Mesalamine-loaded mucoadhesive microsphere for colon drug delivery system: Effect of process variables and in vitro characterization

Objective: The main objective of this study is to formulate mucoadhesive microspheres for colon drug delivery with sodium alginate (ALG) core enriched with drug. Methods: The core microspheres of ALG were prepared by modified emulsification method followed by cross-linking with different concentration of CaCl 2 at different stirring speed with constant drug-to-polymer ratio (1: 3). The core microspheres were further coated with Eudragit S-100 using the solvent evaporation technique. Results: The microspheres (core and coated) were characterized by shape, size, surface morphology, size distribution, entrapment efficiency, and in vitro drug release studies. In vitro drug release showed that the optimized batch of core microsphere and coated microspheres exhibited 99.53% +/- 0.39% and 89.22% +/- 0.26%, respectively. The drug release from all formulations of mesalamine microsphere followed Higuchian Kinetics. Moreover, drug release from core and Eudragit S-100-coated microspheres followed Korsmeyer-Peppas equation with anomalous and Fickian kinetics mechanism, respectively. Stability study suggests that the degradation rate constant of mesalamine from Eudragit S-100-coated microsphere was found to be minimum 2 years shelf life of the formulation. On the basis of scanning electron microscopy, the core microspheres were formed slightly irregular in shape due to surface-attached crystals of the drug and coated mesalamine microspheres showed smooth surface and a smaller number of pores due to coating. Conclusions: It can be concluded that the appropriate combination of a pH-dependent polymer (Eudragit S-100) with a pH-independent polymer sodium ALG) was suitably adequately sustained the drug release from mesalamine microspheres.