Sensitive visual detection of illegally added captopril using a novel dual-mode fluorescence / colorimetric sensor...

The illicit addition of the antihypertensive drug captopril to healthcare products has raised serious public health concerns. In this study, a novel bimetallic metal organic framework (ZrFe MOF) intrinsically exhibited both fluorescence emission and peroxidase-like catalytic activity, enabling a dual-mode fluorometric/colorimetric sensor for captopril detection. Upon the introduction of captopril, a specific interaction between the carboxyl group of captopril and the amino group of the ZrFe MOF ligand significantly increased the fluorescence intensity at 460 nm. Simultaneously, the thiol group of captopril specifically inhibited the peroxidase-like oxidation of 3,3',5,5'-tetramethylbenzidine (TMB), thereby decreasing the intensity of the absorbance signal at 652 nm. On the basis of the dual response mechanism of fluorescence enhancement and colorimetric inhibition, a highly sensitive dual-mode sensor with intrinsic self-validation was constructed for the visual detection of captopril. The limits of detection (LODs) for the fluorescence, colorimetric modes and smartphone sensing were determined to be 0.33 μM, 0.22 μM and 0.27 μM, respectively. Furthermore, the reliable method was successfully used for the determination of captopril in human serum and healthcare products, offering a sensitive and efficient approach for onsite rapid screening of illegally added captopril.