Abstract
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 invitro 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 thephysicochemical 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 beadsin 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 thedrug 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 inthe bead formulations
Highlights
Alginate is a natural biopolymer which forms a hydrogel in the presence of divalent cations such as Ca2+ [1]
Much attention has been given in recent years to the use of chitosanalginate polyelectrolyte complex in controlled drug delivery [3]
Nimodipine is a suitable candidate for oral sustained release drug delivery
Summary
Alginate is a natural biopolymer which forms a hydrogel in the presence of divalent cations such as Ca2+ [1]. The inert environment within the biopolymer network of alginates allows for the entrapment of a wide range of substances [2]. The use of chitosan has been reported in the literature for coating alginate beads in order to alter the diffusion rate of the encapsulated substances and as an additive for the bulk modification of the bead structure [4]. Nimodipine (NM) is isopropyl-2-methoxyethyl1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5 -pyridine dicarboxylate, a dihydropyridine calcium antagonist. It has a short half-life of 1-2 h, and the usual oral dose is 30 to 60 mg to be taken 2 to 4 times a day. The physical state of the drug in the beads and its swelling behavior in the bead formulation were assessed
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