Liposome-encapsulated Nanoparticles Promote Antibacterial Efficacy In Response To Biofilm Microenvironment

Bacterial infections account for high human morbidity and mortality,and bacteria are prone to formation of biofilms to provide a protective barrier against attacks from immune cells and antibiotics.Currently,the biofilm treatment involves destruction of the biofilm matrix to increase the antibiotic sensitivity.However,the dispersal of biofilms usually leads to bacterial escape into surrounding tissues to induce tissue inflammation,blood infection,even sepsis.In addition,to address the antibiotic resistance in biofilms,many non-antibiotic agents have been investigated,but these treatments have curtain in vivo toxicity.Therefore,it is essential to modulate the biofilm microenvironment to enhance the sensitivity of bacteria to antibiotics and destroy efficiently bacteria without significant breakage of the biofilm matrix.In this thesis,PAm Pt was obtained by in situ deposition of platinum（Pt）on polydopamine（PDA）nanoparticles（NPs）with loaded ampicillin（Amp）,and then coated with luteolin（Lut）-loaded vitamin E polyethylene glycol succinate（TPGS）liposomes through membrane extrusion to prepare PAm Pt@Lut-Lip/Tp NPs.For comparison,rhamnolipid（RHL）was mixed into liposomes to prepare PAm Pt@Lut-Lip/Rl,and RHL could degrade glycolipids in biofilms to disperse them.Hydrophilic polyethylene glycol chains in TPGS increase the permeability of NPs in biofilms through hydrophilic-hydrophobic interactions,and liposomes could release Lut in response to lipase in biofilms to block quorum sensing signals between bacteria.Pt could catalyze the production of O₂ from H₂O₂ in the biofilm to change the anoxic environment in biofilms,and PAm Pt could release Amp in response to the low p H in biofilms.The alleviation of the anoxic environment and the release of Lut increase the bacterial sensitivity to antibiotics.Confocal laser results show that TPGS-containing liposomes greatly facilitate the penetration of NPs into biofilms.In vitro antibacterial and antibiofilm experiments show that PAm Pt@Lut-Lip/Tp could kill bacteria inside biofilms and maintaining the integrity of the biofilms,while biofilms were completely dispersed after PAm Pt@Lut-Lip/Rl treatment.Biofilm-infected catheters were implanted subcutaneously in mice and treated with PAm Pt@Lut-Lip/Tp.The antibacterial effect and histological analysis of the catheters and surrounding tissues show good bactericidal effect and few bacteria in the surrounding tissues.However,the number of bacteria in the surrounding tissue is much higher with mild inflammation after PAm Pt@Lut-Lip/Rl treatment,and blood routine analysis indicates much higher white blood cell levels.Therefore,the sensitivity of bacteria to antibiotics has been enhanced through alleviation of the anoxic environment and inhibition of the quorum sensing in biofilms,and bacteria have been killed without apparent breakage of the biofilm matrix and bacterial escape into surrounding tissue.This study demonstrates a novel strategy to treat biofilms.