Diazonium Electrografting vs. Physical Adsorption of Azure A at Carbon Nanotubes for Mediated Glucose Oxidation with FAD‐GDH

Abstract

The electrochemical reduction of aryldiazonium salts is a versatile and direct route to obtain robust covalently-modified electrodes. We report here a comparative study of Azure-A modified carbon nanotube electrodes prepared by diazonium electrografting and by physical adsorption for bioelectrocatalytic glucose oxidation with fungal FAD-glucose dehydrogenase from Aspergillus sp. The electrografted and adsorbed electrodes exhibited different reversible electroactivity consistent with polymer-type and monomer-type phenothiazine surface assemblies, respectively. The electrografted Azure A electrodes exhibited superior mediated bioelectrocatalysis compared to the adsorbed Azure A electrodes. A more than 10-fold higher catalytic current up to 2 mA cm-2 at 0.2 V vs. Ag/AgCl together with a similarly low onset potential of-0.05 V vs. Ag/AgCl was observed at the electrografted electrodes. Faster estimated electron transfer kinetics and a +200 mV potential shift for the polymer-type redox couple vs. the adsorbed monomer-type couple underlines the favourable driving force for mediated electron transfer with the buried FAD active site for the diazonium-derived bioelectrode.

Monofunctional pyrenes at carbon nanotube electrodes for direct electron transfer H2O2 reduction with HRP and HRP-bacterial nanocellulose

“…5 mg of MWCNTs were first added to 2 mL of NMP in a sealed glass vial and the resulting suspension sonicated for 60-120 min to achieve a homogeneous dispersion. 20 µL of the MWCNT dispersion (2.5 mg mL -1 ) was subsequently drop-casted onto the GC electrode to obtain a densely and homogeneously coated MWCNT layer after drying, based on our previously reported method (Gross et al, 2020). The modified electrode was dried under vacuum for ca.…”

“…The MWCNT electrodes were obtained according to our reported strategy that allows the formation of highly stable and reproducible MWCNT coatings on GC electrodes with a film thickness of ca. 6 µm (Gross et al, 2020;Lalaoui et al, 2016). The pyrene-modified MWCNT electrodes were prepared by a simple immersion protocol using a DMF modifier solution with 5 mmol L -1 of the pyrene derivative, followed by rinsing to remove weakly adsorbed species (Section 2.4).…”

Computer-Aided Rational Construction of Mediated Bioelectrocatalysis with π-Conjugated (Hetero)cyclic Molecules: Toward Promoted Distant Electron Tunneling and Improved Biosensing

“…Benefited from modularized but diversified structures, π-conjugated (hetero)­cyclic molecules with tunable redox potentials constitute an important organic mediator class for manifold bioelectrocatalytic applications. − Hybridization of p-orbitals throughout the molecular system not only enhances the multi-electron/charge delocalization and mobility but also reinforces the coplanar effects on conjugated atoms with limited freedom of molecular motions ( e.g. , rotation, twisting, bending, etc.…”

Utilization of FAD-Glucose Dehydrogenase from T. emersonii for Amperometric Biosensing and Biofuel Cell Devices

“…Just in the last decade, several integrated configurations have been shown. 17 − 21 These systems were fabricated using electropolymerization of aniline 22 or entrapment techniques that include a polymeric backbone with an Os complex or quinones as redox mediators. 23 , 24 The developed systems enabled an efficient mediated electron transfer (MET) process between the FAD-GDH enzyme and the electrodes.…”

“…In the last several decades, FAD-GDH was isolated from different origins and further characterized. Just in the last decade, several integrated configurations have been shown. − These systems were fabricated using electropolymerization of aniline or entrapment techniques that include a polymeric backbone with an Os complex or quinones as redox mediators. , The developed systems enabled an efficient mediated electron transfer (MET) process between the FAD-GDH enzyme and the electrodes. FAD-GDH was also bioengineered to fit direct electron transfer (DET) processes.…”