A Traceable Drug Carrier With Long Circulation,Targeting,Controlled Release And Escape Function

Nano drug delivery systems have many advantages as relatively mild cancer chemotherapy.However,in clinical practice,it has many shortcomings,such as easy phagocytosis by macrophages,short cycle time,release drug without discrimination,low nuclear uptake rate,etc.,which reduces the efficacy of liposomes,resulting in unsatisfactory therapeutic effects and limitations the application.Therefore,this thesis aims to develop a drug carrier with improved drug efficacy and low toxicity by combining magnetic resonance imaging,active folic acid targeting,pH-light dual-touch release,polyethylene glycol long-circulation and melt-film endosomal escape function to achieve precision medicine.Firstly,a Gd-DTPA-ONB molecule with both nuclear magnetic resonance tracking ability and pH-light dual controlled release ability was designed and synthesized.At the molecular level,the photolysis and pH dissociation properties of the compound were presumed.During the dissociation process of GDO liposomes(prepared by pure Gd-DTPA-ONB lipid),the particle size of the liposomes increased with the extension of illumination time.By studying the photolysis behavior of drug-loaded liposomes,it is speculated that there are two kinds of competitive reactions in the release process,which is the dissociation-remodeling and drug precipitation process;When the pH deviates from the neutral condition,the longer the illumination time,the higher of the release efficiency;The relaxation time of Gd-DTPA-ONB lipid is 4.11 times higher than that of clinical application of Gd-DTPA.Both in vitro and in vivo nuclear magnetic imaging and in vivo fluorescence imaging have proved that GDO liposome has superior imaging effect;the cytotoxicity,intracellular imaging and tumor treatment inhibition efficiency all demonstrated the potential of pH-light-controlled release of GDO liposomes in tumor therapy.Secondly,the Fa-ONB molecule with active targeting and pH-light release function was synthesized.The photolysis and pH dissociation ability of Fa-ONB at the molecular level were examined by infrared,ultraviolet,mass spectrometry and thin-layer chromatography.FOBD73,FOBD55 and FOBD37 liposomes with well stability and high dissociation effect were screened by drug encapsulation,osmotic release effect,and particle size change during pH-photodissociation process;Cytotoxicity,flow cytometry and confocal imaging were used to verify the active targeting performance and photocatalytic behavior of FOBD liposomes.Using in vivo fluorescence imaging and tumor treatment efficiency to evaluate the application potential of FOBD55 liposome,it was found that the average tumor size of the experimental group was 7.59 times smaller than that of the PBS control group,so the application of FOBD liposomes is beneficial to improve the targeting efficiency of drugs in tumors and help regulate the release of drugs in the lesions.Again,inspired by the action mechanism of the membrane protein,six kinds of polyethylene glycol lipids with different chain lengths and different end groups were designed and synthesized.The layered hydrogel structure was used to simulate the contact behavior between liposomes and endosomes during intracellular uptake.In different water content,X-ray small-angle scattering was used to determine the variation of the layer spacing between samples with different structures and different chain lengths.It is found that DEA-type lipids with double hydrophobic ends can form a reversible "bridge" structure between adjacent layers,and the limited layer spacing could facilitate membrane fusion.Among all DEA lipids,the ADEA structure with asymmetric hydrophobic ends is more effective than the SDEA structure with symmetric hydrophobic ends.The size of liposomes,TEM morphology,intracellular uptake,and confocal imaging demonstrated that when the lipid content of ADEA2K was 2.5 mol%,it had the best endosomal escape effect,and the extend effect of cycle time was verified by in vivo small animal fluorescence imaging.Finally,a multifunctional drug carrier was prepared by prolonging the Gd-DTPA-ONB,Fa-ONB,ADEA2K and DOPC lipids.By cytotoxicity,cell uptake,confocal imaging,small animal fluorescence and nuclear magnetic imaging,it is verified that the compound liposome can exist in the body for more than 24 hours,effectively circumvent the immune system,monitor the drug transport path through nuclear magnetic resonance,actively target the lesion and reduce the damage of the drug to normal tissues by regulating the timely release of the drug,and can increase the uptake of the drug by the diseased cells by means of the escape process of the endosomes.In the nude mice treatment experiment,the tumor size in the light group was 9.92 times smaller than that in the PBS control group,and the therapeutic effect of the multifunctional GFDA liposome was obvious,indicating that the GFDA liposome has potential application in precise,high-efficiency and low-toxic medical treatment.