Dual cross-linked chitosan microspheres formulated with spray-drying technique for the sustained release of levofloxacin.

This study was aimed to develop sustained drug release from levofloxacin (LF)-loaded chitosan (CS) microspheres for treating ophthalmic infections. Dual cross-linked CS microspheres developed by the spray-drying technique displays significantly higher level of sustained drug release compared with non-cross-linked CS microspheres. LF-loaded CS microspheres were prepared using the spray-drying technique, and then solidified with tripolyphosphate and glutaraldehyde as dual cross-linking agents. The microspheres were characterized by surface morphology, size distribution, zeta potential, encapsulation efficiency, and drug release profiles in vitro. The drug quantification was verified and analyzed by high-performance liquid chromatography (HPLC). The structural interactions of the CS with LF were studied with Fourier transform infrared spectroscopy. The effect of various influencing excipients in the formulation of the dual cross-linked CS microspheres on drug encapsulation efficiency and the drug release profiles were extensively investigated. The microspheres demonstrated high encapsulation efficiency (72.4 ∼ 98.55%) and were uniformly spherical with wrinkled surface. The mean particle size was between 1020.7 ± 101.9 and 2381.2 ± 101.6 nm. All microspheres were positively charged (zeta potential ranged from 31.1 ± 1.32 to 42.81 ± 1.55 mV). The in vitro release profiles showed a sustained release of the drug and it was remarkably influenced by the cross-linking process. This novel spray-drying technique we have developed is suitable for manufacturing LF-loaded CS microspheres, and thus could serve as a potential platform for sustained drug release for effective therapeutic application in ocular infections.