Cholesterol Self-Powered Biosensor

Abstract

Monitoring the cholesterol level is of great importance, especially for people with high risk of developing heart disease. Here we report on reagentless cholesterol detection in human plasma with a novel single-enzyme, membrane-free, self-powered biosensor, in which both cathodic and anodic bioelectrocatalytic reactions are powered by the same substrate. Cholesterol oxidase was immobilised in a sol-gel matrix on both the cathode and the anode. Hydrogen peroxide, a product of the enzymatic conversion of cholesterol, was electrocatalytically reduced, by the use of Prussian blue, at the cathode. In parallel, cholesterol oxidation catalysed by mediated cholesterol oxidase occurred at the anode. The analytical performance was assessed for both electrode systems separately. The combination of the two electrodes, formed on high surface-area carbon cloth electrodes, resulted in a self-powered biosensor with enhanced sensitivity (26.0 mA M -1 cm -2 ), compared to either of the two individual electrodes, and a dynamic range up to 4.1 mM cholesterol.Reagentless cholesterol detection with both electrochemical systems and with the self-powered biosensor was performed and the results were compared with the standard method of colorimetric cholesterol quantification.

Cholesterol as a Promising Alternative Energy Source: Bioelectrocatalytic Oxidation Using NAD-Dependent Cholesterol Dehydrogenase in Human Serum

“…The j max is much higher than those reported with bioanodes based on mediated ChOx. 20,[27][28][29] The control experiment performed with denatured DH exhibited an oxidation background due to the ability (albeit inefficient) of Toray carbon paper to oxidize NADH at +300 mV (vs. SCE). This background represents approximately 16% of the catalytic current obtained with active DH.…”

“…Electrochemical methods.-All electrochemical measurements were conducted on a CH Instrument Inc. model 660e potentiostat at room temperature (19)(20)(21) • C). Experiments were conducted in 100 mM phosphate/citrate buffer (pH 7.5) containing 10% v/v Triton X-100 using a three-electrode setup that included a Toray carbon paper electrode (paraffin wax-coated) as the working electrode, a saturated calomel reference electrode (SCE) and a platinum mesh counter electrode.…”

Printed Electrochemical Instruments for Biosensors

“…The Prussian blue was deposited following a previously optimized protocol. 31 A mixture of FeCl 3 (5 mM) and of K 3 [Fe(CN) 6 )] (5 mM) in HCl 0.1 M and KCl 0.1 M was prepared fresh and left to react for 20 minutes in the dark. Following this, 2 μl of the solution was drop-cast onto the working electrode and left to react for further 15 minutes in the dark.…”

(Plenary) Printed Electrochemical Instruments for Biosensors

“…The Prussian blue was deposited following a previously optimized protocol (31). A mixture of FeCl3 (5 mM) and of K3[Fe(CN)6)] (5 mM) in HCl 0.1 M and KCl 0.1 M was prepared fresh and left to react for 20 minutes in the dark.…”