Electrochemical impedance immunosensor for sub-picogram level detection of bovine interferon gamma based on cylinder-shaped TiO2 nanorods

Bovine interferon gamma (BoIFN-γ) released by T cells plays very important roles in early diagnosis of Mycobacterium tuberculosis (MTB) infections and control of bovine tuberculosis. In this work, a label-free electrochemical impedance immunosensor is for the first time developed for highly sensitive determination of BoIFN-γ. Cylinder-shaped TiO2 nanorods are synthesized by a facile hydrothermal method, and show high surface area and good hydrophicility. The immunosensor is fabricated by the immobilization of BoIFN-γ monoclonal antibody on the TiO2 nanorods modified glassy carbon electrode. The prepared TiO2 and immunosensor are characterized using transmission electron microscopy, scanning electron microscopy, X-ray diffraction, contact angle measurement, cyclic voltammetry, and electrochemical impedance spectra. The BoIFN-γ concentration is measured through the relative increase of impedance values in corresponding specific binding of BoIFN-γ antigen and BoIFN-γ antibody. The relative increased impedance values are proportional to the logarithmic value of BoIFN-γ concentrations in a wide range of 0.0001 to 0.1 ng/mL with a low detection limit of 0.1 pg/mL. The developed BoIFN-γ immunosensor shows a 249-fold decrease in detection limit in comparison with current enzyme-linked immunosorbent assay. This study provides a new, simple, and highly sensitive approach for very potential application in early diagnosis of MTB infections and control of bovine tuberculosis.