| Objective To detect the median lethal dose (LD50) for polylactic acid- polyglycolic acid copolymer-vincristine sulfate (PLGA-VCR) microspheres by different drugs delivery on Wistar rats, and disclose the plasma protein binding rate and anti-tumor targeting, then give an evaluation of antitumor targeting for the microspheres, provied the dose parameters for research in pharmacokinetics and pharmacodynamics, as well as lay the foundation for clinical research.Methods Firstly, Wistar rats were divided into three groups, detected the median lethal dose(LD50) for VCR and PLGA-VCR microspheres on different drug delivery by the modified method of Cole’s, and the results were compared with each other. Secondly, plasma protein binding rate was determined by equilibrium dialysis on Wistar rats, liquid-liquid extraction was used to purify drugs, and detected drug concentration by high performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS). Finally, BALB/c nude mices were divided into two groups, ectopic liver tumor models were established by subcutaneous injection of tumor cells, LC-MS was adopted to evaluate anti-tumor targeting for PLGA-VCR microspheres and VCR.Results①The dose of LD50 of VCR in rats was 1.48mg·kg-1 via intravenous injection and the 95% confidence interval was 1.36-1.61mg·kg-1. The dose of LD50 of PLGA-VCR microspheres in rats was 3.83mg·kg-1 via intravenous injection and the 95% confidence interval was 2.86-5.13mg·kg-1, and the dose of LD50 of PLGA-VCR microspheres in rats was 4.33mg·kg-1 via intraperitoneal injection and the 95% confidence interval was 3.49-5.38mg·kg-1.②HPLC detected the concentration of PLGA-VCR in both sides of dialysis bags reached the best balance at the point of 120 hours, the protein binding rate was 35.91% ,40.01% ,35.79% ,32.55% , 39.24% ,41.34% when the concentration of plasma PLGA-VCR was 2.50,5.00,10.00,20.00, 40.00, and 80.00μg-ml-1 respectively. As well as, LC-MS detected the concentration of PLGA-VCR in both sides of dialysis bags reached the best balance at the point of 120 hours, the protein binding rate was 20.70%、27.33%、29.70%、39.28%、42.93%, when the concentration of plasma PLGA-VCR was 10.0、20.0、40.0、80.0、160.0 ng·ml-1 respectively.③Compared with VCR, the relative uptake rate of PLGA-VCR was 3.8,4.5,6.8,4.9,4.8,5.9,6.8,6.3,6.9,6.1,5.7, the peak concentration ratio of PLGA-VCR was 1.9,1.7,1.8,1.7,1.8,1.7,2.1,1.6,1.8,2.3,1.2, in heart, lung, liver, kidney, spleen, brain, gastrointestinal tract, fat, gonads, skeletal muscle and tumor tissues, respectively. Compared with the drugs targeting in heart, lung, liver, kidney, spleen, brain, gastrointestinal tract, fat, gonads, skeletal muscle, the targeting efficiency of PLGA-VCR in the tumor tissue was 1.2,1.0,0.7,1.7,0.8,2.0,0.8,2.1,3.0,1.1, the targeting efficiency of VCR was 0.8,0.8,0.8,1.5,0.7,2.1,0.9,2.3,3.7,1.2 respectively.Conclusion PLGA-VCR microspheres with good slow-release effect, which can reduce the burst release of drug induced acute toxicity, at the same time, the release process extend will reduce the risk of chronic toxicity. Because of the slow degradation of PLGA, VCR shows long-term release which is wrapped in the microspheres, while, the absorption and release rate of VCR is different in microspheres, resulting in the initial plasma protein binding rate have greater fluctuation, but with time extend, the plasma protein binding rate can reach a stable level. The experimental results demonstrate that PLGA-VCR is not concentration-dependent in the range from 2.50 to 80.00 ug·ml-1, and in the range from 10.0 to 160.0 ng·ml-1,which is concentration- dependent; Compared with the VCR, PLGA-VCR has good relative uptake rate and peak concentration ratio, the results descript PLGA-VCR has a higher targeting and the effect of changing the distribution of drug in vivo than VCR, but the PLGA-VCR and the VCR in the targeting efficiency of hepatic tumor tissue not have significant difference. |
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