Ferrocene-Based Zr/Ni Bimetal–Organic Frameworks for Ratiometric Aptamer Sensors Enabling Efficient Dopamine Detection

To meet the demand for highly sensitive detection of dopamine (DA) in the diagnosis of neurological diseases, this study developed a ratio-type electrochemical biosensor based on MXene-enhanced bimetallic conductive metal-organic frameworks (ZrNi-Fc MOF). The introduction of Ni significantly improved the conductivity and catalytic activity of ZrNi-Fc MOF. By directly employing electrochemically active 1,1'-ferrocenedicarboxylic acid as the ligand, not only was the inherent poor conductivity of MOFs overcome, but also a stable foundation for constructing a ratio-type electrochemical sensor was provided. The phosphate-modified DA aptamers were covalently anchored onto the surface of ZrNi-Fc via "Zr-O-P" bonds, effectively enhancing the sensor's selective recognition ability for DA in complex matrices. With its large specific surface area, excellent conductivity, and biocompatibility, MXenes provided an ideal platform for the loading of Apt/ZrNi-Fc. Under optimized conditions, the sensor exhibited a detection range for DA from 0.1 to 70 μM and a low limit of detection (LOD) of 0.07 μM. In practical serum sample testing, the sensor demonstrated excellent recovery rates (98.67-100.5%) with relative standard deviations (RSDs) of 1.8 to 4.8%, yielding reliable results. This approach offers a novel strategy for enhancing the signal stability and sensitivity of ratio-type electrochemical biosensors.