Colorimetric Detection of Salmonella typhimurium Based on Hybridization Chain Reactions and Aptamer
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Abstract:
A label-free, enzyme-free, and sensitive colorimetric detection method of Salmonella typhimurium (S. typhimurium) detection was proposed based on the recognition mechanism of the aptamer and the amplification strategy of hybridization chain reactions (HCRs) using the color variations of gold nanoparticles (AuNPs) as the colorimetric signals. An initiator and two hairpin probes in the HCR system were designed based on the aptamer of S. typhimurium. The aptamer binds to S. typhimurium DNA, thereby triggering the initiator to open the hairpin probes. This way, HCRs are initiated. While achieving the signal amplification for the target bacteria, the differences in the binding of the sticky ends of the hairpin probes before the reaction and the hybrid long chain formed after the reaction with gold nanoparticles was used to obtain the colorimetric signals, which results in rapid detection of S. typhimurium. Experimental parameters, such as the hybridization chain reaction time, binding time of the hairpin probes with gold nanoparticles, and concentrations of hairpin probes, have been optimized to improve the detection sensitivity. Under the optimal conditions, the logarithmic value of the S. typhimurium concentration and UV absorbance ratio (A630/525) exhibited a good linear relationship in the range of 103~107 CFU/mL. The detection limit equals 6.3×101 CFU/mL, and the spike recovery rate for milk samples ranges between 90.05%~109.97%. The proposed colorimetric method is easy and simple, and it does not require any chemical modification and complicated equipment. Furthermore, the experimental results are visible. This research provides a new method for rapid detection of S. typhimurium.
