Fluorescent aptasensor for detection of live foodborne pathogens based on multicolor perovskite-quantum-dot-encoded DNA probes and dual-stirring-bar-assisted signal amplification.

In this study, a fluorescent (FL) aptasensor was developed for on-site detection of live (S.T.) and (V.P.). Complementary DNA (cDNA) of aptamer (Apt)-functionalized multicolor polyhedral oligomeric silsesquioxane-perovskite quantum dots (cDNA-POSS-PQDs) were used as encoded probes and combined with dual-stirring-bar-assisted signal amplification for pathogen quantification. In this system, bar 1 was labeled with the S.T. and V.P. Apts, and then bar 2 was functionalized with cDNA-POSS-PQDs. When S.T. and V.P. were introduced, pathogen-Apt complexes would form and be released into the supernatant from bar 1. Under agitation, the two complexes reached bar 2 and subsequently reacted with cDNA-POSS-PQDs, which were immobilized on MXene. Then, the encoded probes would be detached from bar 2 to generate FL signals in the supernatant. Notably, the pathogens can resume their free state and initiate next cycle. They swim between the two bars, and the FL signals can be gradually enhanced to maximum after several cycles. The FL signals from released encoded probes can be used to detect the analytes. In particular, live pathogens can be distinguished from dead ones by using an assay. The detection limits and linear range for S.T. and V.P. were 30 and 10 CFU/mL and 10-10 CFU/mL, respectively. Therefore, this assay has broad application potential for simultaneous on-site detection of various live pathogenic bacteria in water.