An ultrasensitive biosensor for virulence ompA gene of Cronobacter sakazakii based on boron doped carbon quantum dots-AuNPs nanozyme and exonuclease III-assisted target-recycling strategy

This work presented an electrochemical biosensor for the detection of virulence outer membrane protein A ( ompA ) gene of Cronobacter sakazakii ( C. sakazakii ), which was based on the mimic peroxidase activity of boron doped quantum dots-Au nanoparticles (BQDs-AuNPs) and a signal amplification strategy of exonuclease III (Exo III)-assisted target-recycling (EATR). The electrochemical signal was come from the electrochemical reduction of H 2 O 2 by BQDs-AuNPs nanozyme. Due to the enhanced peroxidase-mimic electrocatalytic efficiency of BQDs-AuNPs and the EATR strategy, the biosensor showed a broad linear range (1.0 × 10 -15 – 1.0 × 10 -8 mol L -1 ) and a low limit of detection (LOD, 4.0 × 10 -17 mol L -1 ). The constructed biosensor could also be applied in direct detection of extracted DNA from C. sakazakii . A good linear relationship (7.8 – 7.8 × 10 6 CFU mL −1 ) between the logarithm concentration of C. sakazakii and electrochemical signal was obtained with a LOD of 2.6 CFU mL −1 . The biosensor was applied in the detection of impA gene segments in contaminated infant formula with recoveries ranged in 83.4 – 108.2%.