Novel Silver Nanocomposite Synergistically Combats Carbapenem-resistant Acinetobacter Baumannii

Objective:In the face of the abundant production of various types of carbapenemases,many bacterium developed resistance to imipenem seen as“the last line of defence”.Currently,global monitoring statistics of resistance manifested the infection rate of carbapenem-resistant Acinetobacter baumanni(CRAB)increased every year,and its treatment was regarded as the imperative problem.Based on the superior antimicrobial activity for silver nanoparticles against multifarious bacterial strains,we constructed the IPM@AgNPs-PEG-NOTA nanocomposite whose core was silver nanoparticle to tackle the current dilemma.By researching on the resistance-reversal function,and antibacterial effect and mechanism,it will provide the new and high-efficient antibacterial therapy strategy for the drug-resistance bacteria.Methods:Making various characterization experiments of nanoparticles to verify the successful construct,such as transmission and scanning electron microscopy,dynamic light scattering,fourier transform infrared spectrometry.In order to assess the antibacterial effect for IPM@AgNPs-PEG-NOTA,we used the time-growth monitoring method,dilution method,disk diffusion method,live/dead backlight bacteria assay and scanning electron microscopy.By observing the variation of oxidative stress and metabolism,we researched the antibacterial mechanism of IPM@AgNPs-PEG-NOTA.The crystal violet assay、XTT Staining Assay、confocal laser scanning microscopy and RT-q PCR were analyzed about the effect and mechanism against biofilm.We evaluated thebiocompatibilityandhemocompatibilityof IPM@AgNPs-PEG-NOTA via MTT assay,LDH cytotoxicity assay,Hemolytic experiment and apoptosis evaluation with flow cytometry.We assessed the IPM@AgNPs-PEG-NOTA influence on bacteria-host interaction by the bacteria count,cell morphology monitoring,apoptosis evaluation with flow cytometry and PI fluorescence assay.In vivo,we analyzed the therapeutic effect of IPM@AgNPs-PEG-NOTA against the mice of carbapenem-resistant A.baumannii Pneumonia.Results:1.Due to the acid-sensitive response,IPM@AgNPs-PEG-NOTA could release more imipenem and Ag~+in acidic infected microenvironment, which was benefit to killing CRAB.2.This silver nanocomposite not only induced bacteria to generate ROS and MDA,but also inhibited the enzymatic activity of F-ATPase and the produce of ATP,appearing the phenomenon of DNA damage and protein suppression.3.The silver nanocomposite downregulated the levels of omp A gene expression to prevent foramation of biofilms.4.IPM@AgNPs-PEG-NOTA prevented the interaction of CRAB and host cell,which decreased cell death induced by carbapenem-resistant Acinetobacter baumannii infection.5.IPM@AgNPs-PEG-NOTA regulated the releasing of proinflammatory cytokine and promoted the expression of VEGF and PECAM-1, therefore,it could accelerate the repair of infected tissues.6.IPM@AgNPs-PEG-NOTA had excellent biocompatibility and hemocompatibility,in addition,it produced fewer side effects.Conclusion:AgNPs-PEG-NOTA can protect the released imipenem from the hydrolysis of metallo-β-lactamases,thus this silver nanocomposite plays a role in resistance-reversal function.The silver nanoparticles and imipenem synergistically combat carbapenem-resistant Acinetobacter baumannii.In addition to,IPM@AgNPs-PEG-NOTA not only offers immune regulation and accelerates tissues repair in vivo but can also prevent the interaction of pathogens and hosts.Based on excellentbiocompatibilityandhemocompatibility,IPM@AgNPs-PEG-NOTA provides the novel and high-efficiency antibacterial strategy for the therapy of carbapenem-resistant Acinetobacter baumannii.There are 26 figures,10 tables,and 123 references.