A dual-mode sensing strategy for the detection of Malathion based on bimetallic nanozymes coupled with aptamers

Malathion (MLT) is an organophosphate insecticide with well-defined toxicity to the human body. Both short-term exposure to high doses and long-term exposure to low doses can impair human health. In this study, we developed a novel colorimetric and photothermal method for the detection of MLT using aptamer (Apt)-conjugated FeCu-metal-organic framework (FeCu-MOF) loaded with gold nanoparticles (AuNPs). FeCu-MOF possesses peroxidase-like activity, enabling it to catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB). This reaction yields blue oxidized TMB (oxTMB), which generates detectable colorimetric and photothermal signals. The Apt binds specifically to MLT, thereby altering the catalytic activity of the nanozyme. This method capitalizes on the high catalytic efficiency of the nanozyme and the specific recognition capability of the Apt, enabling sensitive and selective detection of MLT. It also exhibits excellent selectivity against other interfering substances. When testing spiked samples, colorimetric detection yielded satisfactory results: recoveries ranged from 98.1% to 107.4%, with a relative standard deviation (RSD) below 3.3%. Additionally, the recovery rates of MLT determined via photothermal detection are reported herein, with recoveries ranging from 92.1% to 106.5% and RSDs less than 5.2%. Overall, this work provides a simple, rapid, and sensitive strategy for MLT detection, which holds significant potential for practical applications in food safety and environmental monitoring.