Direct Electrochemistry of Cholesterol Oxidase Immobilized on PEDOT Functionalized Screen-Printed Electrodes

Abstract

To address the problems of high cost and cumbersome preparation process in the current construction of cholesterol biosensors, a third-generation electrochemical cholesterol biosensor with a facile preparation method, low cost, enhanced sensitivity, and wide linear range was investigated in this paper. The cholesterol biosensor was constructed by immobilizing cholesterol oxidase (ChOx) on a poly-3,4-ethylenedioxythiophene (PEDOT) modified screen-printed electrode (SPE). This study showed a very simple fabrication process. The electrodes were constructed only in three steps, including in situ electropolymerization of PEDOT, enzyme introduction and encapsulation of the nafion membrane. The successful modification of PEDOT was demonstrated by Energy Dispersive X-ray spectroscopy (EDX) and Fourier-Transform Infrared spectroscopy (FT-IR). The morphological characterization and electrochemical analysis showed that the presence of PEDOT not only provided more anchoring sites for immobilizing enzymes, but also its high electrocatalytic activity enabled direct electron transfer (DET) between the ChOx and the electrode surface. The linear range for the actual detection of cholesterol was 50–800 μM, the sensitivity was 1.34 μA mM−1, and the electrical signal was not affected by interfering substances such as uric acid, glucose, dopamine, and ascorbic acid. Therefore, the cholesterol biosensor constructed in this paper was expected to achieve large-scale applications.