Targeted Pharmacokinetics And Preparation Of Polymeric Micelles Modified With Glycyrrhetinic Acid And Hydrazone Bond

ObjectiveLiver cancer is one of the most common malignant tumors.The chemotherapy drugs play an important role in the process of anti-hepatoma.However,low targeting efficiency and serious adverse reaction are the main drawbacks of them.Liver tumor was proved to have many glycyrrhetinic acid’s specific binding sites and a slightly acidic microenvironment.Therefore,mPEG-HZ-PLA copolymer and GA-PEG-PLA copolymer were synthesized to prepare polymeric micelles modified with glycyrrhetinic acid and hydrazone bond（GA-PEG-HZ-PLA）.The targeting properties of micelles were investigated by targeting pharmacokinetic experiment.Polymeric micelles was expected to produce dual targeting effect of active and pH sensitivity.MethodsThe double amino-terminated PEG（H₂N-PEG-NH₂）was obtained when PEG was azidated and catalytic hydrogenated.GA-PEG-PLA was prepared by a coupling reaction between amino of H₂N-PEG-NH₂ and carboxyl groups of PLA and GA.mPEG-HZ-OH was prepared by a series of reactions of mPEG.mPEG-HZ-PLA was synthesized via ring-opening polymerization of D,L-lactide with mPEG-HZ-OH as the macroinitiator.The structres and molecular weight of two copolymers were confirmed by FTIR,¹H-NMR and GPC.The three kinds of polymeric micelles were prepared by thin film dispersion-ultrasound method with coumarin 6（cou6）as fluorescence probe.Particle size,morphology,encapsulation efficiency and drug loading capacity of polymeric micelles were characterized by dynamic light scattering,transmission electron microscopy and the mini-column centrifuge-fluorescence spectroscopy,respectively.In vitro,the release of the three kinds of polymeric micelles was investigated by dynamic dialysis in different pH media.The micelles were administered intravenously to H22 tumor bearing mice.The contents of Cou6 in blood and tissues were determined through HPLC-FLD with Cou30 as inner standard.The targeting parameters were calculated to evaluate the targeting effect of the polymeric micelles.H22 tumor bearing were established as animal model.The micelles were injected to the H22 tumor-bearing mouse models through caudal vein.Blood,heart,liver and tumor tissue were taken out.The contents of Cou6 in blood and tissues were determined through HPLC-FLD with Cou30 as inner standard.The pharmacokinetics equation was fit and pharmacokinetics parameters were calculated.The targeted action of GA-PEG-HZ-PLA was evaluated by targeted pharmacokinetics.ResultsThe particle size of three kinds of polymeric micelles was about 100 nm and the particle size distribution was more homogeneous.The encapsulation efficiency of polymer micelles was more than 85%,the drug loading capacity was between 4.33⁴.76μg/mg.The release rate of containing hydrazone bond polymeric micelles was faster than that of mPEG-PLA micelles in the pH 5.0medium.In targeted pharmacokinetics experiment,polymeric micelles showed increased MRT,higher AUC and lower CL compared to Cou6 solution in blood.After GA-PEG-HZ-PLA was i.v.administrated,the content of Cou6 in the tumor and liver was significantly higher.And the content of cou6 in tumor was higher than that in liver.The relative intake efficiency,targeted efficiency,relative targeting efficiency and concentration ratio of GA-PEG-HZ-PLA in the tumor were 3.24,4.04,3.00 and 2.47,respectively.ConclusionsTwo copolymers,mPEG-HZ-PLA and GA-PEG-PLA,were successfully synthesized which were applied to prepare a mixed polymeric micelles（GA-PEG-HZ-PLA）.Polymeric micelles could prolong drug circulation in the blood.Meanwhile,GA-PEG-HZ-PLA could be broken and the drug would release in the pH 5.0 medium and more effectively accumulated in liver and tumor compared with mPEG-PLA and mPEG-HZ-PLA.Thus,GA structure and hydrazone bond modified polymeric micelles（GA-PEG-HZ-PLA）have obvious targeting effect,which can provide a new idea for the treatment of liver cancer.