Abstract Accurate and rapid quantification of cytokines in biofluids is crucial for early disease diagnosis, management, and prevention. However, it still remains challenging for existing sensors due to the broad dynamic range of cytokines and high interference from sample matrices. To overcome these challenges, electrochemical (EC) and field‐effect transistor (FET) dual‐mode biosensing is integrated on an extended‐gate carbon nanotube field‐effect transistor. This biosensor chip effectively eliminates direct contact between the device and the solution and employs independent signal readouts based on two distinct response mechanisms, thereby circumventing the limitations associated with conventional transistor biosensors. Selective detection of cytokine (e.g., Interferon‐γ, IFN‐γ) is achieved by the FET sensing mode (0.1 to 4000 pg mL −1 , with a limit of detection of 24.1 fg mL −1 ) and the EC sensing mode (0.4–2000 ng mL −1 ) at different concentration range. The feasibility of real sample analysis using the EC‐FET dual‐mode biosensor is confirmed by detecting salivary levels of IFN‐γ. The combination of EC and FET sensing modes not only provides high sensitivity and a wide response range (seven orders of magnitude) to accommodate various biological samples but also improves the reliability of detection results, which shows promising applications in biological analysis and early disease diagnosis.

Electrochemical and Field Effect Transistor Dual‐Mode Biosensor Chip for Label‐Free Detection of Cytokine Storm Biomarker with High Sensitivity within a Wide Range