On-site enrichment and detection of live Salmonella typhimurium using a bioluminescence sensor coupled with a hyperbranched aptamer probe-labelled stir-bars array

Live food-borne pathogens pose one of the most serious threats to public health, because they can proliferate rapidly. Detecting trace levels of live bacteria in food samples is very important yet challenging. In this work, a hand-held stir-bars array modified with hyperbranched aptamer probes (HAPs) was developed for specific sorptive extraction of Salmonella typhimurium (S.T) used as a model. The HAPs were fabricated by grafting many aptamer fragments containing an azide group on a DNA long-chain skeleton containing alkyne groups through the Cu(I)-catalysed alkyne-azide cycloaddition reaction (CuAAC). The prepared stir-bars array was rich in aptamers and could enrich greatly S.T. The enriched S.T were then digested by lysozymes to emit ATP that was detected by a portable bioluminescence sensor. Since the ATP amount was correlated with that of live bacteria, the detection of ATP could be used for quantifying live S.T. The HAP-labelled stir-bars array exhibited high extraction level (100-fold higher than a stir bar modified by single-stranded aptamer), speed (20 min) and sensitivity (limit of detection: 8 CFU/mL) towards S.T. Moreover, it could be reusable. The assay coupling a portable bioluminescent sensor and stir-bars array can be used for on-site detection of live food-borne pathogens in complex water samples.