Effect of Solvent Type and Drying Method on Protein Retention in Chitosan-Alginate Microcapsules

Edith I Ahonkhai, Ikhuoria M Arhewoh and Augustine O Okhamafe

Department of Pharmaceutics and Pharmaceutical Technology, Faculty of Pharmacy, University of Benin, Benin City 300001, Nigeria

 

Tropical Journal of Pharmaceutical Research 2006; 5(2): 583-588

ISSN: 1596-599

 

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 λ_max 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 pK_a 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.