| Objective: Paclitaxel nanocrystals（PNCs）,a novel drug delivery system,were prepared by using paclitaxel（PTX）as a model drug.In this study,PNCs were modified with DSPE-PEG2000 to improve its transport behavior in blood circulation,and to evaluate the long circulation effect of DSPE-PEG2000.Methods: An anti-solvent precipitation method was used to prepare PNCs and PNCs modified with DSPE-PEG2000（DSPE-PEG-PNCs）.The appearance and average particle size were used as the main evaluation indexes.The effects of stirring speed,mixing time,ultrasonic power and time,and injection rate of organic phase on the particle size were investigated by single factor experiment,also the effects of different organic solvents,the ratio of PTX to PVA,drug concentration and volume ratio of organic phase to aqueous phase on particle size were determined in order to determine optimum technological conditions and optimal prescription;The binding efficiency of DSPE-PEG2000 to PNCs surface was determined by fluorescence quantification;The physical characterization of nanocrystals was carried out by dynamic light scattering（DLS）and transmission electron microscope（TEM）,so the particle average size and morphology were determined;A method to measure the concentration of PTX was established to compare the in vitro release characteristics of PNCs and DSPE-PEG-PNCs.In addition,the methodology of LC-MS/MS was established to determine the concentration of PTX in vivo.The pharmacokinetics of PNCs and DSPE-PEG-PNCs were explored to evaluate the pharmacokinetic characteristics.Results: The optimum technological conditions were determined by single factor experiment,when stirring speed was 300 rpm/min,the mixing time was 5 min,the ultrasonic power was 300 W,the ultrasonic time was 10 min and the injection rate of organic phase was 4 m L/min,also the formulation was composed of PTX,PVA and DSPE-PEG2000,the optimal prescription was determined that organic solvent was ethanol,the ratio of PTX to PVA was 1:5and volume ratio of organic phase to water phase was 1: 20,the prepared PNCs had the advantages of uniform stability and good dispersion;The binding efficiency of DSPE-PEG2000 to PNCs surface was 0.4%;The characterization results showed that the distribution of PNCs is uniform and the potential is stable.The average particle size of PNCs was 178.9±3.4 nm,PDI was 0.129 and the potential value was-11.5±0.4 mv.The average particle size and PDI of DSPE-PEG-PNCs were 160.6±2.3 nm and 0.11,and potential value was-18.9±0.3 mv,respectively.Compared with the PNCs,the negative electrical properties were enhanced,and the particle size and PDI of DSPE-PEG-PNCs were decreased slightly,but size distribution of PNCs and DSPE-PEG-PNCs was similar nearly;The results of transmission electron microscopy（TEM）showed that the surface of PNCs was smooth,and it suggested that the morphology of PNCs did not change obviously by surface functionalization;The in vitro release rate of DSPE-PEG-PNCs was significantly slower than that of PNCs.It showed that sustained in vitro release of PTX from DSPE-PEG-PNCs;According to results of pharmacokinetic,the drug concentration of DSPE-PEG-PNCs was significantly higher than that of PNCs,and DSPE-PEG-PNCs presented higher area under curve（AUC）and lower clearance rate（CL）,the AUC of DSPE-PEG-PNC（4.430±0.190 mg/L*h）was higher than PNCs（2.484±0.183 mg/L*h）.These results indicated that DSPE-PEG-PNCs might serve as a potential sustained release system for poorly water-soluble agents.Conclusions: The PNCs prepared by an anti-solvent method were uniform and stable,and the in vitro release rate of DSPE-PEG-PNCs was obviously decreased;The pharmacokinetic results also demonstrated that DSPE-PEG-PNCs could prolong the systemic circulation of PTX in blood.In conclusion,DSPE-PEG2000 had a long circulation effect and it had great potential for PNCs to be used in clinical therapy and had clinical significance. |
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