Mesoporous Silicate MCM-41 as a Particulate Carrier for Octyl Methoxycinnamate: Sunscreen Release and Photostability

Octyl methoxycinnamate (OMC) is a widely used UV filter characterized by good absorbing properties; however, it shows light susceptibility (photoinstability) and potential skin permeation. This paper describes the application of a new particulate carrier to improve OMC safety and photostability. The UV filter was included into the pores of the mesoporous silicate MCM-41 and then entrapped there by plugging the pore openings. The last step was performed treating the MCM-41 inclusion product with a lipid cosmetic ingredient by the hot-melt method. The loaded samples were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, and N2 adsorption isotherms. Photochemical studies demonstrated that the coated samples allow a broader photoprotection range and remarkable improvement of sunscreen photostability. Finally, they were properly formulated in an emulgel, and the sunscreen release was studied in vitro by Franz diffusion cell and compared with those obtained from the same formulation containing the free filter. Sunscreen release from the studied formulations resulted negligible, meaning that the proposed approach represents a valuable strategy for UV filters stabilization toward light and safety improvement.