Evaluation of the Enzymatic Activity of Glucose Oxidase Immobilized on Multiwalled Carbon Nanotubes and on Controlled Pore Glass by Sequential Injection Analysis

ABSTRACT

The enzymatic activities of glucose oxidase immobilized on multiwalled carbon nanotubes and on controlled pore glass were evaluated. The evaluation was performed by optimizing a system of sequential injection analysis with amperometric detection using a 3-mm glassy carbon electrode as the working electrode. Glucose oxidase was immobilized on polyaniline-multiwalled carbon nanotubes using glutaraldehyde as a reagent. Transmission electronic microscopy showed the coupling of polyaniline on the multiwalled carbon nanotubes and the coupling of the enzyme on the polyaniline-multiwalled carbon nanotubes. The optimum values to determine the enzymatic activity of glucose oxidase on both supports by sequential injection analysis were 1 mmol L⁻¹ pH 6 phosphate buffer, 25°C, glucose injection volume of 10 µL, reaction flow rate of 0.16 mL/min, an enzymatic reactor of 1 cm length x 0.2 cm i.d., 35 U of immobilized enzyme, and 0.8 V as the applied potential. The results showed a conditional Michaeles-Menten constant () of 5.38 (±0.23) mmol L⁻¹ for the glucose oxidase-polyaniline-multiwalled carbon nanotube reactor and 1.30 (±0.06) mmol L⁻¹ for the glucose oxidase-controlled pore glass reactor. The conditional maximum velocities () were 2.42 (±0.8) and 2.06 (±0.06) produced H₂O₂ min⁻¹, respectively. The results suggest that the enzyme is more exposed to the substrate when it is immobilized on controlled pore glass.

KEYWORDS:

• Controlled pore glass
• glucose oxidase
• immobilization
• multiwalled carbon nanotubes
• sequential injection analysis

Acknowledgments

The authors are also grateful to Verónica Occelli de la Parra M.Sc., for her translation support.