Study On Lateral Flow Immunoassays For Detection Of Escherichia Coli O157:H7 And Salmonella Enteritidis Based On Novel Label-free Probes

Nowadays,Contamination of foodborne pathogens is still a major public health threat to countries all around the world.Among these pathogens,Salmonella enteritidis?S.enteritidis?and Escherichia coli O157:H7?E.coli O157:H7?are two types of the most common causes of recent outbreaks that affect millions of people annually.Therefore,the rapid detection of pathogens via point-of-care testing?POCT?is critical to food safety.In this work,tow novel LFIAs was constructed for ultrasensitive detection of S.enteritidis and E.coli O157:H7,respectively.The results of this paper are as follows:1. Construction and characterization of novel label-free LFIA based on surface positively charged nitrogen-rich carbon nanomaterials for rapid detection of S.enteritidis:in this work,an innovative label-free LFIA was proposed for the sensitive detection of S.enteritidis by introducing a new nanoparticles-bacteria-antibody sandwich strategy in the sensor.Surface positively charged nitrogen-rich carbon?p NC?nanomaterials,synthesized via calcination and etching reactions,were used as adsorbent to capture bacteria as well as for generating signals.In the presence of target pathogens,bacterial cells could combine with p NC through electrostatic interaction and hydrogen bonding,then the complex would be captured specifically by the anti-bacteria monoclonal antibody coated on the test line.With the accumulation of nanoparticles-bacteria,the color on T-line would be gradually deepened from nearly colorless to deep black.Under the optimal conditions,the p NC-based immunoassay could exhibit high sensitivity for target pathogens detection with a low limit of detection?LOD?of 10² cfu m L^-1.In addition,this novel LFIA had no cross-reaction with other foodborne pathogens,showing its excellent specificity.Furthermore,this system was validated preliminarily to screen S.enteritidis in different food samples of potable water,cole slaw cabbage,watermelon juice and purple cabbage with low LODs of 10²cfu m L^-1,10³cfu m L^-1,10³cfu m L^-1 and 10³cfu m L^-1,respectively.Taking advantages of simplicity,label-free,convenience,and sensitivity,the p NC-based LFIA has the application potential for pathogenic microorganisms monitoring in food safety and early clinical diagnosis fields.2. Construction and characterization of multi-readout and label-free LFIA based on functional Prussian blue nanomaterials for rapid detection of E.coli O157:H7:In this work,A type of functional nanozyme—mannose modified Prussian blue?man-PB?nanoparticle,was introduced as the recognition agent as well as signal indicator.In the presence of target pathogens,the man-PB could capture them efficiently owing to the target binding of man-PB with Fim H proteins in flagella of E.coli O157:H7.The nanoparticles-bacteria complex would then be immunocaptured specifically by the detection Mc Ab coated on the T-line,forming a characteristic blue band.Furthermore,apart from original signal intensity on the T-line,the peroxidase-like catalytic activity-driven generation of colorimetric signal could be used as another format of quantitation.Under the optimal conditions,this novel LFIA could exhibit high sensitivity for target pathogens detection with a low limit of detection?LOD?of 10² cfu m L^-1.In addition,this novel LFIA had no cross-reaction with other foodborne pathogens,showing its excellent specificity.Furthermore,this system was validated preliminarily to screen E.coli O157:H7 in different food samples of potable water,milk,watermelon juice and purple cabbage with low LODs of 10²cfu m L^-1,10²cfu m L^-1,10³cfu m L^-1 and 10³cfu m L^-1,respectively.Taking advantages of multi-readout,label-free,convenience,and sensitivity,the p NC-based LFIA has the application potential for pathogenic microorganisms monitoring in food safety field.