New bilayer-coated microbead system for controlled release of 5-aminosalicylic acid

A new bilayer-coated microbeads for oral delivery of 5-aminosalicylic acid (5-ASA) were prepared from naturally occurring polysaccharides via emulsification method. 5-ASA was successfully encapsulated in chitosan-lambda-carrageenan-coated alginate microbeads. The morphology and sizes of microparticles were studied using optical microscopy and dynamic light scattering. Drug release profiles were followed using high-performance liquid chromatography (HPLC) with spectrophotometric detection. The effect of chitosan thin layer and chitosan-lambda-carrageenan bilayer on the drug release was studied at pH values simulating these characteristic for stomach (pH = 1.2) and intestine (pH = 7.4). Chitosan layer slightly increased 5-ASA release at pH = 1.2, whereas double-layer external coating decreased the release rates. Due to the bilayer properties, the micro-carriers were additionally protected against acidic conditions of the stomach and drug release in the intestine could be better controlled.