ABTS-Modified Multiwalled Carbon Nanotubes as an Effective Mediating System for Bioelectrocatalytic Reduction of Oxygen

Abstract

The ability of such a common redox mediator as 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) to undergo sorption on carbon surfaces is explored here to convert multiwalled carbon nanotubes (CNTs) into a stable colloidal solution of ABTS-modified carbon nanostructures, the diameters of which are approximately 10 nm (as determined by transmission electron microscopy). Subsequently, inks composed of fungal laccase (Cerrena unicolor) mixed with the dispersion of ABTS-modified CNTs and stabilized with Nafion, were deposited on glassy carbon and successfully employed to the reduction of oxygen in McIlvain buffer at pH 5.2. For comparison, the systems utilizing only ABTS-free CNTs and laccase as well as ABTS-modified CNTs did not show appreciable activity toward the oxygen reduction. The three-dimensionally distributed ABTS-modified CNTs are expected to improve the film's overall conductivity and to facilitate electrical connection between the electrode and the enzyme. The network film of ABTS-modified CNTs is rigid, and it is characterized by charge propagation capabilities comparable to the conventional redox polymers. The whole concept of utilization of CNTs modified with ultrathin films of redox mediators in the preparation of efficient bioelectrocatalytic films seems to be of general importance to electroanalytical chemistry and to the development of biosensors.

Enhanced direct electron transfer between laccase and hierarchical carbon microfibers/carbon nanotubes composite electrodes. Comparison of three enzyme immobilization methods

“…This three-dimensional composite material (3D-CNT/CMF) was recently fabricated [8] and utilized in bioelectrocatalysis of horseradish peroxidase (HRP) for H 2 O 2 reduction at +600 mV vs. Ag|AgCl [9]. The main advantages for using the 3D-CNT/CMF composite electrode as immobilization surface for laccase consists on: i) avoiding the use of a redox hydrogel film as matrix for the electronic communication between enzyme and electrode, thus eliminating additional limitations such as the electron hopping step [10] and a further drop in the cell potential [11][12][13]; and ii) reduction of the large number of interfacial cascades in-between the individual CNT produced when they are simply dropped onto a supporting electrode in presence or not of a mediator/crosslinking polymeric net [14][15][16], which requires extensive optimization protocols and characterization methods, such as SECM [17,18].…”

Immobilized redox mediators for electrochemical NAD(P)+ regeneration

“…Magnetic Fe 3 O 4 nanoparticles were treated with aminopropyltriethoxysilane and subsequently dropped on the PDC/GC electrode to form a composite film. This modified electrode showed an enhanced effective surface area and increased electrocatalytic activity towards the oxidation of NAD(P)H. Besides the oxidation of NAD(P)H, mediators have been immobilized for the reduction of oxygen (Ganesan and Ramaraj 2000;Karnicka et al 2008;Nogala et al 2006), the detection of hydrogen peroxide (Liu et al 1997;Siao et al 2011), or without any application relation (Pauliukaite et al 2009). …”

Performances of Enzymatic Glucose/O2 Biofuel Cells

“…(Habrioux et al, 2010) Previous studies have shown the interest lying in the use of ABTS 2-as redox mediator in combination with multicopper oxidases. One of them was carried out by Karnicka et al who have shown that wiring laccase to glassy carbon through a ABTS 2-/carbon nanotube system was a very efficient pathway to reduce molecular oxygen into water (Karnicka et al, 2008). The combination of ABTS 2-with BOD is also known to exhibit a high electrochemical activity towards oxygen reduction reaction (Tsujimura et al, 2001).…”