Ultrasensitive electrochemical immunosensor based on the signal amplification strategy of the competitive reaction of Zn2+ and ATP ions to construct a "signal on" mode GOx-HRP enzyme cascade reaction.

A GOx/HRP@ZIF-90 nanomaterial is proposed by coating GOx and HRP in ZIF-90 using a bio-simulated mineralization method to improve the tolerance of the enzyme to the external environment. In the detection process, the ZIF-90 is turned on under mild conditions by the competitive reaction of ATP with Zn2+ and imidazole-2-carboxaldehyde (2-ICA), and the electrical signal of the system is amplified by the enzyme cascade reaction of GOx and HRP. Finally, based on the signal amplification strategy of the competitive reaction between Zn2+ and ATP to construct a "signal on" mode, electrochemical immunosensor of GOx-HRP enzyme-linked cascade reaction was prepared. The proposed electrochemical immunosensor shows an excellent analytical performance when detecting CA-125, with good selectivity and stability, with a detection range of 0.1 pg mL-1-40 ng mL-1 and a detection limit of 0.05 pg mL-1. The test has been performed using chronoamperometry under a constant voltage of -0.4 V. The immunosensor also shows an excellent performance when analysing human blood samples. The recovery of the immunosensor is 97.94-101.8%, with a relative standard deviation of 3.7-6.1%. The proposed sensor provides a novel idea for clinical use of GOx and HRP enzymes and a new method for the clinical detection of tumor markers.