Highly sensitive choline biosensor based on carbon nanotube-modified Pt electrode combined with sol-gel immobilization

Abstract

A novel amperometric choline biosensor has been fabricated with choline oxidase (ChOx) immobilized by the sol-gel method on the surface of multi-walled carbon nanotubes (MWCNT) modified platinum electrode to improve the sensitivity and the anti-interferential property of the sensor. By analyzing the electrocatalytic activity of the modified electrode by MWCNT, it was found that MWCNT could not only improve the current response to H₂O₂ but also decrease the electrocatalytic potential. The effects of experimental variables such as the buffer solutions, pH and the amount of loading enzyme were investigated for the optimum analytical performance. This sensor shows sensitive determination of choline with a linear range from 5.0×10^-6 to 1.0×10^-4 mol/L when the operating pH and potential are 7.2 and 0.15 V, respectively. The detection limit of choline was 5.0×10^-7 mol/L. Selectivity for choline was 9.48 μA · (mmol/L)^-1. The biosensor exhibits excellent anti-interferential property and good stability, retaining 85% of its original current value even after a month. It has been applied to the determination of choline in human serum.