Application And Research Of GGT-responsive Charge-reversal Drug Carrier

In the process of cancer treatment,the advent of nano drug delivery system not only avoids the toxic and side effects of chemotherapy on people's body,but also avoids the body damage caused by tumor cutting,which brings great hope for the cancer treatment in the future.However,due to the high density of tumor tissue,it is difficult for nanodrugs to enter tumor tissue or tumor cells to complete drug delivery process.The inefficient penetration of drugs through tumor has become a bottleneck to restrict the development of nanodrugs.Here,we designed and prepared a drug delivery system with charge reversal based on the fact that high concentration of ?-glutamyl transpeptidase(GGT)in tumor microenvironment can specifically recognize and catalyze the substrate containing gamma glutamyl group,thus exposing the amino groups in the substrate.The physicochemical characteristics of the system were systematically studied,and its biological toxicity and anti-tumor effect in vivo and in vitro were systematically evaluated.(1)Through the simple dehydration condensation reaction between Boc protected glutamine and L-2-aminobutyric acid,the responsive molecule *GGT was prepared.After simple modification,the responsive molecule DGGT was prepared containing two *GGT.GGT-PEG-PCL and DGGT-PEG-PCL were prepared by the reaction of GGT and DGGT with amino terminated and maleimide terminated amphiphilic block copolymers,respectively.Based on the self-assembly of block copolymers to form micelles,GGT responsive drug delivery systems GGT-PEG-PCL@CPT and DGGT-PEG-PCL@CPT with hydration particle sizes of 89.6 nm and 94.3 nm and TEM particle sizes of 40nm-60 nm were prepared.The system can not only maintain electronegativity when blood circulates for a long time,but also present positive electricity when it reaches the tumor site.It can also transport nano drugs to the depth of tumor by using transcellular transport.(2)MTT assay showed that when the concentration of the carrier reached 120 ?g/m L,the killing power of the carrier to the GGT positive cell line HepG2 cells was still small,and the cell survival rate was still above 85%,indicating that the carrier had good biocompatibility.After drug loading,when the drug concentration was 10 ?g/m L,the killing effect on HepG2 cells was greater.In addition,we also demonstrated the endocytosis of HepG2 cells and GGT negative cell line NIH-3T3 cells by laser confocal microscopy,the results of flow cytometry further confirmed the endocytosis.In the following mouse tumor inhibition experiment,it also showed good tumor inhibition effect,good biocompatibility,and no obvious biological toxicity.(3)In addition,we further introduced the cell penetrating peptide(TAT),which linked three *GGT,and reacted with Mal-PEG-PCL to prepare GGT-TAT-PEG-PCL.We systematically studied the structure and morphology of the vector,The results of MTT test and endocytosis test in HepG2 cells and NIH-3T3 cells showed good results.In a word,GGT responsive charge reversal drug delivery system can well deliver drugs to tumor sites,a large number of nanodrugs are swallowed by cells,showing a good therapeutic effect,greatly reducing the damage to the organism.It has certain guiding significance for active drug transport,endocytosis and tumor infiltration.