Development and evaluation of pH-sensitive sodium alginate/chitosan microparticles containing the antituberculosis drug rifampicin

This paper describes the encapsulation of a high molecular weight molecule rifampicin (RIF) in sodium alginate/chitosan microparticles, which provided controlled-release when evaluated in vitro. The microparticles were prepared by the coacervation technique. To evaluate and select the best encapsulation method two approaches were applied: coacervation (MCP method 1) and impregnation (MCP method 2). The microparticles obtained were analyzed by DSC, DRIFT, XRD and SEM and also the loading efficiency, swelling degree (SD) and in vitro release were determined. The results obtained showed that the alginate/chitosan microparticles represent an efficient system for the controlled-release of RIF. At acidic pH, the release of 20% of the drug occurred in 2 h, and at pH 6.8 a rapid increase in the release rate was observed up to 100%. The mechanism involved in the release was Super Case II kinetics since n > 1 (n = 1.09 and 1.13 for microparticles produced by methods 1 and 2, respectively), indicating that the release was related to diffusion, swelling, relaxation and erosion processes. The dissolution efficiencies were similar for both formulations, and the f2 values of ≥ 50 indicated the similarity between the two profiles, under the assumption of a maximum allowable difference of 10%.