Amine-Functionalized MoO₃@RGO Nanohybrid-Based Biosensor for Breast Cancer Detection

We report results of studies relating to development of an ultrasensitive, rapid, and label-free biosensor based on molybdenum trioxide (MoO₃) anchored onto the reduced graphene oxide (RGO) for breast cancer detection. The human epidermal growth factor receptor-2 (HER-2) secreted in the serum of breast cancer patients was used as an analyte for the detection. The in situ growth of 1D MoO₃ onto reduced graphene oxide (RGO), a 2D carbon substrate, was carried out via one-pot low-temperature hydrothermal synthesis. Subsequently, the surface conjugation of the monoclonal antibodies (anti-HER-2) onto the APTES/MoO₃@RGO/ITO electrode was conducted via EDC-NHS covalent chemistry. The structural and morphological properties of the MoO₃@RGO nanohybrid were investigated using electron microscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopic techniques. The surface area of the MoO₃@RGO nanohybrid determined via Brauner-Emmett-Teller analysis was found to be 14 times greater than that of the pristine MoO₃. The binding kinetics and the electrochemical activity of the developed platform were determined by cyclic voltammetry, differential pulse voltammetry, and impedance spectroscopic techniques. This nanohybrid based immunosensor exhibited improved sensitivity (13 uA mLng^-1cm^-2) in a broad concentration range (0.001-500 ng mL^-1) with a correlation coefficient of 0.98. The limit of detection of this MoO₃@RGO nanohybrid based immunosensor was found to be 0.001 ng mL^-1. The results obtained via the developed immunosensor for the quantification of serum HER-2 were validated using ELISA.