| The paclitaxel which extracts from yews is a highly effective anti-cancer natural medication. It is the forefront medication for chemotherapy for treating cancer. The paclitaxel has a poor water-solubility, so people use solid lipid nanoparticle which has a good biological compatibility and can be biologically degraded to solve the paclitaxel deliquescent problem. The research shows that the PEG which covered with appearance of the lipid substance can extend the the blood half-life time and increase the microvascular infiltrating of the tumor. At domestic and abroad,Much research have utilized the covalence between folate and chemical agent or biological agent. in vivo and vitro experiment verificate that they can significantly increase to deliver medicine for masculine of the folate receptor. PEG is the bridge of it, which connect the folic acid with the lipid substance. It can improve the target of the medication, and at the same time, it also can improve the half life of the blood in the medication of lipid substance.Purpose: Synthesizing FA-PEG-DSPE, a new pattern Folate-mediated tumor cell targeting of liposome-entrapped paclitaxel was obtained. To study the pharmacal physico-chemical property of liposome drug and cell-growth inhibitory effect on KB cell, we use radioisotope 125I labeling paclitaxel directly, accordingly, providing qualified tracer agent for new nanometer paclitaxel, by which drug disposition and metabolism dynamics in vivo can be studied.Methods:FA-PEG-DSPE was synthesized via acylation reactivity at room temperature. Folate-mediated tumor cell targeting of nanoparticle liposome-entrapped paclitaxel was prepared by high pressure galactequal and galact equal method;The diameter and distributing of nanoparticle were detected by LASER particle diameter meter. Under the new type Folate-mediated tumor cell targeting of nanometer liposome-entrapped paclitaxel (TAX-NLC-FA)effected on KB cells, the growth inhibiting was studied by MTT. The Oxidants of 125I labeling paclitaxel were Ch-T,HNO3.The product was identified by thin paper chromatography and infrared spectrometry(IR).Results1. Synthesising FA-PEG-NH2 , with DCC or/and NHS to activate carboxyl group, HPLC condition was suitted, FA-PEG-NH2 and folic acid can be better separated. The retention time of FA and FA-PEG-NH2 were 2.368min and 3.340min respectively, the corresponsive proportion of production was 30.63%±2.34%(n=10). And the yield of the FA-PEG-NH2 was 16.7%±1.43%(n=10), The RT of DSPE and SUC-DSPE were 1.997min and 1.663min respectively, with the proportion of 90.9%±1.03%(n=3). The yield of the SUC-DSPE was 60.9%±2.17%(n=3), The yield of the final production FA-PEG-DSPE was 19%±1.06%(n=4). the final production FA-PEG-DSPE was confirmed by the nuclear magnetic resonance hydrogen spectrum (1H-NMR), The total yield of product was about 2%, which was adequately low.2. Particle diameter of TAX-NLC-FA was 134 nm±18nm(n=3), which was extended significantly compared to non-targeted TAX -NLC(66nm±6 nm).3. Growth inhibition of TAX-NLC-FA on KB cell was increased significantly, observed by MTT, TAX-NLC-FA took action on KB cell after 24h,The 50% inhibiting concentration of TAX-NLC-FA was 1/6 times compared to TAX-NLC.4. Experiment results showed that, The radiolabeling ratio of the labeled compound produced by the modified Ch-T method was about 63.1%±5.7%(n=5) with radiochemical purity about 96.3%±1.3%(n=5). 24 hours later, stored them in NS or alcohol system at 4℃, The radiochemical purity of the product was above 95% and 90% after 120 hours. The labelled product was also stable in serum, after 24h stored at 4℃and 37℃, the radiochemical purities were 92.3%±0.4% and 89.5%±0.6% respectively. The traditional Ch-T method was simple , The radiolabeling ratio of which was 21.4%±3.3%, but it was impossible to obtain the stable radiolabeling product. The radiolabeling ratio of the labeled compound produced by the nitric acid oxidization method was 72.6%±6.0%(n=6), the radiolabeling products of the nitric acid oxidization method was much higher, and the stability of the product of the nitric acid oxidization method was good relatively. At 80℃reaction system, the nitric acid oxidization experiment became difficult to deal and control, also, due to the high temperature, sublimation of the redundant 125I could cause much more radioactive contamination and was unavoidable to breath in, which would be adverse to the health of the research worker and reduce the yield of 125I. Generally, the modified Ch-T method was simple and convenient, the radiolabeling ratio was high and the labeled compound was stable, as so qualified for the isotopic tracing experiment in vivo.ConclusionTo synthesis FA-PEG-DSPE, step-by-step acylation at room temperature, the reaction is not complicated, but the final total yield was not so good, only about 2%. TAX-NLC-FA particle is about 134 nm±18 nm in diameter, and its growth inhibition on KB cell is significant. Measured by MTT, TAX-NLC-FA takes action on KB cell after 24h,and the cytotoxicity of TAX-NLC-FA was 6 times compared to TAX-NLC. Labelling paclitaxel by modified Ch-T and the ratio was high, moreover, the labeled compound was stable. It was qualified for the isotopic tracing experiment in vivo. This method was simple and convenient, and was easy to handle with, the radiolabel ratio of the compound produced by the modified Ch-T method was about 63.1%±5.7%,with purity about 96.3%±1.3%. The stability in serum,normal saline and alcohol of the labeled product after purification was better.It could meet with the requirement of pharmacokinetics tracer experiment. In this study, we have done some basic work for further and better development of the novel targeting nanometer paclitaxel, through analyzing its distribution and pharmacokinetics in vivo.
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