Nitrogen-doped TiO2 Nanocrystals for Highly Sensitive Electrochemical Immunoassay of Carcinoembryonic Antigen.

Nitrogen-doped TiO2 nanocrystals (N-TiO2 NCs) were simply synthesized and then functionalized with streptavidin for highly sensitive electrochemical immunoassay of tumor marker. Scanning electron microscopy, transmission electron microscopy, static water contact angle, and cyclic voltametric measurement were adapted to examine the properties of N-TiO2 NCs and resultant immunosensor. The functionalized N-TiO2 NCs sensing platform shows high electrochemical conductivity, large surface area and excellent hydrophilicity. The features make them to produce high current response, capture more antibody molecules, and maintain the bioactivity of immobilized antibodies. By means of carcinoembryonic antigen (CEA) as model tumor marker, a wide linear range of 0.005-3 ng/mL and a low detection limit of 0.005 ng/mL (signal-to-noise ratio of 3) were achieved by the proposed CEA immunosensor. Furthermore, the resultant CEA immunosensor displays high specificity and was employed to determine CEA in clinical serum samples. [ABSTRACT FROM AUTHOR]