Novel interpenetrating network chitosan-poly(ethylene oxide-g-acrylamide) hydrogel microspheres for the controlled release of capecitabine

This paper describes the synthesis of capecitabine-loaded semi-interpenetrating network hydrogel microspheres of chitosan-poly(ethylene oxide-g-acrylamide) by emulsion crosslinking using glutaraldehyde. Poly(ethylene oxide) was grafted with polyacrylamide by free radical polymerization using ceric ammonium nitrate as a redox initiator. Capecitabine, an anticancer drug, was successfully loaded into microspheres by changing experimental variables such as grafting ratio of the graft copolymer, ratio of the graft copolymer to chitosan, amount of crosslinking agent and percentage of drug loading in order to optimize process variables on drug encapsulation efficiency, release rates, size and morphology of the microspheres. A 2(4) full factorial design was employed to evaluate the combined effect of selected independent variables on percentage of drug release at 5 h (response). Regression models were used for the response and data were compared statistically using the analysis of variance (ANOVA). Grafting, interpenetrating network formation and chemical stability of the capecitabine after encapsulation into microspheres was confirmed by Fourier infrared spectra (FTIR). Differential scanning calorimetry (DSC) and X-ray diffractometry (XRD) studies were made on drug-loaded microspheres to investigate the crystalline nature of drug after encapsulation. Results indicated amorphous dispersion of capecitabine in the polymer matrix. Scanning electron microscope (SEM) confirmed spherical shapes and smooth surface morphology of the microspheres. Mean particle size of the microspheres as measured by the laser light scattering technique ranged between 82 and 168 mu m. Capecitabine was successfully encapsulated into semi-IPN microspheres and percentage of encapsulation efficiency varied from 79 to 87. In vitro release studies were performed in simulated gastric fluid (pH 1.2) for the initial 2 h, followed by simulated intestinal fluid (pH 7.4) until complete dissolution. The release of capecitabine was continued up to 10h. Release data were fitted to an empirical relationship to estimate the transport parameters. Dynamic swelling studies were performed in the simulated intestinal fluid and diffusion coefficients were calculated by considering the spherical geometry of the matrices. (c) 2006 Elsevier B.V. All rights reserved.