Development of cholesterol biosensor using Au nanoparticles decorated f-MWCNT covered with polypyrrole network

Abstract

Cholesterol forms the basic structural components in the biological membrane and is present in several nerve tissues, brain and also serves as a source for the preparation of fatty acids. The determination of cholesterol level is significant in clinical diagnosis for heart problems, thrombosis etc. In this work, we report an electrochemical cholesterol biosensor based on cholesterol oxidase (ChOx) enzyme immobilized on gold nanoparticles – functionalized – multiwalled carbon nanotube (MWCNT) – polypyrrole (PPy) nanocomposite modified electrode. The sensor was fabricated by a two-step approach wherein the Au NPs-f-MWCNT was prepared by wet chemical method followed by electropolymerization of pyrrole. PPy act as a support matrix to hold ChOx and the presence of Au-f-MWCNT increases the electrical conductivity. Cyclic voltammetry (CV) exhibits a decrease in current with increasing cholesterol concentration which arises due to the competing action of Triton X100 surfactant employed for the preparation of cholesterol solution. The AuNPs-f-MWCNT-PPy-ChOx/GCE showed a linear response from 2 × 10−3 to 8 × 10−3 M in amperometry with a sensitivity and detection limit of 10.12 µA mM−1 cm−2 and 0.1 × 10−3 M respectively. Further, the detection of cholesterol using impedance spectroscopy was also demonstrated. The reproducibility, stability and the validity of the sensor in biological samples were also examined. Keywords: Cholesterol sensor, Au nanoparticles, Polypyrrole network, Electrochemical sensor, Impedance spectroscopy