Harnessing bifunctional nanozyme with potent catalytic and signal amplification for innovating electrochemical immunoassay.

Nanozyme-based electrochemical biosensors have emerged as an alternative to enzyme-based biosensors for next-generation bioanalysis. However, potential antibody modifications limit the catalytic sites of the nanozyme, thereby reducing sensor sensitivity. Here, a sensitive method for determining carcinoembryonic antigen (CEA) was developed. It involved coupling a cascade enzyme - enzyme - like catalytic reaction using Fe - Co Prussian blue analog nanozymes with high peroxidase - like activity (79.42 U mg). Briefly, the transduction of biological signals to chemical signals was achieved through the strategy centered on catalytic electroactive probes. Thereafter, with the assistance of the microelectrochemical workstation, the output of signals was realized. The platform exhibited an ultra-wide range of 0.020-100 ng mL and a detection limit of 0.013 ng mL CEA, which was mainly attributed to the excellent peroxidase activity, good conductivity, and synergistic amplification of current signals of synthesized nanozymes. In addition, the modification-free features greatly reduced the complexity of the bioassay and significantly improves its portability and cost-effectiveness. Overall, this study advances the development of nanozymes and their electrochemical biosensing applications and is expected to extend to the development of miniaturized devices in direct detection environments.