Fabrication of Au/ZnO/MWCNTs electrode and its characterization for electrochemical cholesterol biosensor
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RESEARCH
Fabrication of Au/ZnO/MWCNTs electrode and its characterization for electrochemical cholesterol biosensor Davood Ghanei Agh Kaariz1 · Elham Darabi1 · Seyed Mohammad Elahi1 Received: 16 July 2020 / Accepted: 9 August 2020 © Islamic Azad University 2020
Abstract In this work, a new sensitive enzyme-based electrode for electrochemical cholesterol biosensor was fabricated based on a nanocomposite of Au nanoparticles, ZnO nanoparticles and multi-wall carbon nanotubes (Au/ZnO/MWCNTs). The nanocomposite was prepared by sol–gel method and deposited on FTO substrate by dip coating, followed by cholesterol oxidase (ChOx) enzyme immobilized (ChOx/Au/ZnO/MWCNTs). Structural properties and morphology of the nanocomposite have been studied using X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM). The sample was subjected to Fourier transform infrared spectroscopy (FTIR) to determine functional groups. Electrochemical behavior of the electrode was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques as a function of cholesterol concentration. Electrochemical impedance spectroscopy (EIS) was also considered to study of surface modified electrodes. The ChOx/Au/ZnO/MWCNTs electrode has been found to have enhanced electron transfer and display excellent analytical linear performances. The fabricated electrode exhibited low detection limit (0.1 μM), high sensitivity (25.89 μA/ μM) evaluated from DPV data in the detection range of 0.1–100 µM and high selectivity in the determination of cholesterol over glucose and uric acid. The application of the ChOx/Au/ZnO/MWCNTs electrode in detection of cholesterol in human serum was also confirmed. Keywords Electrochemical biosensor · Cholesterol · Cholesterol oxidase · Au nanoparticles · ZnO nanoparticles · Multiwall carbon nanotubes · Au/ZnO/MWCNTs nanocomposite
Introduction Cholesterol (C27H46O) is one of the most important biomolecules and is one of the essential components of body. Its major role is to provide strength and flexibility to the biological membrane of cells and is present in several nerve tissues, brain and also serves as a source for preparation of fatty acids. Despite the undeniable importance of cholesterol, the excessive amounts of it can be dangerous for human health. The maximum amount of cholesterol in healthy human serum should not be more than 200 mg/dL (5.17 mM) [1]. The presence of excess cholesterol in the blood serum causes arteriosclerosis, which can lead to heart disease, arterial obstruction, kidney disease, and myocardial infarction. On the other hand, low levels of cholesterol in the * Elham Darabi [email protected] 1
Department of Physics, Faculty of Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran
blood can lead to anemia. Therefore, cholesterol level in the blood serum is one of the important parameters that should always be under control. Today, there is a great interest to find an exact, simple and user friendly method to determine cholestero
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