Application of a printed electrocatalyst for H2O2 to the development of biosensors
Gonzalez-Macia, L. and Killard, A. (2012) Application of a printed electrocatalyst for H2O2 to the development of biosensors. In: Electrochem 2012, Dublin, Ireland, 2nd - 4th September, 2012.
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Many enzymatic reactions, e.g. the oxidation of glucose or cholesterol by glucose oxidase (GOx) or cholesterol oxidase (ChOx), respectively, in the presence of oxygen release hydrogen peroxide (H2O2) as an end-product. Therefore, the determination of its concentration may be used as an indicator in the progress of the reaction. Many metal and metal alloys such as Pt, Pd, Ag, Pd/Au and Au/Pt have been employed in recent years in the manufacture of electrochemical sensors for H2O2 determination. However, its slow electrocatalytic kinetics at metallic electrodes and the need for high applied potentials have prevented it from being more widely used as the signalling molecule in biological systems. Recently, our group has reported a significant enhancement in the catalytic activity of silver screen printed electrodes towards H2O2 reduction after exposure to a mixed surfactant/salt solution. The electrodes modified with a dodecylbenzenesulphonic acid (DBSA) and KCl solution exhibited up to 80-fold higher responses when H2O2 was measured by amperometry at -0.1 V vs. Ag/AgCl. The use of inkjet printing during the modification process might improve the variability of the sensing devices found in previous manual modification procedures by enhancing the control of the reagent volume and exposure times. In the present work, DBSA/KCl modified silver screen printed electrodes were assessed for their ability to couple this electrocatalysis to the reduction of H2O2 generated from enzymatic reactions. First, a mediatorless glucose biosensor was fabricated by the immobilization of GOx onto the modified electrode. The deposition of a perm-selective membrane of cellulose acetate was required to prevent interferences at the electrode surface as well as to facilitate enzyme immobilization. Then, the capacity of the electrocatalyst to detect the H2O2 produced after the enzymatic reaction of cholesterol oxidase and cholesterol was evaluated. Analytical parameters of the biosensors such as LOD, sensitivity and reproducibility were measured. The device was shown to be capable of the quantitative determination of both glucose and cholesterol.  L. Gonzalez-Macia, M.R. Smyth, A. Morrin, A.J. Killard, Electrochimica Acta, 2011, 56, 4146-4153.  L. Gonzalez-Macia, M.R. Smyth, A.J. Killard, Electroanalysis, 2012, 24(3), 609-614.