Optimising Electrical Interfacing between the Trimeric Copper Nitrite Reductase and Carbon Nanotubes

Area of Science:

• Biocatalysis
• Electrochemistry
• Nanomaterials Science

Background:

• Nitrite reductase (NiR) is crucial for nitrogen cycling and denitrification.
• Efficient immobilization of enzymes on electrode surfaces is key for biosensor development.
• Multi-walled carbon nanotubes (MWCNTs) offer excellent surface area and conductivity for enzyme immobilization.

Purpose of the Study:

• To immobilize copper-containing nitrite reductase (NiR) from Alcaligenes faecalis onto functionalized MWCNT electrodes.
• To investigate the immobilization mechanism and its impact on enzyme electrocatalytic activity.
• To achieve high-performance bioelectrocatalytic reduction of nitrite.

Main Methods:

• Functionalization of MWCNTs with adamantyl groups to promote hydrophobic interactions.
• Immobilization of NiR onto functionalized MWCNT electrodes.
• Direct electrochemistry to assess nitrite reduction activity and current density.
• Analysis of enzyme subunit behavior and electron-tunneling distance.

Main Results:

• Successful immobilization of NiR on functionalized MWCNTs, primarily via hydrophobic interactions.
• Achieved a high bioelectrocatalytic reduction current density of 1.41 mA cm⁻² at NiR's redox potential.
• Demonstrated that enzyme desymmetrization upon immobilization leads to independent electrocatalytic behavior of subunits.
• Corroborated findings with electron-tunneling distance dependence studies.

Conclusions:

• Functionalized MWCNTs provide an effective platform for NiR immobilization, enhancing bioelectrocatalytic performance.
• Hydrophobic interactions play a significant role in the enzyme-electrode complex formation.
• The desymmetrization of NiR trimers on MWCNTs unlocks enhanced and independent electrocatalytic activity of individual subunits.