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 HO 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 - 1.0 × 10 mol L) and a low limit of detection (LOD, 4.0 × 10 mol L). 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 CFU mL) between the logarithm concentration of C. sakazakii and electrochemical signal was obtained with a LOD of 2.6 CFU mL. The biosensor was applied in the detection of impA gene segments in contaminated infant formula with recoveries ranged in 83.4 - 108.2%.