Bicelles and bicosomes as free radical scavengers in the skin

In the present work, β-carotene antioxidant was incorporated in two different lipid nanoaggregates, bicelles and bicosomes, and its effectiveness against free radical formation in porcine skin in vitro was determined using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) spin trap and Electron Paramagnetic Resonance spectroscopy (EPR). Bicelles are discoidal nanostructures formed by self-assembly of phospholipids dispersed in aqueous solution. Bicosomes emerge as a strategy to stabilize and protect bicelles encapsulating these nanostructures in liposomes. Results from Dynamic Light Scattering (DLS) and cryo Transmission Electron Microscopy (cryo-TEM) demonstrated a slight modification in the size of both systems when β-carotene was incorporated. EPR revealed that after skin irradiation both systems presented free radical scavenging activity. This activity was statistically significant for bicosomes containing β-carotene. Differences regarding this scavenging activity between bicelles and bicosomes would probably be due to the different interaction of both systems with the skin. In this study, six different radicals were identified in skin spectra: two originated from oxygen centred radicals (primary/secondary and tertiary alkoxyl radicals) and another from carbon-centred radicals. Additionally, the presence of 5,5-dimethyl-2-oxo-pyrroline-1-hydroxyl (DMPO-OH), 5,5-dimethyl-2-oxo-pyrroline-1-hydrogen (DMPO-H) adducts and aminoxyl radicals (RR′NO&z.rad;) were detected. Considering these results, bicelles and bicosomes could be useful lipid systems for future dermopharmaceutical applications. β-carotene is incorporated in bicelle and bicosome lipid systems. Once applied on the skin, these systems show radical scavenging effect in this tissue under UV radiation. At least five different radicals are observed in the skin.