Retinyl palmitate-loaded nanostructured lipid carriers prepared by the phase inversion temperature method: Physicochemical properties, in vitro skin permeation, and occlusion ability.

Nanostructured lipid carriers (NLCs) have emerged as a promising approach to improve the stability and dermal delivery of retinyl palmitate (RP), a widely used anti-ageing ingredient. This study developed RP-loaded NLCs using the phase inversion temperature method for topical delivery. In this study, RP was encapsulated into NLCs prepared by the phase inversion temperature method. The optimised formulation comprised 2% polysorbate 20, a 5:5 ratio of glyceryl monostearate to cetyl palmitate, and a 6:4 solid-to-liquid lipid ratio. The resulting RP-NLCs displayed favourable physicochemical properties, including a particle size of 119.0 ± 3.7 nm, polydispersity index of 0.039 ± 0.005, zeta potential of -22.6 ± 0.6 mV, and high encapsulation efficiency (94.49 ± 0.01%). The nanoparticles were spherical with a low recrystallinity index (10.98%). RP-NLCs significantly enhanced skin penetration, and the 0.1% RP-NLC gel demonstrated good occlusive ability, supporting their potential in advanced anti-ageing formulations.