The effect of charges on the corneal penetration of solid lipid nanoparticles loaded Econazole after topical administration in rabbits

Fungal keratitis is an infectious disease caused by pathogenic fungi with a high blindness rate. Econazole (ECZ) is an imidazole antifungal drug with insoluble ability. Econazole-loaded solid lipid nanoparticles (E-SLNs) were prepared by microemulsion method, then modified with positive and negative charge. The mean diameter of cationic E-SLNs, nearly neutral E-SLNs and anionic E-SLNs were 18.73 & PLUSMN;0.14, 19.05 & PLUSMN;0.28, 18.54 & PLUSMN;0.10 nm respectively. The Zeta potential of these different charged SLNs formulations were 19.13 & PLUSMN;0.89, -2.20 & PLUSMN;0.10,-27.40 & PLUSMN;0.67 mV respectively. The Polydispersity Index (PDI) of these three kinds of nanoparticles were all about 0.2. The Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) analysis showed that the nanoparticles were a homogeneous system. Compared with Econazole suspension (E-Susp), SLNs exhibited sustained release capability, stronger corneal penetration and enhanced inhibition of pathogenic fungi without irritation. The antifungal ability was further improved after cationic charge modification compared with E-SLNs. Studies on pharmacokinetics showed that the order of the AUC and t1/2 of different preparations was cationic E-SLNs > nearly neutral E-SLNs > anionic E-SLNs > E-Susp in cornea and aqueous humor. It was shown that SLNs could increase corneal penetrability and ocular bioavailability while these capabilities were further enhanced with positive charge modification compared with negative charge ones.