Sustained release of α-lipoic acid from chitosan microbeads synthetized by inverse emulsion method

The aim of this study was to investigate the encapsulation of α-lipoic acid (LA) onto chitosan microbeads in order to achieve a sustained release. Microbeads of different compositions were synthetized by inverse emulsion method, and characterized by in vitro swelling and drug release studies, FT-IR, DSC and SEM analyses. The encapsulation of LA was performed by swelling of previously synthetized dry microbeads in LA solution. The encapsulation efficiency was determined in terms of LA concentration, using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The swelling of synthetized microbeads was well pronounced in the acidic media. FT-IR analysis confirmed the presence of LA in microbeads and its interactions with matrices, which was in agreement with the results revealed by DSC analysis. SEM analysis revealed the porous structure, micron-size and spherical shape of the synthetized beads. Encapsulation efficiency was in the range from 46.8 to 58.5% depending on the hydrogel composition. The microbeads exhibited sustained release of LA under conditions mimicking gastrointestinal tract. Results of antioxidant activity of released LA showed good correlation with the concentration of the released LA. The obtained results suggested that synthetized microbeads have promising potential for oral administration with reduced dosing frequency in comparison to the immediate release formulations.