A novel nano-capsule of α-lipoic acid as a template of core-shell structure constructed by self-assembly

Abstract

We developed a novel nano-capsule using the micellization ability of α-lipoic acid for the purpose of stabilizing α-lipoic acid. α-Lipoic acid is an optically active substance consisting of a carboxyl group and a five-membered ring with a disulfide bond, functioning as a cofactor in multi-enzyme complexes. The disulfide bond in the five-membered ring is unstable and easily degraded by light or heat stress, resulting in the sulfurous smell that has often interfered with formulations, especially for cosmetics. It was found that the present encapsulation technology could drastically improve α-lipoic acid stability, that is, stabilize the unstable disulfide bond in α-lipoic acid by orienting the hydrophobic moiety of α-lipoic acid inside of the nano-capsule with an inorganic shell. The surface of the nano-capsule was covered by polyethylene chains and inorganic ions, forming a core-shell structure. Besides the nano-capsule showed mono-dispersity of the size distribution around 10 nm in diameter. This article reports on the formulation and the physicochemical properties of the nano-capsule of α-lipoic acid. © 2013 Nishiura H, et al.