New Insights on Potentiometric Immunosensor at Carbon Fiber Microelectrode for Alpha‐Fetoprotein in Hepatocellular Carcinoma

Abstract Herein, we investigated the analytical features of potentiometric immunosensors for detection of alpha‐fetoprotein (AFP) in hepatocellular carcinoma at different electrodes, such as carbon fiber microelectrode (CFME) and carbon‐disk electrode (CDE), respectively. To construct such an immunosensor, anti‐AFP capture antibodies were first conjugated covalently onto the activated electrodes through typical carbodiimide coupling. Thereafter, one‐step immunoreaction protocol was successfully introduced to develop a new potentiometric immunoassay upon addition of AFP. Accompanying the antigen‐antibody reaction, the surface charges of the modified electrodes were changed for the readout of electric potential. Results indicated that the linear range of CDE‐based immunosensor was 0.1–100 ng mL −1 AFP, whereas the assay sensitivity by using CFME could be further increased to 3.2 pg mL −1 with the linear range from 0.01 to 500 ng mL −1 AFP. Meanwhile, CFME‐based immunosensor showed high sensitivity, good reproducibility and specificity, and could be utilized for the analysis of human serum specimens with consistent results relative to commercialized ELISA kit.