In addition these particles, because of their crystallinity, can scatter/refl ect incoming UV radiation, increasing the sun protection factor. A be nefi cial characteristic of NPSUNs is their high skin substantivity which could min- imize the need for repetitive applications. Such a characteristic, along with the factor of non-penetrability, makes NPSUNs highly applicable. More over, incorporation in LMs of combination of sunscreen substances is signifi cantly effective in enhancing the UVA fi lter photostability. SBA- 15, an innovative mesoporous material, increased photoprotection by UV fi lters while reducing their cutaneous penetration and transdermal permeation. Mesoporous silica materials of type SBA-15 are nontoxic and biocompatible, and the presence of an ordered pore network with homogeneous pore size enables a good and reproducible con- trol of drug loading and a benefi cial release profi le. Furthermore, the high pore volume and large surface area facilitate drug loading and drug adsorption. Cons equently, a development of formulas based on non-penetrating photo protectors is considered to be more than relevant. This explains why the biggest challenge cosmetolo- gists face is the development of appropriate products that could hinder skin penetration. ACKN OWLEDGMENTS This article is a literature review completed in the frame of research undertaken in Labo- ratory of Chemistry-Biochemistry-Cosmetic Science, Division of Aesthetics and Cosmetic Science, Department of Biomedical Sciences, the University of West Attica (Egaleo, Greece), supported by an Academic Scholarship. Assistance with useful data and con- structive recommendations was provided by colleagues of the Section of Pharmaceutical Technology, Department of Pharmacy, School of Health Sciences, National and Kapodis- trian University of Athens. DECL A RATION OF INTEREST The authors have no declaration of interest. The authors alone are responsible for the content and writing of the manuscript. REFE RENCES (1) P . Pavlou, M. Rallis, G. Deliconstantinos, G. Papaioannou, and S. Grando, In-vivo data on the infl u- ence of tobacco smoke and UV light on murine skin, Toxicol. Ind. Health, 25(5), 231–239 (2009). (2) M . Schlumpf, P. Schmid, S. Durrer, M. Conscience, K. Maerkel, M. Henseler, M. Gruetter, I. Herzog, S. Reolon, R. Ceccatelli, O. Faass, E. Stutz, H. Jarry, W. Wuttke, and W. Lichtensteiger, Endocrine activity and developmental toxicity of cosmetic UV fi lters - an update, Toxicology, 205(1-2), 113–122 (2004). (3) S . T. Butt and T. Christensen, Toxicity and phototoxicity of chemical sun fi lters. Radiat. Prot. Dosimet., 91(1-3), 283–286 (2009). (4) K . M. Hanson, E. Gratton, and C. J. Bardeen, Sunscreen enhancement of UV-induced reactive oxygen species in the skin. Free Radic. Biol. Med., 41(8), 1205–1212 (2006). (5) J . F. Nash and P. R. Tanner, Relevance of UV fi lter/sunscreen product photostability to human safety. Photodermatol. Photoimmunol. Photomed., 30, 88–95 (2014). (6) J . V. Freitas, N. P. Lopes, and L. R. Gaspar, Photostability evaluation of fi ve UV-fi lters, trans-resveratrol and beta-carotene in sunscreens, Eur. J. Pharm. Sci., 78, 79–89 (2015). JOURNAL OF COSMETIC SCIENCE 320

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