Methazolamide-loaded solid lipid nanoparticles modified with low-molecular weight chitosan for the treatment of glaucoma: vitro and vivo study

The aims of this study were to design and characterize methazolamide (MTZ)-loaded solid lipid nanoparticles (SLN) with and without modification of low molecular weight chitosan (CS) and compare their potentials for ocular drug delivery. Low molecular weight CS was obtained via a modified chemical oxidative degradation method. SLN with CS (CS-SLN-MTZ) and without CS (SLN-MTZ) were prepared according to a modified emulsion-solvent evaporation method. SLN-MTZ and CS-SLN-MTZ were 199.4 +/- 2.8 nm and 252.8 +/- 4.0 nm in particle size, -21.3 +/- 1.9 mV and +31.3 +/- 1.7 mV in zeta potential, respectively. Physical stability studies demonstrated that CS-SLN-MTZ remained stable for at least 4 months at 4 degrees C, while SLN-MTZ no more than 2 months. A prolonged in vitro release profile of MTZ from CS-SLN-MTZ was obtained compared with SLN-MTZ. Furthermore, CS-SLN-MTZ presented a better permeation property in excised rabbit cornea. In vivo studies indicated that the intraocular pressure lowering effect of CS-SLN-MTZ (245.75 +/- 18.31 mmHg x h) was significantly better than both SLN-MTZ (126.74 +/- 17.73 mmHg x h) and commercial product Brinzolamide Eye Drops AZOPT (R) (171.17 +/- 16.45 mmHg x h). The maximum percentage decrease in IOP of CS-SLN-MTZ (42.78 +/- 7.71%) was higher than SLN-MTZ (27.82 +/- 4.15%) and was comparable to AZOPT (38.06 +/- 1.25%). CS-SLN-MTZ showed no sign of ocular irritancy according to the Draize method and the histological examination.