Development of a biosensor for HDL-cholesterol based on a novel electrocatalyst for hydrogen peroxide reduction
Ahmadraji, T. , Gonzalez-Macia, L. and Killard, A. (2012) Development of a biosensor for HDL-cholesterol based on a novel electrocatalyst for hydrogen peroxide reduction. In: Electrochem 2012, Dublin, Ireland, 2nd - 4th September, 2012.
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Cholesterol is synthesized in the liver and transported in the blood in association with low density lipoprotein (LDL-C) and high density lipoprotein (HDL-C). HDL-C is a modifiable risk for coronary heart disease. Its routine measurement is recommended in the evaluation and management of hypercholesterolemia. In the past three decades, chemical precipitation methods, and more recently, homogeneous assays have been used to measure plasma HDL-C in clinical laboratories. Homogeneous assays were a major step forward in improving the precision of earlier precipitation methods. The final step of measurement is typically based on the formation of hydrogen peroxide from cholesterol oxidase (ChOx). Novel methods for the electrocatalytic reduction of hydrogen peroxide have been developed .Ref It has been shown that polyoxyethylene alkylene tribenzylphenyl ethers allow HDL-C to be selectively dissolved to allow the enzymatic catalysis of HDL-C alone.Ref This work is investigating the application of homogeneous cholesterol assay strategies to the measurement of HDL-C in combination with this novel electrochemical transduction methodology. Printed electrodes with good catalysis of hydrogen peroxide at moderate reduction potentials were evaluated as the basis of the assay.Ref The effects of assay reagents such as buffer and surfactant on the electrode behaviour were assessed amperometrically in the presence of hydrogen peroxide solutions. Of three buffers evaluated, the electrodes showed a linear responses in 0.1M PBS (pH=6.8) with enhanced catalytic activity toward H2O2 in presence of Emulgen B-66. The effect of other assay components such as cholesterol oxidase, cholesterol esterase and serum components were measured using the modified electrodes. However, the serum components showed a negative effect on electrode behaviour. Amperometric response in 0 to 2.5 mM HDL-C solutions were also measured. Non-specific signal contributions were observed from assay components. Further method development is to be performed to eliminate these interferences. In order to understand the mechanism and kinetics of the reaction, the spectroscopic studies were carried out at room temperature using cholesterol and cholestry acetate stock solutions. An enzymatic inhibition was observed at Cholesteryl acetate concentration above 2mM.
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