One Step Electrode Fabrication for Direct Electron Transfer Cholesterol Biosensor Based on Composite of Polypyrrole, Green Reduced Graphene Oxide and Cholesterol Oxidase

A simple single-step fabrication of a novel biocomposite electrode was used for cholesterol sensing through direct electron transfer. The bio-composite was prepared by polypyrrole, green reduced graphene oxide (gRGO) and cholesterol oxidase (ChOx). The graphene oxide (GO) was "green" reduced, with the Paederia foetide (PFL) plant extract at 60 degrees C to improve its biocompatibility. The adherence of gRGO to the electrode surface was improved through its co-deposition during electro-polymerization of pyrrole. Interestingly, the enzyme ChOx also could be immobilized during this co-deposition process, resulting in one step biosensor fabrication. The optimization of electrochemical deposition parameters on glassy carbon electrode for this enzymatic bioelectrode (ChOx-gRGO-PPy/GCE) has resulted in excellent sensitivity (1095.3 mu A mM(-1) cm(-2)), wide linear range (0.01-6 mM), and low detection limit (3.78 mu M) of cholesterol. Also, the Dubinin-Radushkevitch (D-R) adsorption study revealed the occurrence of physisorption (epsilon=3.35) process in this bioelectrode, confirming diffusion-controlled reaction. Reproducibility of electrodeposition procedure, impeccable selectivity in the presence of interferrants, repeatability for multiple use and long-term stability for practical use were also ensured. This could be used to construct the cost-effective device for cholesterol diagnosis.