Chitosan microspheres for encapsulation of α-lipoic acid

Encapsulation of α-lipoic acid (LA) was carried out using chitosan as an encapsulant matrix. Placebo and LA-loaded chitosan microspheres were prepared by a spray-drying process. Scanning electron microscopy (SEM) studies confirmed the spherical particle geometry and the smooth surface morphology of LA-loaded particles. The particle size distribution (PSD) analysis of the placebo and LA-loaded microspheres has shown that 50% of the microspheres were less than 3.53 and 7.89 μm, respectively. The structural interactions of the chitosan matrix with the encapsulated LA were studied by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) which revealed structural interactions of lipoic acid with the encapsulant matrix. The antioxidant activity of encapsulated lipoic acid was studied using the free-radical scavenging assay. This study demonstrated significant retention of antioxidant activity of lipoic acid (75%) after encapsulation in the chitosan matrix. Encapsulation efficiency of lipoic acid obtained in this study was 55.2% when ethanol and acetic acid (1:1 v/v) was used as incubation/extraction medium.