On the follicular pathway of percutaneous uptake of nanoparticles: Ion microscopy and autoradiography studies

We report on the visualization of the penetration of sunscreen formulations containing TiO2 nanoparticles (about 20 nm primary particle size) into hair follicles of both human and porcine skin using the complementary methods of ion microscopy (PIXE, RBS, STIM) and autoradiography. Particles were found as deep as approx. 400 μm in the follicle, obviously introduced mechanically rather than by a diffusive process. No particles were observed in vital tissue nor in sebaceous glands.