Different behaviors of single and multi wall carbon nanotubes for studying electrochemistry and electrocatalysis of choline oxidase

This work presents a detailed comparison between single and multi wall carbon nanotubes (SWCNTs & MWCNTs) in an effort to understand which could be a better supporting material for studying the electrochemistry and electrocatalysis of enzymes. Choline oxidase (ChOx) was chosen as a model enzyme for evaluation of the electrodes’ performance. The enzyme was adsorbed on either SWCNT or MWCNT modified electrode, in the presence of a typical room temperature ionic liquid (RTIL), and its electron transfer and electroanalytical response toward choline was investigated. RTIL/MWCNTs/GC electrode was uniformly covered by ChOx. Besides, higher electrical conductivity, better reversibility of the ChOx redox reaction and higher electron transfer rate of the enzyme indicated more facile and rapid rate of electron transfer. On the other hand, RTIL/SWCNTs/GC electrodes showed higher amount of enzyme loading, higher enzyme–substrate affinity, lower detection limit, better sensitivity and wider linear range. Consequently, MWCNTs are preferable for kinetic study of ChOx, while SWCNTs are more convenient for biosensing applications.

► In the presence of a typical room temperature ionic liquid (RTIL), Choline oxidase (ChOx) as a model enzyme was uniformly immobilized on either single or multi wall carbon nanotubes (SWCNTs or MWCNTs) covered on glassy carbon (GC) electrode, and the electron transfer and electroanalytical response of enzyme toward choline was evaluated.
► ChOx on RTIL/MWCNTs/GC electrode showed higher electrical conductivity, better reversibility of redox reaction and higher electron transfer rate indicating more facile and rapid rate of electron transfer.
► On the other hand, RTIL/SWCNTs/GC electrode showed higher amount of enzyme loading, higher enzyme-substrate affinity, lower detection limit, better sensitivity and wider linear range.
► Consequently, MWCNTs are preferable for kinetic study of ChOx, while SWCNTs are more convenient for biosensing applications.