Development of a pH-responsive gellan gum /sodium polyaspartate/chitosan hydrogel for delivery of coumarin-6 via chitosan-g-oleic acid micelles

The hydrophobic model drug coumarin-6 was encapsulated into chitosan-grafted oleic acid micelles and subsequently incorporated into a hydrogel composed of gellan gum, sodium polyaspartate, and chitosan. The hydrogel was synthesized via ionic interactions using the semi-dissolution/acidification/sol–gel transition method. The C6-loaded micelles exhibited a spherical morphology with an average particle size of 310 nm and an encapsulation efficiency of 29%. Upon freeze-drying, the hydrogel showed an average pore size of approximately 300 µm, which decreased slightly when treated at pH 1, 4, and 8 (280, 240, and 230 µm, respectively). The hydrogel also demonstrated an excellent water absorption capacity, ranging from 695% to 1303% across a broad pH range (1-8). The encapsulation efficiency of coumarin-6 in the hydrogel reached was 37.7%. Given its pH responsiveness, structural stability, and ability to encapsulate hydrophobic drugs, the GG/NaPASP/CS micelle-hydrogel platform shows strong potential for oral drug delivery and gastrointestinal-targeted release applications.