Electrodeposition of Carbon Nanotubes−Chitosan−Glucose Oxidase Biosensing Composite Films Triggered by Reduction of p-Benzoquinone or H₂O₂

Abstract

We report here on the electroreduction of p-benzoquinone (BQ) or H2O2 as a new trigger for simple, fast, uniform, and controllable electrodeposition of chitosan (CS) hydrogels and biosensing nanocomposite films of CS, multiwalled carbon nanotubes (MWCNTs), and glucose oxidase (GOD). The multiparameter electrochemical quartz crystal microbalance (EQCM) based on crystal electroacoustic impedance analysis was used to dynamically monitor the deposition processes. When the EQCM Au electrode was immersed in a weakly acidic solution (here pH 5.1 acetic buffer) containing BQ (or H2O2) and CS, the proton consumption during BQ (or H2O2) electroreduction increased the local solution pH near the electrode surface and led to the deposition of CS hydrogel on the electrode surface at local pH near and above the pKa value of CS. The concentration of BQ (or H2O2) required for CS electrodeposition was theoretically evaluated based on an electrogenerated base-to-acid titration model and supported by experiments. Co-deposition of GOD and MWCNTs with the CS hydrogel was achieved, and the resulting MWCNTs-CS-GOD nanocomposite films were demonstrated for glucose biosensing. The MWCNTs-CS-GOD enzyme electrode prepared by BQ reduction exhibited a current sensitivity of 6.7 microA mM-1 cm-2 to glucose, and the linear range for glucose detection at 0.7 V vs SCE was from 5 microM to 8 mM, with a detection limit of 2 microM and a Michaelis-Menten constant of 6.8 mM. The BQ-electroreduction protocol exhibited the best sensor performance, as compared with H2O2-reduction and previously reported water-reduction values. The present protocol via electroreduction of a deliberately added oxidant that is accompanied by a local pH change is highly recommended for wider applications in pH-dependent deposition of other films.

Fabrication of Tyrosinase Biosensor Based on Multiwalled Carbon Nanotubes‐Chitosan Composite and Its Application to Rapid Determination of Coliforms

“…This was similar to the optimum pH reported for other Tyr biosensors [21,22]. In addition, the Chit matrix was unstable at pH value lower than 6.0 [34], which also result in the decrease of amperometric response of the biosensor in acid condition. So, pH 7.0 was selected for further research.…”

Direct electron transfer of glucose oxidase immobilized in an ionic liquid reconstituted cellulose–carbon nanotube matrix

“…The value is also lower compared to previously reports (6.8 mM [29] and 15.19 mM [30]), which indicates an enhanced enzyme affinity of GOx to glucose with the biocompatible microenvironment of the cellulose-MWCNT matrix.…”

Simultaneous Determination of Ascorbic Acid, Dopamine and Uric Acid with Chitosan‐Graphene Modified Electrode

“…It is soluble in the protonated form and insoluble in the deprotonated form. The pK a value of chitosan is approximately 6.5 [7,8]. Scheme 1 shows the molecular structure and the protonation -deprotonation reaction of chitosan with different length of molecular chain.…”