Design and optimization of thermosensitive nanoemulsion hydrogel for sustained-release of praziquantel

Objective: This work aimed to develop an alternative sustained-release thermosensitive praziquantelloaded nanoemulsion (PZQ-NE) hydrogel for better schistosomiasis treatment. Significance: PZQ-NE-dispersed chitosan/glycerol 2-phosphate disodium/HPMC (NE/CS/beta-GP/HMPC) hydrogel was successfully prepared to improve bioavailability of PZQ. Methods: Solubility tests and pseudo-ternary phase diagrams were applied to screen optimal oils, surfactants and co-surfactants of NE. The hydrogels were characterized for gelling time, surface exudates, rheological properties and in vitro drug release. Formulation optimization of NE/CS/beta-GP/HMPC hydrogel was conducted by Box-Behnken experimental design combined with response surface methodology. In vitro cytotoxicity of hydrogel was studied by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide method. The sustained-release property of PZQ in NE and optimized hydrogel was evaluated by pharmacokinetic study in rabbits. Results: The formulation of PZQ-NE consisted of mass ratio of 12.5% capryol 90 containing PZQ (160mg/g), 40% cremophor RH 40/tween 20 and transcutol HP (S/CoS = 2: 1), 47.5% deionized water. PZQ releasing from NE/CS/beta-GP/HMPC hydrogels was best fitted to Higuchi model and governed by diffusion. Rheological investigation evidenced the themosensitive gelation of different hydrogel systems and their gel-like character at 37 degrees C. The optimized hydrogel formulation consisted of HPMC solution (103.69mg/g), 3.03% (w/v) chitosan and 14.1% (w/v) beta-GP showed no cytotoxicity when the addition of NE was no more than 100mg/g. Pharmacokinetic parameters indicated that NE/CS/beta-GP/HMPC hydrogel can significantly slow down drug elimination, prolong mean residence time and improve bioavailability of PZQ. Conclusions: NE/CS/beta-GP/HMPC hydrogel possessed sustained-release property and could be an alternative antischistosomal drug delivery system with improved therapeutic effect.