Chitosan oleate-tripolyphosphate complex-coated calcium alginate bead: Physicochemical aspects of concurrent core-coat formation

This study designed chitosan species-coated calcium alginate beads through concurrent core-coat formation. Chitosan oleate was synthesized by carbodiimide chemistry and characterized by ¹H NMR and FTIR techniques. Chitosan or chitosan oleate was coated onto the forming alginate or alginate/tripolyphosphate core using vibratory nozzle extrusion-microencapsulation approach, followed by calcium crosslinking. Chlorpheniramine maleate served as a model water-soluble drug. The molecular characteristics, size, shape, morphology, swelling, erosion, water uptake, drug content and drug release profiles of beads were evaluated. Discrete spherical coated beads were obtained through minimizing successive bead adhesion through an interplay of nozzle vibrational frequency and polymeric solution flow rate. The tripolyphosphate ions in the core possessed higher diffusional kinetics than alginate and were better able to attract chitosan species onto bead surfaces to facilitate alginate-chitosan coacervation. Amphiphilic chitosan oleate formed smaller aggregates than chitosan. It interacted with greater ease with core alginate and tripolyphosphate. The gain in alginate/tripolyphosphate interaction with chitosan oleate at the core-coat interface enhanced bead robustness against swelling and water uptake with drug release consequently dependent on the loss of alginate-drug interaction.