An aptamer-integrated bimetallic MOF nanozyme for dual-mode colorimetric and fluorescence sensing of bisphenol A

As a representative endocrine-disrupting compound, bisphenol A (BPA) can leach from food packaging materials into food, thereby presenting potential risks to human health. Therefore, the development of rapid, sensitive, and reliable methods for BPA detection is of great importance. In this study, a dual-mode colorimetric/fluorescence aptasensor based on Cu/Zr-MOF nanozyme was developed for BPA detection, providing both colorimetric and fluorescence signal readouts. The aptasensor was immobilized on the Cu/Zr-MOF surface through coordination between Zr⁴⁺ sites and the phosphate group of the aptamer. Aptamer modification blocked the active sites of Cu/Zr-MOF, thereby suppressing its peroxidase-like activity and quenching the fluorescence signal in the Cu/Zr-MOF + TMB + H₂O₂ system. Upon exposure to BPA, the aptamer specifically recognized and bound BPA, leading to its dissociation from the Cu/Zr-MOF surface. Consequently, both the POD activity of Cu/Zr-MOF and the fluorescence intensity of the system were restored. Under optimal conditions, the aptasensor displayed linear ranges of 1-300 ng/mL (colorimetric) and 0.500-400 ng/mL (fluorescence), with detection limits of 0.084 and 0.053 ng/mL, respectively. This dual-mode design provided two signal outputs, thereby improving detection reliability over single-mode systems and enabling flexible mode selection based on the testing environment. The sensing system was further extended to paper-based test strips, affording linear ranges of 1-150 ng/mL for both modes and detection limits of 0.140 ng/mL (colorimetric mode) and 0.227 ng/mL (fluorescence mode). These results demonstrate that the proposed Cu/Zr-MOF@Apt sensing platform has promising potential for rapid on-site BPA detection in food safety and environmental monitoring applications.