Study On Properties Of Targeting Drug Delivery System Carrier Based On PLA

The targeted therapies have been obtained more and more attention as the tumor incidence increases recently. Among of which, folate-mediated targeting-drug released system (FMTDRS) based on biodegradable and biocompatible polymers have been a hot point research throughout the world. Comparing with the conventional tumor therapies, FMTDRS have obviously targeting effect on tumor cells and have slightly inhibited effect to normal tissue cells, which provide a guarantee for targeting therapies. But to our knowledge, there is little research only pure without drug-loaded nanoparticles materials. Hereon, folate conjugated poly(ethylene glycol) block poly(D,L-lactic acid)(FA-PEG-PLA) was synthesized from poly(D,L-lactic acid)(PLA) with different molecular weight, amino-terminated poly(ethylene glycol)(NH2-PEG-NH2) and folic acid (FA), using dicyclo-hexylcarbodiimide (DCC) and N-hydroxy-succinimide (NHS) or4-dimethylaminopyrid (DMAP) as dehydrating agent and activating agent respectively. Fourier transform infrared spectrometry (FTIR), nuclear magnetic resonance spectrometry (NMR), differential scanning calorimeter (DSC) and contact angle meter were employed to characterize the structures and properties of the obtained polymers. Nanoparticles (NPs) were further fabricated from FA-PEG-PLA by using solvent evaporation-induced interfacial self-assembly method, and thereafter, the hemolysis, biodegradation, cell proliferation and cytotoxicity, and selecting capability to different cells in vitro were investigated to nanoparticles. The main works and conclusions are summarized as follows:(1) FA-PEG-PLA was prepared of FA, NH2-PEG-NH2and PLA via active ester method using DCC and NHS or DMAP as dehydrating agent and activating agent respectively. Then, an extensive investigation effort was expended in understanding the effects of reaction time on grafting folate onto FA-PEG-PLA.①FTIR,1H NMR analysis showed that FA-PEG-PLA was successfully synthesized by using above mentioned method. And as the reacting time, more and more FA grafted on copolymer. During the first24h of reacting time, the ratio of graftion increased more quickly but after that it became slowdown, which agreeing with the reaction balance law that reaction rate slowed down gradually along with the formation of product and the reduction of reactant;②1H NMR analysis indicated that the percent grafting of FA onto FA-PEG-PLA was in the range of11.6%-15.7%(mol%) or0.39%-0.53%(wt%);③DSC analysis showed that multicomponent polymer appeared the microphase-separation along with the increase of molecular weight of PLA in certain case, glass transition temperature (Tg) changing from one to two, and the difference temperature range appeared to two raw materials temperature intermediate closing tendency, all which also showed that the obtained materials was component polymer;The combination of the test results of②and③analysis showed that the obtained polymer was multicomponent polymer;④The static water contact angle test results showed that the introduction of FA had little effect on material hydrophobicity, and which is mainly decided by composting of PEG and PLA chain length;The combination of the test results of③and④analysis indicated that:The introduction effect of FA on coupling material hydrophilic and hydrophobic property would-be ignored in most time but on the material microphase-separation sometimes maybe play a key role;⑤The result of the degradation of nanoparticles showed that the nanoparticles degradation speed was very fast, mainly for the bond fracture in disorder in the first three weeks, and the residues molecular weight was25%of its initial value after three weeks. As the degradation, the ratio of bond fracture became slowdown and the residues molecular weight gradually decreased, reaching8.8%of its initial value after seven weeks. According to the fitting equation of a degradation curve, the nanoparticles will be degraded completely in eighth weeks.(2) The obtained FA-PEG-PLA was further used to fabricate nanoparticles by solvent evaporation-induced interfacial self-assembly method and the nanoparticles surface morphology, size, distribution, zeta potential, critical micelle concentration (CMC) and the dilution stability were characterized respectively.①The particles prepared was spherical and size was in a range from65to160nm characterized by FESEM and DLS, and at the same time, nanoparticles surface carrying the negative charge;②The dilution stability test result indicated that the CMC of nanoparticles could meet the requirements for clinical application and the nanoparticles could keep stable micelle structure in vivo as local injection of drug release system carrier, hoping to prevent drug "bursting" or "lagging" release;③By the study on preparing technology of nanoparticles, we found the maximal stable concentration of the obtained FA-PEG-PLA nanoparticles was0.9mg/mL, and on this condition, the obtained nanoparticles size was below200nm;④The hemolysis results showed that these nanoparticles have good biocompatibility, and which has not dose-dependent when the particle size was bigger than121nm.(3) The effect of polymer extraction solution on different cells was studied by cell counting kit-8(CCK-8), and then, an extensive investigation effort was made to determine the right particles size using for targeting tumor drug release system carrier, which was about the effect of different size/dose nanoparticles on EC and MCF-7cell proliferation and cytotoxicity in vitro.①The cell proliferation and cytotoxicity of FA-PEG-PLA NPs extraction solution were evaluated by means of CCK-8assay using MCF-7and EC as model cells. The result showed that MCF-7whose cytotoxicity grade kept1was more sensitive than EC to extract, and that of EC changed from0to1to0according to the relationship between cell proliferation rate and cytotoxicity grade of USP, suggesting that extract is almost non-toxic to normal tissue cells;②The effect of different size nanoparticles on MCF-7and EC cell proliferation were investigated according on①of (3) method to determine the right particles size for targeting drug release system. The result told that the difference was happened between two kinds of cells. And by this way, it was found that the particles size about121nm was the right size for targeting tumor drug release system, which affected MCF-7proliferation and not for EC, furthermore, it’s a guarantee for nanoparticles promising higher drug encapsulation;③In this study, MCF-7cell proliferation showed dose-dependence of nanoparticles but EC not.