A retinyl palmitate-loaded solid lipid nanoparticle system: Effect of surface modification with dicetyl phosphate on skin permeation in vitro and anti-wrinkle effect in vivo

Surface-modified solid lipid nanoparticles (SLNs) containing retinyl palmitate (Rpal) were prepared by the hot-melt method using Gelucire 50/13® and Precirol ATO5®. Dicetyl phosphate (DCP) was added to negatively charge the surfaces of the SLNs and thereby enhance the skin distribution properties of Rpal. In vitro skin permeation and in vivo anti-aging studies were performed using SLNs dispersed in a hydrogel. The SLNs were under 100 nm in size with an even polydispersity index (PDI), and the high absolute zeta-potential value was sufficient to maintain the colloidal stability of the SLNs. DCP-modified negative SLNs (DCP_mod-SLNs) enhanced the skin distribution of Rpal 4.8-fold and delivered Rpal to a greater depth than did neutral SLNs. The in vivo anti-wrinkle effect of the DCP_mod-SLN formulation was Rpal dose-dependent. However, the anti-wrinkle effects of the DCP_mod-SLN formulations were significantly different from that of the negative control and effectively prevented the reduction of elastin and superoxide dismutase by UV irradiation. In conclusion, the DCP_mod-SLN system presented is a good candidate for topical Rpal delivery.