation profile for Al2O3NPs.