Electrosprayed chitosan-coated alginate microspheres for ellagic acid/urolithins delivery: Characterization,...

Natural polysaccharides sodium alginate (SA) and chitosan (CS) were used to fabricate electrosprayed CS-coated SA microspheres (core-shell structured; blank ones denoted as MP) for encapsulating ellagic acid (EA) and urolithins (Uro A, Uro B, Uro C, Iso A), addressing EA's low bioavailability and urolithin metabolic variability. With 1% SA, all microspheres showed uniform size (< 100 μm), and the drug-loaded formulations achieved 60-88% encapsulation efficiency. FTIR confirmed successful drug embedding: SA (1613 cm^-1) and CS (1654 cm^-1) characteristic peaks changed vs. pure polysaccharides, and a faint, drug-specific peak at 1508 cm^-1 (only in drug-loaded microspheres) indicated the presence of non-covalent physical interactions between components. TGA/DTG showed enhanced thermal stability in drug-loaded microspheres: MP@EA had a higher Tₘ (261 °C) than MP (241 °C). Higher SA content (1% to 2.0%) reduced Tₘ (241 → 224 °C for MP; 261 → 246 °C for MP@EA), confirming drug-polymer interactions improved heat resistance. The antioxidant activity of all encapsulated drugs was reduced by approximately 25-45% compared with their corresponding free drugs, while in vitro digestion mitigated drug loss by 32-69% with intact structural integrity of the encapsulated system. Thus, CS-coated SA microspheres serve as an efficient polysaccharide carrier to protect bioactives during digestion, offering a novel strategy to address EA's low bioavailability and urolithin metabolic variability.