Abstract
Purpose: The effect of solvent used in dissolving chitosan (membrane material) and the microcapsule drying method used, on protein retention in chitosan-alginate microcapsules were studied since these factors affect the physicochemical characteristics of the coating membrane. Method: The microcapsules were prepared by extruding a solution containing alginate and BSA into chitosan/calcium chloride solution prepared with different acid solvents – acetic acid, formic acid, tartaric acid and hydrochloric acid. A portion of the microcapsules was air-dried at ambient temperature while the remaining portion was freeze-dried. The elution of protein from the microcapsules in simulated gastric fluid was monitored spectrophotometrically at λmax 280 nm. Results: Tartaric acid effected the highest mean protein retention (54%) after 9 h followed by acetic acid (35%), hydrochloric acid (31%) and formic acid, (30%). There appears to be a link between the pKa of the acids and the degree of chitosan–solvent interaction on the one hand, and protein retention on the other hand. Increase in elution pH from 1.2 to 5.0 did not significantly (P>0.05) affect protein retention. Furthermore, there was no significant difference (p>0.05) between the protein retention capacities of air-dried and freeze-dried microcapsules as both types showed protein retention of 50% after 5 h. Conclusion: Tartaric acid was the most suitable solvent for enhancing protein retention in chitosan-alginate microcapsules in simulated gastric fluid . Keywords: Tartaric acid, chitosan, solvent type, microcapsules, air-drying, freeze-drying.> Tropical Journal of Pharmaceutical Research Vol. 5 (2) 2006: pp. 583-588
Highlights
Membrane coating is applied to solid dosage forms for a variety of reasons, including aesthetics 1, protection of drug from acid and enzymes in the gut 2, and environmental degradation 3, controlled drug release and sitespecific delivery 4
At pH 1.2, mean protein retention in microcapsules prepared with tartaric acid solution was 54% after 9 h compared to 35% for acetic acid, 31% for hydrochloric acid and 30% for formic acid over the same period
The effect of tartaric acid used in preparing chitosan solution on protein retention was found to be significantly different (p
Summary
Membrane coating is applied to solid dosage forms for a variety of reasons, including aesthetics 1, protection of drug from acid and enzymes in the gut 2, and environmental degradation 3, controlled drug release and sitespecific delivery 4. The choice of solvent in the preparation of coating solution is of particular importance because it affects the physicochemical characteristics of the encapsulating membrane and the final drug product Polymer membrane parameters such as permeability, solubility and stability 3 as well as microcapsule properties such as size, swelling and drug release profile 5 have been reported to be influenced by the nature of the solvent used. Cheap and has antifungal and bacteriostatic properties Because it is biodegradable, biocompatible and has great ease of chemical modification[7], it has found a wide range of applications in pharmacy and medicine such as inhibition of tumor cells, acceleration of wound healing and reduction of blood cholesterol level[8]. Acetic acid and to a lesser extent, formic acid, are often commonly used for preparing chitosan solutions for encapsulation processes[5,6,7]
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