Release behavior of microspheres from cross-linked N-methylated chitosan encapsulated ofloxacin

A series of hollow microspheres encapsulated with ofloxacin have been successfully prepared, using cyclohexane droplets as a template and the N-methylated chitosan (NMC) cross-linked with glutaraldehyde as the shell. The structure and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The swelling and releasing behaviors of the microspheres having different weight-average molecular weights (Mw) and the degree of quaternization of NMC at pH 1.2 and 7.4 media were investigated. The results revealed that microspheres exhibited a very smooth surface, and electrostatic interaction existed between cross-linked NMC and ofloxacin. Ofloxacin encapsulated in the microspheres was rapidly released into phosphate buffer solution (pH 7.4), whereas it was only slowly released in 0.1 M HCl (pH 1.2). The degree of swelling of microspheres at pH 7.4 was higher than that at pH 1.2. Moreover, ofloxacin was released more slowly from the microspheres having high Mw of NMC than that with low Mw. The release mechanism of the hollow microsphere was proposed to be a non-Fickan diffusion through the swollen microspheres, and to be controlled by the Mw and the cross-linking density of shell.