Encapsulation of α-lipoic acid into chitosan and alginate/gelatin hydrogel microparticles and its in vitro antioxidant activity

Alpha-lipoic acid is an organosulphur compound well-known for its therapeutic potential and antioxidant properties. However, the effective use of α-lipoic acid depends on biological plasma half-life and its preserving stability, which could be improved by encapsulation. In this study, α-lipoic acid was incorporated into chitosan microparticles obtained by reverse emulsion crosslinking technique, as well as into microparticles of alginate/gelatin crosslinked with zinc ions. Encapsulation of α-lipoic acid in both cases was carried out by swelling of synthesized dried microparticles by their dipping in a solution of the active substance under strictly controlled conditions. Encapsulation efficiency of α-lipoic acid obtained in this study was up to 53.9%. The structural interaction of α-lipoic acid with the carriers was revealed by Fourier transform infrared spectroscopy. In vitro released studies showed that controlled release of α-lipoic acid was achieved through its encapsulation into chitosan microparticles. The results of in vitro antioxidative activity assays of released α-lipoic acid indicated that antioxidant activity was preserved at a satisfactory level. These obtained results suggested that chitosan microparticles could be suitable for modeling the controlled release of α-lipoic acid.