Gontier, E; Habchi, C; Pouthier, T; Aguer, P; Barberet, P; Barbotteau, Y; Incerti, S; Ynsa, MD; Surleve-Bazeille, JE; Moretto, P
The ion microbeam techniques, Scanning Ion Transmission Microscopy (STIM), developed in our laboratory were associated with Particle Induced X-ray Emission (PIXE) in order to determined the presence and content of mineral ions and exogenous elements in the different strata of the skin of several mammals: mice, pig and human. PIXE and STIM were associated with Transmission Electron Microscopy to implement this analysis. PIXE and STIM allow respectively to map most elements present in epidermal sections, which appeared highly compartmentalized in the different skin strata, and to image the skin structure on the basis of its density contrast. Micro-PIXE analysis allows the simultaneous mapping of a dozen of elements (Na, Mg, S, Cl, K, Ca, Ti, Zn...) in tissues sections. STIM delivers images of tissues with sub-micrometer resolution, both rapidly and non destructively, authorizing localization of cellular structure. In addition, it allows the measurement of the sample mass to normalize X-ray data in terms of concentration. STIM method may be applied on un-embedded sections, cryofixed and freeze-dried. This sample preparation is undoubtedly an advantage when addressing percutaneous penetration studies. In new solar cream, nanoparticles of TiO2, ZnO, Al2O3, are included to provide protection againts UV. The aim of this work is to determine the potentiality of percutaneous penetration of such particles. We focused our study on formulations containing solely TiO2 nanoparticles. When such formulations were applied on skin, TiO2 particles were solely detected in the intercellular spaces between the corneocytes of the outermost layers of the stratum corneum. The TEM and PIXE studies never revealed the presence of particles within the cells of the living layers. These complementary techniques appear to be useful in providing clues to the percutaneous penetration.
