A dual-mode colorimetric and fluorescent sensing platform based on MnO₂ nanosheets for sensitive detection of...

The timely and accurate identification of Escherichia coli (E. coli) plays a pivotal role in controlling foodborne infections and safeguarding public well-being. We designed a dual-mode sensing strategy based on manganese dioxide nanosheets (MnO₂ NS) to detect E. coli through colorimetric and fluorescent methods. E. coli could catalyze the conversion of p-benzoquinone (BQ) to hydroquinone (HQ) via an enzymatic reaction. Subsequently, HQ reduced MnO₂ NS to Mn²⁺, leading to a decrease in the oxidase-like activity of MnO₂ NS towards 3, 3', 5, 5'-tetramethylbenzidine (TMB) and amplex red (AR). As a result, based on the changes in absorbance at 652 nm and fluorescence intensity at 582 nm, E. coli was detected in the ranges 1.0 × 10¹ - 1.0 × 10⁶ CFU/mL and 1.0 × 10¹ - 1.0 × 10⁸ CFU/mL, respectively. The limits of detection were 1 CFU/mL and 5 CFU/mL, respectively. Furthermore, this MnO₂ NS-based colorimetric and fluorescent sensing strategy enabled accurate detection of E. coli in spiked milk samples. In summary, the developed strategy demonstrates significant potential for practical applications in foodborne pathogen detection.