Preparation, optimization, and characterization of chitosan-coated solid lipid nanoparticles for ocular drug delivery

The present study aimed to develop and optimize chitosan coated solid lipid nanoparticles (chitosan-SLNs) encapsulated with methazolamide. Chitosan-SLNs were successfully prepared by a modified oil-in-water emulsification-solvent evaporation method with glyceryl monostearate as the solid lipid and phospholipid as the surfactant. Systematic screening of formulation factors was carried out. The optimized formula for preparation was screened by orthogonal design as well as Box-Behnken design with entrapment efficiency, particle size and zeta potential as the indexes. The entrapment efficiency of the optimized formulation (methazolamide-chitosan-SLNs) prepared was (58.5 +/- 4.5)%, particle size (247.7 +/- 17.3) nm and zeta potential (33.5 +/- 3.9) mV. Transmission electron microscopy showed homogeneous spherical particles in the nanometer range. A prolonged methazolamide in vitro release profile was obtained in the optimized chitosan-SLNs suspension compared with methazolamide solution. No ocular damages were observed in the susceptibility test on albino rabbits. The results suggest that the combination of orthogonal design and Box-Behnken design is efficient and reliable in the optimization of nanocarriers, and chitosan-SLNs is a potential carrier for ophthalmic administration.