Molecular wiring of glucose oxidase enzyme with Mn polypyridine complex on MWCNT modified electrode surface and its bio-electrocatalytic oxidation and glucose sensing.

Abstract

A simple method for molecular wiring of glucose oxidase (GOx) enzyme with a low cost Mn polypyridine complex, Mn(phen)2Cl2, carboxylic acid functionalized multiwalled carbon nanotube (f-MWCNT) and Nafion (Nf), which is useful for glucose oxidation and sensing application in pH 7 phosphate buffer solution, has been demonstrated. In the typical preparation, f-MWCNT, Mn(phen)2Cl2, Nafion and GOx solution/suspension were successfully drop-casted as layer-by-layer on a cleaned glassy carbon electrode and potential cycled using cylic voltametric (CV) technique. In this preparation procedure, the Mn(phen)2Cl2 complex is in-situ converted as a dimer complex, Mn2(phen)2(O)(Cl2). A cooperative interaction based on π-π, covalent, ionic, hydrophilic and hydrophobic are operated in the bioelectrode for molecular wiring and electron-transfer shutting reaction. The modified electrode is designated as GCE/f-MWCNT@Mn2(phen)2(O)(Cl2)-Nf@GOx. CV response of the bioelectrode showed a defined redox peak current signal at an apparent standard electrode potential, E°'=0.55V vs Ag/AgCl. Upon exposure of glucose, the modified electrode showed a current linearity in a range, 0-6mM with a current sensitivity value, 349.4μAmM-1cm-2 by CV and a current linearity in a window, 50-550μM with a current sensitivity, 316.8μAmM-1cm-2 at applied biased potential, 0.65V vs Ag/AgCl by amperometric i-t methods. Obtained glucose oxidation current sensitivity values are relatively higher than Os-complex based transducer systems.