A new hybrid nanocomposite electrode based on Au/CeO2-decorated functionalized glassy carbon microspheres for the voltammetric sensing of quercetin and its interaction with DNA

A new hybrid composite contains cerium oxide nanoparticles (CeO2NPs) and gold nanoparticles (AuNPs) decorated functionalized glassy carbon microspheres (FGCM) was synthesized (Au/CeO2@FGCM). As a result, the Au/CeO2@FGCM-paraffin oil paste electrode (PE) (Au/CeO2@FGCM-PE) was fabricated and employed for voltammetric sensing of quercetin (QRT). The structure and surface morphology of Au/CeO2@FGCM were studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). Cyclic voltammetry (CV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) were employed for the investigation of the electrochemical behavior of the Au/CeO2@FGCM-PE. Under the optimum conditions, the SWV oxidation peak current showed a linear dependence on the QRT concentration in the range of 48 nM to 1.09 µM. The achieved limits of detection and quantitation were 0.37 nM and 1.22 nM, respectively. The Au/CeO2@FGCM-PE is reproducible, sensitive and stable as well as displayed anti-interference ability for various common interferents. The proposed method was also successfully applied for real sample analysis, QRT content extracted from natural sources was determined, and satisfactory results achieved. Furthermore, the interaction of QRT with salmon testes and calf thymus dsDNA (st-DNA and ct-DNA) on the Au/CeO2@FGCM-PE was studied by CV and SWV. The corresponding binding constant (K), surface concentration (Γ), and Gibbs free energy (ΔG°) were computed for the free QRT and the bound QRT–dsDNA complex. The calculated K values for QRT-ct-DNA and QRT-st-DNA complexes were found to be 6.24×105 M-1 and 3.63×105 M-1, respectively, which revealed that the QRT is strongly interacted with ct-DNA compared to that with st-DNA. The decrease in intensity of the QRT oxidation peak resulting from its interaction with dsDNA provides a chance to use QRT as a new indicator to analyze ct-DNA and st-DNA.