Dexamethasone-Loaded Chitosan Beads Coated with a pH-Dependent Interpolymer Complex for Colon-Specific Drug Delivery

Abstract

Chitosan (CS) microparticles loaded with dexamethasone were prepared by spray drying, followed by coating with a pH-dependent interpolymer complex based on poly(acrylic acid)/poly(vinyl pyrrolidone) using an water-in-oil emulsion technique. The aim of this research was to evaluate the influence of PAA/PVP coating on the release of dexamethasone from loaded chitosan microparticles, in simulated gastric fluid (SGF, pH=1.2) and simulated intestinal fluid (SIF, pH=6.8). The release of dexamethasone from uncoated loaded CS microparticles was similar in both fluids, and almost complete release of the drug was achieved in 5 hours. In the coated loaded CS microparticles, the release of dexamethasone in SGF was reduced considerably, very close to zero, due to the interpolymer complex formation at low pH, demonstrating that this system applied as pH-dependent coating has a potential as a site-specific delivery system.