We engineered an ingenious fluorescent aptasensor for detection of Pseudomonas aeruginosa (P. aeruginosa) according to the DNA hybridization and fluorescence resonance energy transfer. In the absence of target bacteria, 5carboxyfluorescein-labeled complementary DNA (FAM-cDNA) hybridizes with the partial sequences of aptamer and the fluorescence of FAM can be quenched by graphene oxide quantum dots (GOQDs). Upon the addition of target bacteria, the aptamer as a biorecognition element is bound with P. aeruginosa specifically. FAM-cDNA prefers to hybridize with the aptamer, resulting in the desorption of FAM-cDNA from GOQDs, thus recovering the fluorescence of FAM. The aptasensor shows a wide linear response to P. aeruginosa in the concentration range of 1.28 × 10 3 −2.00 × 10 7 cfu/mL with acceptable selectivity. The detection limit is 100 cfu/mL. The whole process can be finished in 2 h. Moreover, the platform is successfully applied to detect P. aeruginosa in drinking water, orange juice, and popsicle samples.

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A fluorometric assay is described for the detection of the food pathogen Pseudomonas aeruginosa (P. aeruginosa). It is based on the hybridization of aptamer and fluorescein-labeled complementary DNA (FAM-cDNA) in combination with magnetic separation. In the absence of P. aeruginosa, FAM-cDNA is assembled on the surface of aptamer modified magnetic particles (MNPs) via hybridization between aptamer and cDNA. Upon addition of P. aeruginosa, FAM-cDNA is replaced by the bacteria and released from the MNPs since the aptamer preferentially binds to bacteria. After magnetic separation, the amount of bacteria can be quantified by determination of the fluorescence intensity (λexc/em = 494/525 nm) of the supernatant containing the released FAM-cDNA. This kind of assay allows for both selective enrichment and sensitive fluorometric determination of bacteria in a single step. The assay has a response to the logarithm of P. aeruginosa concentration that is linear in the range between 10 and 10 cfu·mL, with a detection limit as low as 1 cfu·mL. The detection process can be finished within <1.5 h. The feasibility of the assay was verified by detecting P. aeruginosa in spiked food samples. Graphical abstract Hybridization of aptamer and carboxyfluorescein labeled complementary DNA is combined with magnetic separation for detection of as low as 1 cfu·mL Pseudomonas aeruginosa. This kind of assay allows for both selective enrichment and sensitive fluorometric determination of bacteria in a single step.

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