4-Methylbenzylidene camphor microspheres: Reconstituted epidermis (Skinethic®) permeation and distribution

Synopsis Objective The UV filter 3(4-methylbenzylidene) camphor (4-MBC) is a common ingredient in sunscreen cosmetic products. However, different 'in vitro' and 'in vivo' studies suggest that 4-MBC can cause endocrine disrupting effects. Therefore, there is a need for new systems able to minimize the skin penetration of this UV filter. The aim of this study was to evaluate cutaneous permeation and distribution, through and into EPISKIN reconstituted epidermis (RE) from an O/W emulsion containing 4-MBC free or encapsulated in polymeric substantive microspheres. Methods Microspheres containing 4-MBC were prepared using the emulsification-solvent evaporation method and characterized for shape and surface morphology and encapsulation efficiency. O/A emulsions containing sunscreen free or encapsulated in microspheres were undergone to permeation tests through RE using vertical diffusion cells. At the end of the in vitro permeation experiments, the skin was subjected to tape stripping procedure to separate stratum corneum from viable epidermis. Each part was properly treated to extract the sunscreen retained and subject to quantitative analysis. Results The encapsulation of the sunscreen in the microspheres remarkably reduced the permeation of 4-MBC and increased its retention on the skin surface where its action is more desirable. Conclusions The results of this study confirm the validity of substantive microspheres as an ideal formulation candidate to use in sunscreen preparation as they appear minimizing its systemic uptake and the potential associate toxicological risks. Therefore, more of the active sunscreen remains on the surface of the skin where it is intended to act and a higher activity it will explicate.