ZIF-67/Bz-Mm-Tp-COF@PGE-Based Point-of-Care Electrochemical Sensor for the Simultaneous Detection of Dopamine and Uric Acid in Blood

Being biological markers of several cardiovascular and neurological diseases, the detection and maintenance of dopamine (DA) and uric acid (UA) concentrations in blood are significant. However, the development of an electrochemical sensor that provides strongly resolved signals for the simultaneous evaluation of a broad range of DA and UA is still a challenge. A pencil graphite electrode (PGE)-based electrochemical sensor was developed by integrating the electrocatalytic properties of zeolitic imidazolate framework (ZIF-67) with a benzidine-melamine-terephthalaldehyde covalent organic framework (Bz-Mm-Tp-COF) for the simultaneous detection of DA and UA via differential pulse voltammetry (DPV). ZIF-67 permitted strong catalytic activity due to the incorporation of cobalt, whereas the COF offered an extensive electrochemical surface area along with stabilizing the composite through π-π interaction. Taking advantage of both, the ZIF-67/Bz-Mm-Tp-COF composite exhibited a large specific surface area, efficient catalytic activity, and nitrogen-rich groups, leading to hydrogen bonding with analyte molecules. The structural morphology of the composite was substantiated by field emission electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), and zeta potential. Whereas, fabricated electrodes were electrochemically characterized via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). The ZIF-67/Bz-Mm-Tp-COF@PGE sensor demonstrated a wide linear dynamic range of 0.001-250 μM and 0.001-1200 μM for DA and UA, respectively, spanning both physiological and pathological concentration windows relevant to clinical monitoring. The limits of detection (LOD) were determined to be 0.3 and 0.6 nM for DA and UA, respectively, calculated at a signal-to-noise ratio of 3. This may be attributed to the high electroactive surface area and efficient charge transfer facilitated by the composite architecture. An anti-interference study assured the selectivity of the designed electrochemical sensor. Following the practical applicability, an outstanding recovery percentage (95.8-108.3%) was obtained for spiked blood samples.