Copper peroxide/ZIF-8 self-producing H2O2 triggered cascade reaction for amperometric immunoassay of carbohydrate antigen 19-9.

Generally, H2O2 is frequently adopted to improve analysis capabilities of various detection systems. However, the addition of H2O2 with relatively higher concentration can lower the bioactivity of antibodies or antigens and the sensing interface stability in most peroxidase and peroxidase-like immunosensors. In order to solve these issues, we designed a novel copper peroxide/ZIF-8 immunoprobe that can self-produce H2O2 to trigger a cascade reaction for the sensitive detection of carbohydrate antigen 19-9. Specifically, CP/ZIF-8 plays a key role as a "signal switch" in the immunosensor. In the presence of HCl, the structures of ZIF-8 and copper peroxide can be broken, producing Cu2+ and H2O2 and a subsequent Fenton-type reaction that generates •OH. The resulting •OH can induce the decomposition of 3-aminobenzeneboronic acid/poly (vinyl alcohol) (PVA) film on the electrode. Although the immunosensor initially showed little current signal due to the poor conductivity pf ZIF-8 and PVA, the current signal was significantly amplified by a HCl-triggered cascade reaction. Under optimal conditions, the immunosensor displayed a wide linear range from 0.0001 to 100 U mL-1 with an ultralow limit of detection of 53.5 µU mL-1 (S/N = 3) for carbohydrate antigen 19-9. Considering these advantages, namely self-producing H2O2 and easy operation, this strategy paves a new way to design other novel sensors.