Preparation Of Stimuli-responsive Pillararene Nanocarriers And Their Application In Anti-intracellular Bacteria

When bacteria such as MRSA and Salmonella invade the body,the immune system can quickly activate the response mechanism to remove most bacteria,but some can survive inside immune cells such as macrophages to form intracellular bacteria.Intracellular bacteria can easily lead to chronic infectious diseases and recurrent infectious diseases.However,it is difficult to treat intracellular bacterial infections because many antibiotics don't have the abilities to get into infected cells or accumulate enough intracellular concentrations.Therefore,it is often necessary to use high-dose antibiotics for a long time to treat the infection caused by intracellular bacteria,which will produce adverse effect,but also lead to the emergence and spread of bacterial resistance.Although the drug delivery system(DDS)can improve the intracellular concentration of antibiotics,but the traditional drug delivery system lacks the targeting abilities,producing off-target effects and side effects.Strategies that target the macrophage and deliver the antibiotic into macrophages can improve the performance of antibiotics in treating intracellular bacterial infections.Therefore,we have developed targeted antibiotic delivery systems that could deliver antibiotics into the infected macrophages and release the antibiotics in the intracellular microenvironment,significantly increasing the intracellular concentration of antibiotics and enhancing their antibacterial activities in treating intracellular bacterial infections.This thesis consists of three parts:(1)Preparation of GSH responsive pillararene nanoparticles and their application in treating intracellular MRSA infection;(2)Preparation of enzyme responsive pillararene-based vesicles and their application in treating interacellular salmonella infection;(3)Preparation of enzyme/p H dual responsive pillararene vesicles and their application in treating intracellular MRSA infection.(1)Preparation of GSH responsive pillararene nanoparticles and their application in treating intracellular MRSA infection.A novel targeting drug delivery system(WP5?G)based on the host-guest interaction between a mannose-modified pillar[5]arene(WP5)and guest molecule G containing near-infrared fluorescent groups had been successfully developed.WP5?G could be activated to restore the NIR fluorescence by glutathione(GSH)which be used to track and locate the intracellular location and aggregation of WP5?G nanoparticales.The WP5?G nanoparticles could load the linezolid(LZD)to form the loading drug nanoparticles(LZD-WP5?G)with good encapsulation rate.In addition,the LZD-WP5?G could target the macrophages and deliver the LZD into macrophages via the mannose receptor mediated endocytosis.Meanwhile,the LZD-WP5?G could be stimulated to release the LZD by cellular GSH,significantly enhancing the anti-intracellular activity of LZD.Besides,the LZD-WP5?G nanoparticles exhibited excellent biocompatibility.(2)Preparation of enzymes responsive pillararene-based vesicles and their application in treating interacellular salmonella infection.Novel mannosylated pillar[5]arene was synthesied and could self-assembled into supramolecular vesicles(MP5-Gen)loaded with gentamincin(Gen)which target into macrophages via mannose receptor.Extracellular release experiments indicated that MP5-Gen vesicles rapidly released gentamicin under the stimulation of cathepsin B.In RAW 264.7 cell model of salmonella infection,MP5-Gen vesicles improved the intracellular concentration of gentamicin,significantly enhancing the activities of gentamicin against intracellular salmonella with low cytotoxicity.(3)Preparation of enzyme/p H dual responsive pillararene vesicles and their application in treating intracellular MRSA infection.A novel mannosylated pillar[5]arene vesicles(Man@AP5)has been developed which could efficiently encapsulate vancomycin(Van)and target into macrophages via mannose receptor mediated phagocytosis.Extracellular release experiments indicated that Man@AP5-Van vesicles could be triggered for rapid Van release by lysosomal acid and cathpsin B.Intracellular fluorescence imaging indicated that the mannose receptors on the macrophage surface could facilitates phagocytosis of the Man@AP5vesicles.Meanwhile,the anti-intracellular MRSA experiments showed that the anti-intracellular MRSA activity of Man@AP5-Van vesicles was about 29 times higher than that of free vancomycin.Besides,cytotoxicity experiments indicate that Man@AP5-van vesicles had low cytotoxicity and good biocompatibility.