Research studies done on percutaneous absorption of TiO2 and ZnO nanoparticles.
Test material
Skin model
Particle size
Results
Reference
Ti
Dermatomed skin
1–35 nm, (noncoating), 2–35 nm (alumina/silica/silicon coated), and 3–10 100 nm (mixture of alumina and silicon coated)
No penetration was observed regardless of Ti type in intact and stripped skin. SEM-EDS observation showed that Ti penetrated into vacant hair follicles (greater than 1 mm below the skin surface); however it did not penetrate into dermis and viable epidermis.
TiO2 or ZnO nanoparticles are absent or their concentration is too low to be tested under the stratum corneum in human viable epidermis. Therefore, significant penetration towards the underlying keratinocytes is unlikely.
Results showed penetration is limited to upper layers of stratum corneum. No penetration in skin furrows or follicular opening may be mistaken for penetration in the epidermal compartment.