Analysis of Skin Permeability and Toxicological Properties of Amorphous Silica Particles

Nanomaterials (NMs) are defined as those which have nanostructured components less than 100 nm in diameter. They are widely used in various fields such as medicine, cosmetics, and the food industry. However, the toxicological effects of NMs are less well understood than their applications. In particular, the skin is exposed to the environment at all times, so is easily influenced by NMs. In this study, we investigated the skin permeability and toxicological properties of well-dispersed amorphous silica particles with diameters ranging from 70 to 1000 nm, to aid in the safe application of NMs. Amorphous silica particles of 70 nm in size (nSP70) penetrated the living epidermis, following pretreatment with acetone/diethyl ether to improve skin permeation. The application of unmodified nSP70, carboxyl group-modified nSP70, or amino group-modified nSP70 for long durations caused little skin irritation at the application site. Under the present experimental conditions, few adverse systemic effects were evident from blood tests and histopathologic examination. These results suggest that decreasing particle size increases the NMs skin permeability, but remarkably little corresponding skin irritation is observed.