Detection Of Foodborne Pathogenic Bacteria Based On Nanocomposites,Portable PH Meter And Pregnancy Test Strips

Based on the multifunctional nanocomposites,handheld pH meter,and pregnancy test strips,two sensitive,fast,simple and low-cost methods for detecting foodborne pathogens have been developed:(1)Based on the organic-inorganic nanocomposites embedded with acetaldehyde dehydrogenase(ALDH)and a handheld pH meter for determination of Salmonella typhimurium.In this study,ALDH-embedded organic-inorganic nanocomposite was used as a signal amplification system,and a portable pH meter was used as a signal output method to achieve specific detection of Salmonella typhimurium(S.typhimurium).ALDH and specific aptamers to S.Typhimurium,as organic components,were embedded in organic-inorganic nanocomposites(AAC)as a biosensor signal label,integrating the functions of signal amplification and target recognition.Embedding the aptamer and Fe₃O4 nanoparticles into the organic-inorganic hybrid nanocomposite(FAC)by biomimetic co-precipitation is used to specifically capture the target S.typhimurium.In the presence of the target Salmonella typhimurium,a"FAC-target-AAC"sandwich structure is formed.ALDH in AAC can catalyze rapid oxidation of acetaldehyde into acetic acid,resulting in pH change with portable pH meter readout.The altered pH exhibited a linear relationship with the logarithm of S.typhimurium from 10²to 10⁸CFU/m L and detection limit of 46 CFU/m L.Therefore,the detection method has potential application in the rapid quantification and qualitative identification of pathogenic bacteria.(2)Pregnancy test strips combine hybrid chain reaction(HCR)and metal organic framework(MOF)for of E.coli O157:H7In this study,pregnancy test strips,HCR,and MOF were combined to achieve visual determination of E.coli O157:H7.In the presence of E.coli O157:H7,the aptamer attached to the surface of magnetic bead is recognized and bound by E.coli O157:H7,and the exposed probe captures seize biotin-labeled HCR double-stranded DNA,and HCR double-stranded DNA are labeled with a large number of MOFs.Human chorionic gonadotropin(h CG)and streptavidin(SA)are encapsulated in MOF by a simple method,and the obtained MHS nanocomposite can be directly detected by pregnancy test strips.The pregnancy test strips visually detect the MOF encapsulated with h CG,so as to achieve rapid,sensitive and specific detection of E.coli O157:H7.The gray value of detection line exhibited a linear relationship with the logarithm of E.coli O157:H7 from 103 to 107CFU/m L and detection limit of 103CFU/m L.Thus,the detection method has potential application in the diagnosis of pathogenic bacteria.