Efficient streptavidin-functionalized nitrogen-doped graphene for the development of highly sensitive electrochemical immunosensor.

In this work, an efficient and universal streptavidin-functionalized nitrogen-doped graphene (NG) was for the first time proposed and used to develop a highly sensitive electrochemical immunosensor for the detection of tumor markers. Transmission electron microscopy, electrochemical impedance spectrum, static water contact measurement, and cyclic voltammetry were used to characterize the streptavidin-functionalized NG platform and immunosensor. The biofunctionalized NG showed excellent hydrophilicity, larger specific surface area, and high electrochemical activity. These properties of the platform enhanced the loading capacity of proteins, and retained the bioactivity of the immobilized proteins, and thus remarkably improved the sensitivity of the immunosensor. Using carcinoembryonic antigen (CEA) as model analyte, the proposed immunosensor demonstrated a wide linear range of 0.02-12ngmL with a low detection limit of 0.01ngmL. The CEA immunosensor could be applied to detect human serum samples with satisfactory results. The streptavidin-functionalized NG material provided an universal and promising platform for the electrochemical immunosensing applications.