Preparation and in-vitro evaluation of single and bi-layered beeswax-based microparticles for colon-specific delivery of mesalamine

Abstract

Beeswax is selected as a natural coating material for the development of new colon specific drug delivery systems charged by mesalamine. In a first step, beeswax microparticles are prepared using hot-melt process of micro-encapsulation where drug:beeswax ratio, stirring speed, emulsifier concentration and pH of external phase are varied for the optimization of the drug entrapment and microparticles’ morphology. The effect of the nature of the emulsifier is also discussed by studying the hydrophilic–lipophilic balance (HLB) value. In a second step, to obtain delayed delivery systems, bi-layered microspheres are elaborated by the process of emulsion–solvent evaporation using ethylcellulose or cellulose acetate butyrate as outer enteric coating layer. All formulations are characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy and optical microscopy. The drug release is established in simulated gastric, small bowel and colon liquids and the release mechanism is discussed by applying the Korsmeyer–Peppas model.