Advanced lipid systems containing β-carotene: stability under UV-vis radiation and application on porcine skin in vitro

Phospholipid-based nanostructures, bicelles and bicosomes, are proposed as carriers of the antioxidant β-carotene. The stability of these nanostructures and their carotenoid cargo was evaluated in an oxidation environment induced by ultraviolet A, visible and infrared A radiation (UVA-VIS-IRA). Additionally, the effect of these nanoaggregates on non-irradiated and irradiated skin microstructure was studied. The characterization of the lipid systems was performed using dynamic light scattering (DLS) and cryo-transmission electron microscopy (Cryo-TEM) and lipid peroxidation of the systems was determined by thiobarbituric acid (TBARS) assay. Moreover, the stability of β-carotene in these lipid systems under this radiation was investigated using Raman spectroscopy. The results showed that the particle size of the bicelles did not change due to radiation. However, the size of the bicosomes increased slightly after irradiation. The TBARS assay showed the absence of peroxides in the bicelles and bicosomes, indicating the preservation of the lipid molecules under the radiation used. Raman experiments showed that bicosomes protected β-carotene from degradation induced by radiation better than liposomes or dissolution in chloroform. With respect to the skin microstructure, no changes after irradiation were observed via freeze substitution transmission electron microscopy (FSTEM). This technique also showed the presence of vesicular structures in the stratum corneum (SC) after treatment with bicosomes.