Abstract:Objective To develop a label-free and visual colorimetric assay for the rapid detection of bisphenol A (BPA) using a BPA aptamer as the recognition molecule and metal-organic framework (Fe-MIL-101) nanozyme mimics as the signal probe.Methods The BPA aptamer was added to the Fe-MIL-101 solution, where it was adsorbed onto the Fe-MIL-101 surface through electrostatic interactions, thereby inhibiting the activity of nanozyme mimics. In the presence of BPA in the test sample, the aptamer specifically binds to BPA and detaches from the Fe-MIL-101 surface, restoring the catalytic activity of Fe-MIL-101. This enables Fe-MIL-101 to catalyze a colorless peroxidase substrate, generating a colorimetric output signal. The qualitative and quantitative analysis of BPA was achieved by monitoring the changes in the colorimetric signal.Results Under optimized conditions, the linear detection range for BPA in a buffered solution was 1~80 ng/mL, with a naked-eye visual detection limit of 0.5 ng/mL. When applied to BPA detection in milk and milk powder, the method achieved spike recoveries ranging from 83.6% to 95.2%, with relative standard deviations (RSDs) between 2.96% and 7.45%.Conclusion This method is simple, rapid, and highly accurate, demonstrating strong potential for practical applications.