Medium-entropy nanoenzyme with high oxidase-like activity for sensitive detection of interleukin-6 based on ELISA.

Interleukin-6 (IL-6) is an acute phase response protein. Its level rapidly increases in infection, trauma, and acute inflammatory states. It usually appears earlier than other inflammatory markers such as C-reactive protein and procalcitonin. Therefore, detecting abnormal IL-6 levels (The clinical reference range is greater than 7 pg mL-1) faster can help humans receive timely treatment and recover their health. This article successfully synthesized a medium-entropy oxide nanoenzyme. It does not require the involvement of hydrogen peroxide and has a low Michaelis constant of 0.101 mM. Based on the interaction between La-based medium-entropy oxide (MEO-La) nanoenzyme and secondary antibody, specific detection of IL-6 in enzyme-linked immunosorbent assay is achieved. The concentration of IL-6 in human serum can be qualitatively detected. The detection limit and linear range are 0.03 pg mL-1 and 5-1000 pg mL-1, respectively. This work not only is of great significance for better understanding the unique properties of medium-entropy nanoenzymes but also has enormous potential for biochemical sensing of human health.