Dual-aptamers labeled polydopamine-polyethyleneimine copolymer dots assisted engineering a fluorescence biosensor for sensitive detection of Pseudomonas aeruginosa in food samples

To ensure the food security and protect public health, development of rapid and reliable approaches to detecting foodborne pathogens is of great significance. In this study, polydopamine-polyethyleneimine (PDA-PEI) copolymer dots are prepared via the self-polymerization of dopamine and cross-linking with branched PEI at room temperature. The PDA-PEI copolymer dots are very stable against photobleaching, extreme pH, as well as high ionic strength. They are used as a fluorescent probe to fabricate a biosensor for rapid and sensitive detection and quantification of Pseudomonas aeruginosa (P. aeruginosa). In the biosensor, dual-aptamers of P. aeruginosa are used to label PDA-PEI copolymer dots. Compared to single aptamer labeled PDA-PEI dots, the dual-aptamers labeled PDA-PEI dots endow the biosensor with enhanced sensitivity for target pathogen. The fluorescence biosensor demonstrates a wide linear response to P. aeruginosa in the concentration range of 10¹-10⁷ cfu mL^-1 with acceptable selectivity. The limit of detection is calculated to be 1 cfu mL^-1. The whole detection process can be finished in 1.5 h. The feasibility of the fabricated biosensor is verified by successful determination of P. aeruginosa in skim milk, orange juice, and popsicle samples. The biosensor provides an alternative and attractive platform for rapid and sensitive detection of bacteria in food products.