Dual-wavelength ratiometric immunosensor for Bacillus cereus: Oxidase-like MnO2-Au trigged “OFF-ON” detection strategy

Abstract

As an opportunistic pathogen, Bacillus cereus (B. cereus) has caused increasing emetic and diarrheal food poisoning, even fulminant hepatic failure and death case. Herein, a mimetic oxidase-mediated ratiometric fluorescence enzyme-linked immunosorbent assay (ELISA) was developed to detect B. cereus. In this system, 3D MnO2-Au nanoflowers with layered crystalline structure can oxidize o-phenylenediamine (OPD) to generate a fluorescence peak at 570 nm (I570, response signal), while blue carbon quantum dots (bCDs) display a fluorescence peak at 455 nm (I455, reference signal). Under the effect of fluorescence resonance energy transfer (FRET), the response signal increased while the reference signal was weakened. By using MnO2-Au as the mimetic oxidase to replace the horseradish peroxidase and associate with antibody in traditional ELISA, a linear relationship was established between the ratiometric fluorescence signal (I570/I455) and the logarithm of B. cereus concentrations in the range from 1.7 × 102 to 3.3 × 106 CFU/mL. Comparing with conventional sandwich ELISA, the detection time was shortened by 43 min and the sensitivity was improved by 5-folds, indicating that the proposed ratiometric immunoassay holds great potential as a rapid and convenient tool for sensitive screening of B. cereus.