Incorporating inulin and chitosan in alginate-based microspheres for targeted delivery and release of quercetin to colon

Colon targeted delivery of quercetin by encapsulation has the potential to manage colonic diseases due to quercetin’s pharmacological effects. To strengthen the functionalities of commonly used alginate microspheres for quercetin encapsulation, inulin was added as filling material and chitosan as coating material. Empty/quercetin-loaded alginate (AL-E/Q), alginate + inulin (ALIN-E/Q), alginate + inulin + chitosan (ALINCH-E/Q) microspheres were fabricated, with particle sizes ranging from 25.1 ± 1.8 to 79.4 ± 4.5 µm. All the formulated microspheres were negatively charged, and zeta potential was dependent mainly on chitosan coating and the pH of surrounding media. FTIR spectra of the microspheres suggested successful encapsulation of quercetin, formation of chitosan coating and potential hydrogen bonding between inulin and alginate. Scanning electron micrographs showed that inulin filling enhanced gel strength by filling up the pores in the alginate polymer network, and that loading of quercetin also helped to fill up the pores compared to empty microspheres. Combination of inulin as filling material and chitosan as coating material in quercetin loaded ALINCH-Q achieved superior performance compared to other formulations with encapsulation efficiency of 53.2 ± 1.2 %, and retention rate of the loaded quercetin up to 80.3 ± 4.4 % through in vitro gastrointestinal digestion, thus was chosen for colonic fermentation. Subjecting ALINCH-Q to colonic fermentation using pig fecal material as microbiota source showed that quercetin release was delayed but occurred within 3 h of fermentation and was completely metabolized by the microbiota by 24 h. Thus, ALINCH-Q microsphere showed potential in targeted delivery and release of quercetin to the colon.