Reduced graphene oxide–titania based platform for label-free biosensor

Abstract

A label-free biosensor has been fabricated using a reduced graphene oxide (RGO) and anatase titania (ant-TiO₂) nanocomposite, electrophoretically deposited onto an indium tin oxide coated glass substrate. The RGO-ant-TiO₂ nanocomposite has been functionalized with protein (horseradish peroxidase) conjugated antibodies for the specific recognition and detection of Vibrio cholerae. The presence of Ab-Vc on the RGO–ant-TiO₂ nanocomposite has been confirmed using electron microscopy, Fourier transform infrared spectroscopy and electrochemical techniques. Electrochemical studies relating to the fabricated Ab-Vc/RGO–ant-TiO₂/ITO immunoelectrode have been conducted to investigate the binding kinetics. This immunosensor exhibits improved biosensing properties in the detection of Vibrio cholerae, with a sensitivity of 18.17 × 10⁶ F mol⁻¹ L⁻¹ m⁻² in the detection range of 0.12–5.4 nmol L⁻¹, and a low detection limit of 0.12 nmol L⁻¹. The association (k_a), dissociation (k_d) and equilibrium rate constants have been estimated to be 0.07 nM, 0.002 nM and 0.41 nM, respectively. This Ab-Vc/RGO–ant-TiO₂/ITO immunoelectrode could be a suitable platform for the development of compact diagnostic devices.