Synergistic aptamer/molecularly imprinted polymer-driven fluorescence/colorimetric dual-mode sensor based on Au/ZIF-67 nanocomposites for ultrasensitive ochratoxin A detection.

A dual-mode fluorescent/colorimetric sensor is presented utilizing Au/ZIF-67 nanocomposites for an ultrasensitive ochratoxin A (OTA) detection. The system employs polydopamine-coated FeO nanoparticles (FeO@MIP) as magnetic recognition elements and aptamer/3,3',5,5'-tetramethylbenzidine (TMB)-functionalized Au/ZIF-67 nanocomposites (Apt/TMB/Au/ZIF-67) as dual-signal probes for both fluorescence and colorimetric detection. Through molecular imprinting-aptamer synergistic recognition, OTA binding induces the formation of sandwich-structured particles (FeO@MIP-OTA-Apt/TMB/Au/ZIF-67). Magnetic separation of these particles facilitates fluorescence measurements, while residual Apt/TMB/Au/ZIF-67 in solution permits simultaneous colorimetric detection. Crucially, fluorescence intensity increases while colorimetric absorption decreases proportionally with OTA concentration (0.5-25 ng mL⁻), enabling self-validating dual-mode detection without requiring reagent replacement. The platform achieves detection limits of 0.15 ng mL⁻ (fluorescence) and 0.13 ng mL⁻ (colorimetry). The sensor was successfully validated for OTA quantification in real food samples, demonstrating significant potential for food safety applications.