| Cancer has become the most dangerous diseases for people’s health. Themain treatments for cancer include radiotherapy and chemotherapy besidessurgery. Due to the lack of specific and selective of antitumor drugs to tumorcells, there are the same destroy effects on normal body cells. Therefore, it ismore and more important to treat tumor by using tumor targeting therapy.Antitumor targeting drug delivery system is an important aspect of tumortargeting therapy. The effective anticancer drugs are selectively delivered tothe tumor, and the reasonable dose of drug is controlled, so as to reduce theside effect of antitumor drugs on normal tissues. Magnetic targeting drugdelivery system is one of kind of targeting drug delivery system, which iscomposed of drug, magnetic particles, and matrix material. The system canselectively deliver drugs and locate them in tumor region under externalmagnetic field. It is very useful for the treatment of cancer. Therefore, the aimof this research is to design a new magnetic targeting drug delivery system.Objective: To design and prepare a magnetic polymer drug-loadedmicelle which has magnetic response under magnetic field.Firstly, five kinds of block copolymer with different molecular weight aresynthesized. Based on the characterization of the block copolymers, theappropriate polymer is determined. Secondly, the monodispersesuperparamagnetic Fe3O4nanoparticals are prepared by solvothermal method.Finally, with selecting MePEG-PCL as polymer, hydrophobic Fe3O4nanoparticles as magnetic material, and doxorubicin as a model drug, drugloaded polymer micelle and drug loaded magnetic polymer micelle are bothprepared by studying the preparation conditions. The contents of drug in thetwo polymer micelle systems are assayed, and properties of the micellesystems are also detected. The curves of drug release of doxorubicin are measured under different pH conditions. Furthermore, cytotocity of differentmicelle systems are investigated, and magnetic targeting research ofmagnetic micelles are conducted in vitro. It is hopeful to find a new methodto prepare magnetic targeting drug delivery system.Methods: Block copolymer with different molecular weight and thelength of chains were synthesized by ring opening polymerization. WithMePEG or PEG, and ε-CL as reactants, stannous octoate as catalyzer, fivekinds of block copolymers with various ratios of PEG/PCL were synthesized(two MePEG–PCL di-block copolymers and three PCL–PEG–PCL tri-blockcopolymers). The number-average molecular weight (Mn), weight-averagemolecular weight (Mw) and molecular weight distribution of these blockcopolymers were measured by gel permeation chromatography (GPC). Thecomposition of the copolymers was determined by1HNMR spectra andFourier-transform infrared spectroscopy (FT-IR).In order to investigate the ability of polymer to form micelle, the criticalmicelle concentration of polymers were determined by fluorescence method.Doxorubicin loaded polymer micelle were prepared by dialysis method. Theeffects of condition on the size of polymer and drug loaded content werediscussed. The micelle morphology was determined using transmissionelectron microscope, and the sizes of micelles were measured by Particle sizeanalyzer. The release experiment of Doxorubicin loaded polymer micelle invitro was carried out in different pH values aquatic medium.Monodisperse Fe3O4NPs were prepared by solvothermal processes. Thesolvothermal reaction of Fe (acac)3decomposition was carried out at a mildtemperature in the presence of oleylamine and n-hexane. The effects of thesynthesis conditions, including the solvents/ligands, temperature, and reactiontime, on the physiochemical properties of Fe3O4NPs were investigated. Thesamples were characterized by powder X-ray powder diffraction (XRD),Fourier-transform infrared (FT-IR) spectrometer, transmission electronmicroscope (TEM). Magnetization was determined using a vibrating samplemagnetometer (VSM). Thermogravimetric (TG) analysis of the powder samples was carried out using thermogravimetric analyzer.Taking Superparamagnetism Fe3O4as magnetic material, doxorubicinloaded magnetic micelle was prepared by dialysis method. The micellemorphology were observed using TEM, and the sizes of micelles weremeasured by Particle size analyzer. Magnetization of the magnetic polymermicelle was determined by VSM, and the Magnetic response experiment wascarried out under external magnetic field in vitro. The release experiment ofdoxorubicin in vitro which carried out under different pH conditions revealedthe release characteristics of doxorubicin loaded magnetic polymer micelle.The in vitro cytotoxicity of the drug in different micelle systems wasdetermined by CCK-8assays using K562cell. The magnetic target ofmagnetic polymer micelle in vivo was preliminary studied using mice.Results: Block copolymers were synthesized by ring-openingpolymerization. The reaction temperature is130℃, and reaction time is36h.The amount of Stannous octoate, as catalyzer, is1/200of the weight of ε-CL.1HNMR spectra show that there are chemical shift of PCL and MePEG chains.FT-IR spectroscopy of polymer appeared2946cm-1and2893cm-1band whichare sign to–CH stretching vibration,1734cm-1for C=O, and1195cm-1for C-O.This means that there are both structure units of PEG and PCL in polymermolecular. Only a single peak appears in GPC spectra, which means that thereis one species polymer molecular in system. The index of disperse of twokinds polymer is1.23and1.27, respectively, which indicate that polymer ismonndisperse. Molecular weights of polymers from the results of1HNMR andGPC are coincided with those from prediction.Monodisperse Fe3O4NPs were prepared by solvothermal reaction. Thesolvothermal reaction of Fe(acac)3decomposition was carried out at190℃for8h in the presence of oleylamine and n-hexane. The particle sizes of the Fe3O4NPs can be controlled by varying the volume ratio of n-hexane to oleylamine.FT-IR spectra and TG measurement reveal that oleylamine molecules adsorbon the surface of Fe3O4particles. Oleylamine was used as a reducing agent andstabilizer. The oleylamine-coated NPs possess changeable surface properties, improved lipophilic property, and increased combination ability with polymers.Hydrophobic Fe3O4NPs scattered in oil phases such as n-hexane, and yield ablack homogeneous dispersion which stable for weeks at room temperature.Doxorubicin loaded polymer micelles were prepared by dialysis method.The sizes of micelles from tri-block polymer are larger than those fromdi-block polymer. The drug loaded content is mainly related with the length ofhydrophobic chain of copolymer. With the same molecular weight, thedrug-loaded content of di-block copolymer micelles is greater than that oftri-block copolymer micelles. TEM pictures show that polymer micelles arecore-shell types with uniform sharp and size. The size of black micelle is65.2nm, and doxorubicin loaded micelle nearly reaches76.6nm. Zeta potentialof drug loaded micelle is-5.79mv. The drug loaded content of doxorubicinloaded micelle is (1.8±0.2)%, and the entrap efficiency is (45.2±2.1)%measured by RP-HPLC. The release experiment of doxorubicin in vitroshowed that the release speed of doxorubicin entrapped in micelle is slowerthan that of free doxorubicin, and the speed is dependent on pH value ofmedium.Doxorubicin-loaded Magnetic polymer micelle was prepared using7nmFe3O4as magnetic material. The magnetic polymer micelle is core-shellstructure spherical particle. The Fe3O4loaded content is15.2±2.3%(w/w)measured by UV-Spectrophotometry, and doxorubicin loaded content is1.8±0.2%(w/w) measured by RP-HPLC. The size of doxorubicin loadedmagnetic polymer micelle was larger than that of blank micelle. The magneticmicelle showed powerful magnetic response under external magnetic field. theSaturation magnetization of Fe3O4which entrapped in polymer micelledecreases from59.70emu/g to24.71emu/g. The release curves ofdoxorubicin loaded in magnetic micelle were similar to that of doxorubicinloaded in polymer micelle. The release pattern is two segments mode, and therelease speed is dependent on the pH values of medium. The experimentalresults show that it is successful to prepare the magnetic polymer micelle.The cytotoxicity experiment showed that doxorubicin has different inhibition for the proliferation of K562cells in different carrier environments.The free-doxorubicin has the highest inhibitory effect in24h, and theinhibitory effect of doxorubicin which loaded in micelles increasessignificantly in48h, while the inhibitory effect of free doxorubicin increasesslowly. The results show that the release of doxorubicin which loaded in themicelle has sustained release effect.The fluorescence intensities of doxorubicin in cells were measured byflow cytometry. The fluorescence intensity of doxorubicin in magnetic micelleis higher than those of the other systems. It seems that Fe3O4NPs can increasethe concentration of doxorubicin in cells.The magnetic targeting experiments in vivo showed that theconcentrations of doxorubicin in mice kidneys fastened with external magneticfield are higher than those of in kidneys without external magnetic field. TheHE staining experiments of mice kidney tissue observed that the number ofFe3O4obviously increased in the kidneys that were fastened with externalmagnetic field. The results indicate that drug loaded magnetic polymer micelleis a drug targeting drug delivery system.Conclusions: Five kinds of black copolymer PEG-PCL are synthesizedby ring opening polymerization. The results of1HNMR, GPC, and DSCindicate that the properties of polymer are consistent with expected design.Hydrophobic Fe3O4nanoparticls are prepared by solvothermal reaction in mildtemperature. The particle sizes of the Fe3O4NPs can be controlled by varyingthe volume ratio of n-hexane to oleylamine. Doxorubicin loaded polymermicelles are prepared using PEG-PCL block polymer. Polymer micelles arecore-shell types with uniform sharp and size. Magnetic doxorubicin loadedpolymer micelles are also prepared using Fe3O4NPs as magnetic material. Therelease pattern of doxorubicin from micelles is two segments mode, and therelease speed is dependent on the pH values of medium. Doxorubicin hasdifferent inhibition for the proliferation of K562cells in different systems. Therelease of doxorubicin which loaded in the micelle has sustained release effect.Magnetic doxorubicin loaded polymer micelles display magnetic responds in vivo under external magnetic field. Magnetic drug loaded polymer micelle is akind of drug targeting drug delivery system. |
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