The Biosensor For Salmonella Detection Based On The Technology Of Restriction Endonuclease Amplification

In this paper, the harmness, classification and the research status of food-borne pathogens have been introduced. The function and characteristics of the aptamer have been used in biosensor for detection. Endonuclease amplification technology has been used in biosensor. And the function and characteristics of the aptamer have been improved, which was used for detection of food-borne pathogens.We have designed a simple, time-saving, one step in the detection of Salmonella typhimurium fluorescence biosensor based on the specificity of recognition and adsorption function of aptamer. Aptamer-primer probe(arched probe) containing anti-target aptamer and a primer sequence, which is released under the challenging of target, is used for recognizing target and triggering strand displacement amplification based polymerase elongation. And a hairpin(HP) was also designed, which was modified with FITC and quencher at the 3 'end and the 5' end respectively. The target pathogen, S. Typhimurium, associates with the aptamer sequences and the released primer unfolds the hairpin structure of the probes, leading to the production of fluorescence. At the same time, a recycle of the primer and a continuous production of primer sequences(assisted by phi29 polymerase and Nb.BbvCI endonuclease) were achieved. Under optimal conditions, the proposed biosensor exhibits ultrahigh sensitivity toward S. Typhimurium with detection limits of 600 cfu mL-1 within 2 h. Hence, the fluorescence based method might create a useful and practical platform for detecting pathogenic bacteria and related food safety analysis.In the work, a simple, isothermal, and ultrasensitive homogeneous colorimetric sensor for pathogenic bacteria detection has been developed on the basis of target-triggered exponential amplification reaction(EXPAR). Aptamer-primer probe(arched probe) containing anti-target aptamer and a primer sequence, which is released under the challenging of target, is used for recognizing target and triggering EXPAR-based polymerase elongation. Due to EXPAR coupled DNAzyme amplification strategy, the presence of target pathogenic bacteria leads to the formation of numerous G-quadruplex oligomers in solution, which folds into G-quadruplex/hemin complexs with the help of K+ and hemin, thus generating extremely strong catalytic activity toward H2O2 and giving a remarkably strong UV-vis absorption. This work is a novel design that EXPAR coupled DNAzyme amplification technique has been integrated into colorimetric assay for detecting pathogenic bacteria. Under optimal conditions, the proposed biosensor exhibits ultrahigh sensitivity toward target pathogenic bacteria with detection limits of 80 cfu mL-1. Besides, our biosensor also shows high selectivity toward target pathogenic bacteria and has the advantages in its low cost, simplified operations without the need of labeling steps and additional labile reagents. Hence, the EXPAR coupled DNAzyme amplification-based colorimetric method might create a useful and practical platform for detecting pathogenic bacteria and related food safety analysis and environmental monitoring.