Study On The Specific Bactericidal Effect And Sensitive Detection Of Mannose-modified Polyethyleneimine On Escherichia Coli

Foodbome diseases caused by pathogenic microorganisms are the most important issues in food safety,and have a wide range of impacts.And the harm to public health is also the most direct and clear.As a common pathogenic bacteria in life,Escherichia coli is widely distributed in the natural world,so food is highly contaminated by it,easily leading to food poisoning.Therefore,it is of great significance to discover and design antibacterial materials with low toxicity and high efficiency,and to establish a simple,feasible and rapid method for the detection of E.coli,which is very important for preventing food from being contaminated by microorganisms and ensuring consumer safety.In this paper,mannose-modified polyethyleneimine was used as the research object to explore its specific antibacterial effect and selective detection of E.coli.The main research contents and results can be summarized as the following two aspects:1.Mannose-modificated polyethylenimine for specific antibacterial effect against Escherichia coliPolyethyleneimine(PEI)has antimicrobial activity against Gram-positive(Staphylococcus aureus,S.aureus)and Gram-negative(Escherichia coli,E.coli),but it possesses highly cytotoxic and the selective antimicrobial activity against S.aureus is obviously better than E.coli.Therefore,in order to reduce the cytotoxicity and improve the antibacterial activity against E.coli,we modified PEI by D-mannose through nucleophilic addition between primary amine and aldehyde group to get mannose-modificated polyethyleneimine copolymer particles(Man-PEI CPs).Because of the specific binding of mannose and E.coli pili,Man-PEI CPs possess good targeting ability towards E.coli.The antibacterial activity of PEI and Man-PEI CPs was investigated.Man-PEI CPs show specific and very strong killing capability against E.coli at a concentration of 10 μg/mL,which is 22-fold lower than the minimum bactericidal concentration of PEI(220 μg/mL).More importantly,the Man-PEI CPs show less cytotoxicity and excellent biocompatibility.The results indicate that Man-PEI CPs have a wide range of applications as a novel antibacterial material and provide a new idea for constructing a new antibacterial pathway.2.Mannose-modificated polyethylenimine for specific and sensitive detection of Escherichia coliIn this study,we used mannose-modified polyethyleneimine(Man-PEI CPs)with significant fluorescence property;meanwhile,the high-density mannose ligands on the surface of Man-PEI CPs provide good targeting ability toward E.coli pili.These two properties make it possible to construct a new assay for detecting E.coli using Man-PEI CPs as a fluorescent probe.In order to obtain a good detection effect,we examined molecular weight of PEI and different mass ratio(PEI:mannose)on the detection of E.coli,and obtained the best conditions.Finally,the change of fluorescence intensity showed a good linear relationship with the concentration of E.coli in the range of 5.0×102-1.0×108 CFU/mL,and the limit of detection(LOD)was 265 CFU/mL.In addition,Man-PEI CPs have good selectivity for the detection of E.coli.And Man-PEI CPs also exhibit good detection effect on E.coli in real samples including tap water,beer and human urine.This method is simple,low cost and selective,and has great potential in the specific labeling and detection of E.coli.