Novel nanocapsule of α‐lipoic acid reveals pigmentation improvement: α‐Lipoic acid stimulates the proliferation and differentiation of keratinocyte in murine skin by topical application

α-Lipoic acid is amphipathic with low molecular sulphur-containing fatty acid and has strong antioxidant effects. It has been used at the purposes of anti-ageing, treatment of diabetic neuropathy, and supplement as antioxidant. Though α-lipoic acid is normally administered in oral or injection, it has not been used in a topical use via skin because of its bad penetration. We developed the novel nanocapsule of α-lipoic acid, named α-lipoactive (nLA), to improve skin permeability. The nLA is constructed as micelles of α-lipoic acid mixed with the non-ionic surfactant, and its surface of the micelles was coated with inorganic metal salts. It is water soluble and has a diameter of approximately 8-15 nm. After nLA was applied to the murine skin, epidermal thickening was observed. It was confirmed that this effect is caused by α-lipoic acid molecule, but not by the raw material used for encapsulation. In in vivo experiments, it was found that nLA is very effective for improving UV-induced pigmentation and epidermal thickening. Our findings suggest that nanoencapsulation of α-lipoic acid is considerably effective for topical application.