Study Of Electrochemical Detection Methods Of Escherichia Coli O157:H7 Based On Nanocomposites Materials

Based on the simple preparation of novel nanocomposites by“one-pot method”and the use of portable glucose meter,three simple,fast,sensitive,and low-cost methods for the detection of Escherichia coli O157:H7 have been developed.(1)Detection of Escherichia coli O157:H7 based on concanavalin A-invertase calcium phosphate nanoflower and glucose meterA spherical concanavalin(Con A)-invertase-calcium phosphate organic-inorganic nanoflower(CIP)was simply prepared by the"one-pot method"as a novel signal probe for detecting E.coli O157:H7.In CIP,concanavalin is combined with E.coli O157:H7,and the invertase promotes the conversion of sucrose to glucose,which is directly quantified using a portable glucose meter.The results show that the linear range of this method for E.coli O157:H7 was 10²?10⁷ CFU/m L.The detection limit was 82CFU/m L.The recovery in milk samples was between 97.5%and 105.4%.(2)Detection of Escherichia coli O157:H7 based on antimicrobial peptide-phosphate nanoflower and glucose meterSpecific antimicrobial peptide of E.coli O157:H7,magainins I as an organic component,magainins I-copper phosphate organic-inorganic nanoflower was prepared by a simple"one-pot method",and Fe₃O₄ was embedded in this nanoflower as"capture"probes(MMPs)for magnetic separation;Antimicrobial peptide crocopin P1 and invertase were used as organic components,and crocropin P1-invertase-calcium phosphate organic-inorganic nanoflower(PIPs)were prepared by a simple"one-pot method"and used as signal probes for this detection.In the presence of the target E.coli O157:H7,a sandwich structure of MMPs-target-PIPs was formed.After magnetic separation,the invertase in the signal probe hydrolyzed sucrose to glucose,and then quantified by portable glucose meter.Under optimal conditions,the concentration of E.coli O157:H7 can be determined in a linear range of 10 to 10⁷ CFU/m L with a detection limit of 10 CFU/m L.(3)Electrochemical aptasensor based on DNA nanostrucures signal amplification for detection of Escherichia coli O157:H7Herein,the stable cocoon-like DNA nanostructures synthesized by rolling circle amplification reactions and loaded with Hemin,which were used as electrochemical signal tags to amplify signals.First,the single-stranded DNA capture probes were modified on Au electrode via Au-S bond.The E.coli O157:H7 specific aptamer and capture probe formed ds DNA structures on the Au electrode.In presence of E.coli O157:H7,aptamer preferentially binds to E.coli O157:H7,causing dissociation of some aptamer-capture probe,and releasing some capture probes.Subsequently,the free capture probe could hybridize with the DNA nanostructures through complementary DNA sequence.Under optimal conditions,the change in electrochemical signal was proportional to the logarithm of E.coli O157:H7 concentration,from 10¹ and 10⁶CFU/m L,and the detection limit was calculated to be 10 CFU/m L.