Construction Of Highly Loaded And PH-responsive Nanodiamond Drug Delivery System And Its Antitumor Effects

Nanodiamond(ND)has been widely used in tumor treatment through drug and gene delivery due to their advantages,including large specific surface area,good biocompatibility,easy surface modification,etc.However,they still have disadvantages such as low drug loading capacity and relatively little research on drug-resistance.With the development of medicine,it was found that the tumor microenvironment is characterized by microacidity,hypoxia,high concentration of reactive oxygen species(ROS)and high concentration of glutathione(GSH).Therefore,it is important to construct a tumor microenvironment responsive nanomedicine for selective tumor treatment.In this paper,a nanodiamond drug delivery system was designed by tumor micro-acidic environmentresponsive nanomedicine with highly loaded chemotherapeutic drug doxorubicin(DOX)and actively targeting tumor.Then,the anti-tumor effects of nanomedicine were carried out,the main research contents are as follows.1.Based on the acidity difference between tumor microenvironment and normal tissue,a polyaspartic acid-modified ND as carriers was designed,combined folic acid(FA)with active targeting function and acid-sensitive hydrazone bond-coupled DOX to obtain an integrated drug delivery system(ND-PA-HYD-FA/-DOX,NPHF/D)for oncology treatment with drug loading capacity of 201±3 μg/mg.ND drug delivery system(ND-PAHYD-DOX,NPHD)without FA was used as a control.The nanodrugs NPHF/D were characterized by IR,Raman and fluorescence microscope,etc.It was found that the fluorescence of covalently coupled DOX was quenched in NPHF/D.In vitro drug release was performed in a micro-acidic environment(pH 4.5-6.5)and a normal physiological environment(pH 7.4),and it was found that the drug release rate was 85% at pH 5.0 and less than 10% at pH 7.4,indicating that NPHF/D has pH-responsive drug release properties.2.Taking advantage of acidity difference between tumor cells and normal cells,it was observed that the fluorescence of the quenched nanodrug system NPHF/D was recovered in human breast cancer cells(MCF-7)and was mainly located in the lysosome,while the fluorescence remained in the quenched state in human normal hepatocytes(HL-7702)via laser confocal microscopy,demonstrating the selective tumor recognition for nanodrugs.Laser confocal microscopy and flow cytometry were used to demonstrate the active tumor targeting effect of the nanodrug NPHF/D.By CCK-8 assays and real-time cellular analysis,the NPHF/D drug system can kill MCF-7 cells and He La cells,and the inhibition effect of the NPHF/D on tumor cells far exceeded that of the NPHD,while it was basically non-toxic to HL-7702 cells.The above results fully demonstrate that NPHF/D drugs have activable fluorescence and toxicity in tumor cells,while they remain "inactivated" in normal cells.The reversal of drug resistance was investigated using MCF-7/ADR as a model,the results displayed that the inhibition rate was up to 85% of NPHF/D against MCF-7/ADR at a DOX concentration of 50 μg/m L,while the free DOX with the same concentration only inhibited30%,indicating that the nanomedicine NPHF/D has reversal of drug resistance.In addition,the nanodrugs was injected into tumor-bearing mice by intraperitoneal injection,and the fluorescence imaging was detected in mice and the major organs with a in vivo imager.These resulted revealed that the NPHF/D drugs have the highest mean fluorescence intensity at the tumor site,indicating its active tumor targeting properties.