Construction Of A Tumor Microenvironment-Responsive Nano-Drug Delivery System And Its Anti-Tumor Activity

The high incidence and mortality of cancer pose a major threat to human health.Chemotherapy is one of the most commonly used cancer treatments.However,most chemotherapy drugs usually suffer from poor water solubility,lack of selectivity and specificity,which may lead to unsatisfactory treatment effects and serious side effects.Nano-delivery systems(NDS)have unique advantages in improving drug activity and reducing drug toxicity,so they have received extensive attention in biomedical applications.Nanomedicines with specific sizes(20-200 nm)passively target tumor sites through enhanced permeability and retention(EPR)effects,improving drug efficacy while reducing drug toxicity.Tumors have unique microenvironmental characteristics,such as high levels of glutathione(LGlutathione,GSH),low p H,and hypoxia.The stimuli-responsive nano drug delivery system designed according to the tumor microenvironment are enriched in the tumor site through the EPR effect,and the drugs are specifically released under the stimulation of the tumor microenvironment,which increases the uptake of chemotherapeutic drugs by the tumor environment cells,improves the efficacy,and reduces the toxic and side effects.Polyethylene glycol(PEG)is the only polymer material approved by the U.S.Food and Drug Administration(FDA)that can be used in biomedicine.It has good biocompatibility,low toxicity and stability.high advantage.Modification of PEG molecules on the surface of nanocarriers can prolong the circulation time of the carriers in vivo.Doxorubicin(DOX)is an anthracycline antitumor drug widely used in clinical chemotherapy of various malignant tumors.However,free DOX cannot effectively reach the tumor site due to lack of targeting,reducing its bioavailability and causing severe side effects.In this paper,a nano-drug delivery system responsive to tumor microenvironment stimuli was designed and synthesized using polymers with good biocompatibility and degradability as carriers.Mainly complete the following two tasks: 1.Synthesis of p H and GSH dual-responsive nanomicelle delivery system;2.A p H-sensitive,self-assembled nanomicelle delivery system for combined application of chemotherapy and photothermal therapy.The details were as follows.1.The anticancer drug DOX was linked to polyethylene glycol through aconityl bond and disulfide bond to obtain a prodrug PEG-SS-CA-DOX with dual p H and GSH responses.The polymer was an amphiphilic substance,which can self-assemble into nanomicelles in aqueous solution,namely PEG-SS-CADOX nanomicelles.First,the structural and spectral properties of the nanomicelles were characterized.The results showed that the size of PEG-SS-CA-DOX nanomicelles was about 50 nm,the particle size was uniform,and the dispersibility was good.In vitro release experiments showed that the PEG-SS-CA-DOX nanomicelles could rapidly release DOX under the triggering of acidic and reducing environments,exhibiting good p H sensitivity and GSH sensitivity.In vitro cytotoxicity experiments showed that the nanomicelles had a significant inhibitory effect on the growth of 4T1 tumor cells.Cell flow and laser confocal experiments showed that after the nanomicelles reached tumor cells,their acidic environment and high glutathione content would trigger the release of DOX.The results of apoptosis experiments showed that PEG-SS-CA-DOX nanomicelles could obviously induce apoptosis,thereby inhibiting the growth of tumor cells.In addition,in vivo anti-tumor experiments showed that the nanomicelle PEG-SS-CA-DOX had a good therapeutic effect on 4T1 tumor-bearing mice,and at the same time had lower toxic and side effects.2.We developed pH-responsive multifunctional nanomicelles for near-infrared fluorescenceguided synergistic photothermal and chemotherapy.Cy7-PEG-CA-DOX prodrug molecule was successfully prepared using Cy7 as the near-infrared(NIR)fluorophore and photosensitizer,and PEG as the biocompatible carrier,which could self-assemble into Cy7 and DOX in aqueous solution.Nanomicelles with inner core and PEG as outer shell.Characterization by UV-Visible Absorption Spectroscopy(UV-vis),Transmission Electron Microscope(TEM),Infrared Spectroscopy and NMR demonstrated that the nano-loaded drug system Cy7-PEG-CA-DOX was successfully prepared.The particle size of nanomicelles was around 70 nm,with uniform particle size and good dispersibility.In vitro release experiments showed that Cy7-PEG-CADOX nanomicelles were able to release DOX rapidly in an acidic environment,exhibiting good p H sensitivity.In vitro cytotoxicity experiments showed that nanomicelles based on combined chemotherapy-photothermal therapy had a strong inhibitory effect on the growth of 4T1 tumor cells.Flow cytometry and laser confocal experiments have shown that nanomicelles reaching tumor cells trigger the release of DOX and the nearinfrared fluorescent dye Cy7 in their acidic environment.In vivo anti-tumor assay showed that Cy7-PEGCA-DOX nanomicelles showed strong anti-cancer activity against 4T1 tumor-bearing mice.In addition,in vivo fluorescence tracking experiments in animals have shown that Cy7-PEG-CA-DOX nanomicelles had near-infrared imaging and could monitor the in vivo distribution of drugs in real time,which could achieve both diagnosis and treatment of tumors.