Studies On Preparations And Controlled Release Of Stimuli Responsive Nano-micelle Based On Poly(L-glutamic Acid)

Polymer micelle was an ideal drug release system, its special core-shell structure can be used as anticancer drugs of micro-memory. However, the clinical trials have found that the traditional polymer micelle, which is lack of special recognition and binding function, cannot make response to tumor cell. The anticancer drug can not accurately and timely arrive at the lesions and have low treatment effect. In order to solve this problem, some targeted and sensitive groups can be introduced in polymer micelle, which can make fast response and targeting drug delivery for lesion site. The perfect design concept will undoubtedly make the release of the drug to achieve positioning, timing, and duantitative effect, which can improve the biological utilization of drugs. Therefore, the current work aims at designing and preparation of stimuli responsive polymer micelle for active loading and triggered intracellular release of doxorubicin and expects to get application in the diagnosis and treatment of tumors.we have successful synthesized amphiphilic poly(N-isopropylacrylamide-co-poly ethylene glycol)-poly(L-glutamic acid-γ-benzyl ester). Then the temperature and p H dual responsive polymeric nano-micelle was synthesized from the γ-benzyl ester group turning to be γ-hydrazide group by hydrazine hydrate, Doxorubicin(DOX) was covalently loaded on the terpolymer. The structure of polymer was confirmed by IR, 1H-NMR and GPC. The morphology of micelle, LCST and its drug release behaviors were characterized by UV, SEM and nanoparticle size analyzer. It was observed that the LCST of PNN-DOX micelle was 38 ℃. The polymer was formulated into spherical micelle with uniform distribution. The vitro release extensively indicated excellent temperature and p H responsive. By choosing 3T3 and He La as cell model, the cell experiment and MTT assays revealed that the PNN polymer possessed perfect biocompatibility and the PNN-DOX micelle showed obvious inhibition effect for the growth of He La cellsIn order to enhance the stability of micellar nanoparticles, we have prepared amphiphilic poly(ethylene glycol)-poly(L-glutamic acid-γ-benzyl ester) and cross-linked derivative from cysteamine as cross linking agent via chemical reaction with γ-benzyl ester group. Then the p H and reductive dual responsive PLS-DOX was synthesized from HBr/HOAc, and doxorubicin(DOX) was loaded on terpolymer by electrostatic interaction. The above methods were used to characterize the structure and properties of polymer and its micelles. The result showed that both the uncrosslinked and crosslinked polymeric micelle were successfully prepared with the spherical shape.Compared with PLE uncrosslinked micelle, the PLS micelle after crosslinked demonstrated markedly enhanced stability against extensive dilution and high salt concentration. In the simulation of intracellular redox conditions(10 m M GSH), the size of PLS crosslinked micelle have increased for the rapidly response and fracture of disulfide bond. The in vitro release indicated that the PLS-DOX micelle possessed obvious p H and reducing responsive. The cell experiment and MTT assays demonstrated that the PLS crosslinked micelle was practically nontoxic, and the PLS-DOX micelle can make fast response and targeted drug delivery after entering tumor cells, which revealed strong inhibition and killing effect on He La cells. The stimuli responsive polymer micelles based on the current work have great potential in liver tumor- targeted chemotherapy.