Preparation Of Stimulus-responsive Nano-drug Delivery System And Application Research In The Field Of Combination Therapy

In recent years,the emergence of drug delivery systems has solved the drawbacks of tumor drugs in clinical practice,such as short circulation time and greater toxic side effects on various organs.However,due to the easy metastasis and drug resistance of tumor cells,the delivery system carrying a single drug often fails to achieve the desired therapeutic effect.At present,the application of nano-delivery systems to combination therapy has been proposed,and the drawbacks of single drug delivery systems can be solved by combining different treatment modalities.In this paper,based on the tumor-specific environment,a pH/glutathione（GSH）responsive multifunctional nanodrug delivery system was prepared.The main research contents of this paper are as follows:1.SynthesisofaGSH-sensitivefunctionalizedpolymer P（MA-SS-TMOBA）-PEG-DTPA-VI-PBA,which can self-assemble in water to form core-shell-shaped nanomicelles and coat the antitumor drug doxorubicin（DOX）and photosensitizer Rose Bengal（RB）to the hydrophobic core.At the same time,the imidazole in the polymer was coordinated with the Zn O quantum dots（QDs）to prepare the Zn O-micelle composite nanocarrier.Depending on the coordination effect of Zn O QDs,the carrying capacity of DOX was increased and glucose oxidase and catalase were carried,achieving a combination of starvation therapy,photodynamic therapy and chemotherapy.It is worth noting that glucose oxidase not only consumes glucose at the tumor site,it also provides a high concentration of H₂O₂for catalase to produce O₂.The continuous improvement of O₂concentration at the tumor site can accelerate the oxidation of glucose in cells,enhance the PDT efficacy of the photosensitizer RB,and reduce the high drug resistance of tumor cells to DOX.In the experiment,we analyzed the structure of the monomer and polymer by ¹H NMR,and observed the size and morphology of the polymer micelles by dynamic light scattering（DLS）and transmission electron microscopy（TEM）.The results showed that the drug delivery system presented a spherical distribution of 129 nm diameter in water.In order to enable the drug delivery system to reach the tumor site accurately,we used phenylboronic acid（PBA）as the targeting agent and SPECT imaging to verify the targeting effect.The results showed that the nano-delivery system had a good cumulative effect in tumor sites.This further enhanced the effectiveness of the combination therapy.2.Synthesis of a pH-sensitive drug delivery system Dex-Cys-RB-PBA-CBA-DOX,which loads Cd Te QDs by the coordination of cysteine sulfhydryl group??to electrostatically adsorb NO donor（L-arginine）.The nano drug delivery system enables a combination of chemotherapy,PDT and NO gas therapy.Its structure and properties were characterized by ¹HNMR,UV-Vis,DLS and TEM.PDT and gas therapy were tested in vitro by uric acid and rhodamine B spironolactone.The results indicated that the RB carried by the drug delivery system could produce reactive oxygen species（ROS）under the light conditions,and L-arginine could also produce NO gas under the oxidation of H₂O₂.In in vitro cell experiments,compared with free doxorubicin（DOX）,this combination therapy has a lower half inhibitory concentration(IC₅₀)on B16F10cells,indicating that the drug system has an ideal efficacy in combination therapy.3.Synthesis of a GSH-responsive dextran-mercaptopurine prodrug（Dex-PTA-DTPA-PBA）to coordinate Zn O QDs for multiple drug delivery（DOX,5-fluorouracil,6-mercaptopurine）,drug release can also be triggered by pH and GSH.In order to enhance the anti-tumor effect,photodynamic therapy（PDT）was performed using an inorganic photosensitizer Cd Se QDs.Under light conditions,Cd Se QDs can produce cytotoxic ROS（·OH）.It is worth noting that we found that the release of6-mercaptopurine could consume GSH at the tumor site.It can effectively amplify oxidative stress in cells through the production of·OH produced by Cd Se QDs,which is more conducive to cancer cell apoptosis.Compared to free DOX,the drug system can reduce the IC₅₀（half cell inhibitory concentration）of B16F10 cells to 0.40μg/m L under light conditions.It indicates that the nano drug system with sialic acid as a target substance has achieved an ideal anti-tumor effect and has broad application prospects.