Cubic CeO₂ implanted reduced graphene oxide-based highly sensitive biosensor for non-invasive oral cancer biomarker detection

Herein, we report a cerium oxide nanocubes (ncCeO₂)–reduced graphene oxide (RGO)-based nanocomposite for the detection of oral cancer biomarker, cytokeratin fragment-21-1 (Cyfra-21-1), using the electrochemical technique. Nanocomposite of ncCeO₂–RGO was prepared by the in situ reduction of graphene oxide (GO), in the presence of ncCeO₂, using hydrazine hydrate. Raman spectra confirmed the presence of ncCeO₂ in the matrix of RGO. The chemical composition of the ncCeO₂–RGO nanocomposite was determined by X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) studies have indicated the presence of crystalline ncCeO₂ and the amorphous nature of RGO. Thin films of ncCeO₂–RGO composites were spin coated onto the indium tin oxide (ITO) coated glass surface and used for the co-immobilization of specific antibody of Cyfra-21-1 by N-ethyl-N-(3-dimethyl aminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide (EDC–NHS) coupling chemistry. Electrochemical response studies were monitored by using the differential pulse voltammetry (DPV) technique in the range of 0.625 pg mL⁻¹ to 15 ng mL⁻¹. The best linear response was observed in the range of 0.625 pg mL⁻¹ to 0.01 ng mL⁻¹, with a low detection limit of 0.625 pg mL⁻¹. The sensitivity was found to be 14.5 μA ng⁻¹ mL cm⁻² with R² 0.98, which was an improvement compared to the results from previously reported work. This BSA/anti-Cyfra-21-1/ncCeO₂–RGO/ITO immunosensor shows selectivity towards Cyfra-21-1 in the presence of glucose, sodium chloride (NaCl), mucin 16 (MUC-16) and interleukin 8 (IL-8).