pH-switchable dual-mode colorimetric-electrochemical aptasensor utilising cu@C-AuNPs nanozyme for the detection of aflatoxin B1 in food

Carbon material derived from lotus petiole exhibits enzyme-like activity. • The multiple enzyme-like activities of Cu@C-AuNPs can be switched by pH. • A colorimetric-electrochemical dual-mode aptasensor was successfully constructed. • The sensor provides a detection limit as low as 4.35 × 10 −6  ng mL −1 . • The developed method is suitable for controlling AFB1 in rice. Rapid and reliable detection of aflatoxin B1 (AFB1) is of paramount significance for food safety control and public health protection. Herein, a novel lotus petiole-derived pH-switchable Cu@C-AuNPs nanozyme featuring versatile enzyme-like activities was rationally engineered to fabricate a dual-mode colorimetric-electrochemical aptasensor for the ultrasensitive and selective detection of AFB1. Benefiting from its sharp pH-switchable catalytic behavior, the as-prepared nanozyme displays prominent peroxidase-like activity under acidic conditions (pH 4.0), efficiently catalyzing H 2 O 2 -mediated oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to enable visual colorimetric readout; in contrast, it switches to distinct catalase-like activity under neutral conditions (pH 7.4), decomposing H 2 O 2 to generate oxygen and thereby producing quantifiable electrochemical signals. Under optimized experimental parameters, the colorimetric mode exhibits a linear response from 1 × 10 −2 to 1 × 10 3  ng mL −1 with a limit of detection (LOD) of 6.96 × 10 −3  ng mL −1 , whereas the electrochemical mode achieves a broader linear range of 1 × 10 −5 to 1 × 10 3  ng mL −1 with a superior LOD of 4.35 × 10 −6  ng mL −1 . This dual-signal sensing strategy not only furnishes a robust and accurate platform for AFB1 detection but also holds promising application prospects in on-site and laboratory-grade food safety monitoring. A lotus petiole-derived Cu@C-AuNPs nanozyme with pH-switchable activities enables dual-mode detection of aflatoxin B1. At pH 4.0 (colorimetric), peroxidase-like activity oxidizes TMB to oxTMB, giving an absorbance increase (LOD 6.96 × 10 −3  ng mL −1 ). At pH 7.4 (electrochemical), catalase-like activity decomposes H 2 O 2 to O 2 , producing a current decrease (LOD 4.35 × 10 −6  ng mL −1 ). This aptasensor provides reliable cross-validation for food safety monitoring. Download: Download high-res image (177KB) Download: Download full-size image