Electrochemically amplified nanozymatic activity of biolinker-based Co-MOF for H₂O₂ and dopamine detection

Rapid, sensitive and selective H₂O₂ and dopamine sensors provide enormous opportunities to health, food and environmental monitoring, which could prevent major social and economic losses. To overcome the sluggish response and low sensitivity of the conventional colorimetric assays, an electrochemical platform integrated with the conventional assay was proposed in this work. First, a microwave-assisted cobalt MOF (Co-MOF) was synthesized using a bio-linker and characterized using FESEM and TEM. The electrochemical performance of Co-MOF was examined through cyclic voltammetry (CV), where eight-fold higher currents were achieved for Co-MOF compared to those of the unmodified electrode. However, Co-MOF exhibits very weak nanozymatic activity in a mixture of 3,3',5,5'-tetramethylbenzidine (TMB) and H₂O₂. Integration of the superior electrochemical characteristics of Co-MOF with the nanozymatic activity resulted in a six-fold enhanced nanozymatic activity that enabled H₂O₂ quantification with a limit of detection (LOD) of 32 nM under optimized conditions. The modified electrode was further used to quantify dopamine, achieving an LOD of 0.81 µM, with a remarkably shorter detection time (60 fold shorter) compared to the conventional nanozyme. A mechanistic study showed that Co-MOF provides a large surface area and abundant redox-active sites, facilitating fast electron transfer and significantly enhancing the electrochemical signal.