Preparation and in vitro evaluation of amoxicillin encapsulated in alginate-coated chitosan microparticles

Purpose: To optimize and characterize amoxicillin encapsulated in mucoadhesive alginate-coated chitosan microparticles for the treatment of gastric and duodenal ulcers caused by Helicobacter pylori. Methods: Eighteen batches of various ratios of chitosan, sodium alginate and calcium chloride were prepared by ionotropic gelation method. The batches were optimized based on their particle size (PS) and drug encapsulation efficiency (PDEE). Optimized batches were further evaluated for in vitro drug release, bacterial susceptibility and mucoadhesion. Results: Microparticle size ranged from 0.70 +/- 0.37 to 5.25 +/- 0.70 mu m. Drug encapsulation efficiency ranged from 95.79 to 97.42 % while maximum drug released after 24 h was 44.79 % in simulated gastric fluid (SGF). Mucoadhesion reached a maximum of 76 % in simulated intestinal fluid (SIF). Drug release followed Higuchi model of release kinetics while the release exponent, n, was > 0.9 in all the formulations. There was a significant difference between the inhibition zone diameter (IZD) of the optimized formulations and that of a commercial brand of amoxicillin when they were tested against Salmonella typhi and Staphylococcus aureus. Conclusion: The mucoadhesive amoxicillin microparticles may improve the treatment of gastric ulcer caused by H. pylori due to enhanced adhesion of the formulation to the pig's ileum and the increased antibacterial property against Salmonella typhi and Staphylococcus aureus.