Fluorescence/visual aptasensor based on Au/MOF nanocomposite for accurate and convenient aflatoxin B1 detection

A dual-mode fluorescence/visual aptasensor was developed for straightforward and accurate determination of aflatoxin B1 (AFB1) based on an Au/metal-organic framework (Au/MOF) composite. Aptamer-modified Au/Fe₃O₄ (Apt/Au/Fe₃O₄) served as the recognition element, and Au/MOF modified with complementary chains and 3,3',5,5'-tetramethylbenzidine (cDNA/TMB/Au/MOF) acted as the fluorescence and visual probes. These components are integrated to form conjugates (Apt/Au/Fe₃O₄-cDNA/TMB/Au/MOF). Upon the introduction of AFB1, some cDNA/TMB/Au/MOF dissociated from Apt/Au/Fe₃O₄, enabling the use of detached probes for visual detection. The undecomposed conjugates were isolated magnetically for use in fluorescence detection. As the AFB1 concentration increases, the visual signal intensifies and fluorescence intensity diminishes. Thus, the proposed aptasensor achieves the simultaneous fluorescence and visual determination of AFB1, obviating the need for material and reagent substitutions. The detection limits were established at 0.07 ng mL^-1 for the fluorescence mode and 0.08 ng mL^-1 for the visual mode. The effectiveness of the aptasensor was further validated by quantifying AFB1 in real samples.