Alginate-Chitosan Particulate System for Sustained Release of Nimodipine

Purpose: The aim of this work was to prepare nimodipine-loaded alginate-chitosan beads for sustained drug release.
Methods: Nimodipine-loaded alginate-chitosan beads were prepared by ionic gelation method using various combinations of chitosan and Ca²⁺ as cations and alginate as anion. The swelling ability and in vitro drug release characteristics of the beads were studied at pH 1.2 and 6.8. Infra-red (IR) spectrometry, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), x-ray diffraction (XRD), and atomic absorption spectroscopy (AAS) were also applied to investigate the physicochemical characteristics of the drug in bead formulations.
Results: The surface morphology, size, and drug loading of the beads varied with increase in the concentration of chitosan and calcium chloride in the gelation medium. The swelling ability of the beads in different pH media was dependent on the presence of a polyelectrolyte complex in the beads and the pH of the media. Both calcium alginate beads and the beads treated with chitosan failed to release the drug at pH 1.2 over the period of study. On the other hand, at pH 6.8, calcium alginate beads released approx. 96 % of drug in 6 h, but treatment of the beads with chitosan lowered drug release to 73 %. Drug release mechanism was either "anomalous transport" or "case-II transport". Data from characterisation studies indicate that there was no significant change in the physical state of the drug in the bead formulations.
Conclusion: Although nimodipine-loaded alginate beads showed poor sustained release characteristics, modification with chitosan yielded beads that exhibited sustained drug release.

Keywords
Alginate-chitosan beads; Nimodipine; Swelling; Physicochemical characterization; Sustained release.