| Objective:Praziquantel (PZQ) is the first choice drug against schistosomiasis, which is the only one that is effective to five human schistosomiasis infection currently. However the strong first pass effect of the compound, inactive metabolites, low bioavailability, large oral dose and strong injection stimulus has severely limited its pharmacodynamics and application. The purpose of this article is to prepare praziquantel long circulating nanoparticles, which can prolong the circulation time of drug in vivo and improve drug concentration, and establish quality evaluation methods.pharmacokinetics behavior in rabbits was investigated to build a foundation for the research of new agents to improve the efficacy of PZQ. Methods and Results:PZQ long circulation nanoparticle was prepared by emulsification-ultrasonic dispersion method, and evaluated by appearance, particle size, encapsulation efficiency and stability. Single factor study and orthogonal test was carried to study prescription and technology process respectively, the optimal prescription was as follows:main drug (60 mg), glyceryl behenate (0.3 g), glycerin monostearate (0.3 g), butyl acetate (0.3 g), DSPE-PEG2000 (0.2 g), lecithin (1.0 g), poloxamer 188 (0.8 g), sodium stearate (40 mg), H2O(20 mL); the best technology conditions were: hydrofacies (lecithin, poloxamer 188, sodium stearate, H2O) and oil phase(PZQ, glyceryl behenate, glycerin monostearate, butyl acetate) were dissolved respectively in water bath(70℃). After water phase was poured into oil phase, cutted in high speed (8000 rpm,10 min), given an ultrasonic (10 min), then PZQ long circulating nanoparticles was prepared by magnetic stirring and cooling.PZQ long circulating nanoparticles(LCN) was prepared on the basis of PZQ nanoparticle adding long circulation modified material DSPE-PEG2000, and investigated in different DSPE-PEG2000 dosage (0%,2.5%,5.0%,10.0%), and evaluated by particle size, surface charge, surface fixed aqueous layer thickness, encapsulation efficiency, release rate and cell phagocytic rate to optimize prescription.The PZQ-LCN prepared were kinds of transparent clear liquids with slightly opalescence when the DSPE-PEG2000 dosage was 0%,2.5%, 5.0%,10.0% respectively, particle size detected by nanoparticle size dynamic light scattering instrument were 95.57±1.27 nm,90.13±2.11 nm,94.91±3.19 nm,77.79±1.01 nm respectively, and decreased with the increasing of DSPE-PEG2000 dosage. Zeta potential detected by streaming potential methods were -50.3±1.1 mV,-49.4±1.2 mV,-47.9±1.2 mV,-40.3±1.4 mV respectively, and decreased with the increasing of DSPE-PEG2000 dosage. DSPE-PEG2000 can reduce the surface charge of nanoparticle. Surface fixed aqueous layer thickness counted in Gouy-Chapmann diffused double layer pattern were 1.56 nm±0.32 nm, 2.41±0.24 nm,4.97±0.16 nm,7.03±0.39 nm respectively, and increased with the increasing of DSPE-PEG2000 dosage. Encapsulation efficiency detected by Sephadex microcolumn centrifugation method and HPLC were 72.7%±2.7%,70.1%±3.1%,67.3%±0.9%,68.2%±3.5% respectively, and had little to do with DSPE-PEG2000 dosage. The release rate detected by dynamic dialysis method and HPLC were 77.7%±3.5%,82.1%±3.7%,83.1%±2.8%,87.4%±4.2% in 24 hours, and accelerated with the increasing of DSPE-PEG2000 dosage. When release curves fitted by the Ritger-Peppas pattern, r values were greater than 0.9, n are close to 0.5, indicating that the release of nanoparticles is mainly by diffusion mechanism. The hagocytic rate of LCN detected by phagocytosis pattern of macrophage in vitro and HPLC were 10.21%±2.85%,5.32%±1.93%,3.75%±1.31%,1.62%±0.41% respectively, and decreased with the increasing of DSPE-PEG2000 dosage. These suggest that particle size became smaller, Zeta potential decreased, surface fixed aqueous layer thickness increased, and cell phagocytic rate decreased when the DSPE-PEG2000 dosage in PZQ-LCN was at the range of 0-10%. So we chose 10% as the optimal prescription about DSPE-PEG2000 dosage.Pharmacokinetic parameter difference in PZQ solution, PZQ-SLN and PZQ-LCN were compared by the study of pharmacokinetic in rabbits.The rabbits were intravenously injected with PZQ solution, PZQ-SLN and PZQ-LCN (10 mg·kg-1) through the edge of the ear, then took blood from heart, the concentration were determined by HPLC,and main pharmacokinetic parameters were measured by DAS 2.0 software. Some pharmacokinetic parameters are as follow:t1/2were 1.27±1.56h, 1.13±0.66h,23.82±8.94 respectively; CL were 5.29±0.78L·h-1·kg-1, 2.38±1.00 L·h-1-kg-1,1.16±0.16L·h-1-kg-1 respectively; this indicated that t1/2 of LCN prolonged, CL of LCN decreased, comparing with SLN. AUCo-t were 1.48±0.27 mg·h·mL-1,3.52±1.79mg·h·mL-1,4.93±1.27 mg·h·mL-1 respectively; AUC0-∞were 1.93±0.276mg·h·mL-1,5.07±2.77mg·h·mL-1,8.79±1.21mg·h·mL-1 respectively; MRT were 0.44±0.30 h,0.41±0.10 h,16.12±1.38 h respectively; Effective blood concentration (0.3μg-mL-1) duration were 0.75 h,1 h,12 h respectively. Compared with the SLN, LCN PZQ significantly extended the residence time in vivo, indicating that DSPE-PEG2000 surface modified nanoparticles can prolong the duration of the effective blood concentration in vivo. Conclusion:The prescription Process of SLN optimized by orthogonal design formulation in this study, and small size, high encapsulation efficiency and good stability PZQ-SLN was prepared. On this basis, we investigated the impact of DSPE-PEG2000 dosage on the PZQ-LCN particle size, surface charge, encapsulation efficiency, surface fixed aqueous layer thickness, release rate, phagocytic rate and so on systematically, so as to lay the basis for preparation of the PZQ-LCN and provide a theoretical basis in vivo studies. Pharmacokinetic experiments show that the duration of effective blood concentration of PZQ-LCN in rabbits was 16 times of PZQ injection,12 times of PZQ-SLN. This study provide pharmacokinetic basis for the further pharmacodynamic research of PZQ-LCN, and also offers a new pharmaceutical idea to improve the clinical effect of PZQ.
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