Portable electrochemical biosensor based on laser-induced graphene and MnO2 switch-bridged DNA signal amplification for sensitive detection of pesticide.

Developing portable, quantitative, and user-friendly analytical tools for sensitive pesticide assay is of significant importance for guaranteeing food safety. Herein, a novel electrochemical biosensor was constructed by integrating laser-induced graphene (LIG) electrode on polyimide (PI) foil and MnO2 nanosheets loaded on the paper for point-of-care test (POCT) of organophosphorus (OPs) residues. The principle of this biosensor relied on acetylcholinesterase (AChE)-catalyzed hydrolytic product-triggered disintegration of MnO2 nanosheets for releasing assistant DNA to initiate nicking enzyme-aided recycling amplification. In the presence of OPs, the activity of AChE was inhibited and could not initiate the cleavage of the electroactive molecules-labeled hairpin probe on the electrode, resulting in the maintenance of the electrochemical response to realize a "sign-on" determination of OPs. The proposed biosensor exhibited satisfactory analytical performance for OPs assay with a linear range from 3 to 4000 ng/mL and a limit of detection down to 1.2 ng/mL. Moreover, the biosensor was useful for evaluating the residual level of pesticides in the vegetables. Therefore, this novel biosensor holds great promise for OPs assay and opens a new avenue on the development of higher-performance POCT device for sensing applications in the environment and food safety fields.