Non-covalent functionalization of multi-walled carbon nanotubes with cytochrome c: Enhanced direct electron transfer and analytical applications

Abstract

This work reports the non-covalent functionalization (dispersion) of multi-walled carbon nanotubes (MWCNTs) with cytochrome c (Cyt c), the direct electron transfer (DET) after drop-coating deposition of MWCNTs-Cyt c dispersion on glassy carbon electrodes (GCE), and the analytical applications for the highly sensitive quantification of hydrogen peroxide. The dispersion and the resulting modified electrodes were studied by UV–visible spectroscopy, scanning electron microscopy, and electrochemical techniques. The drastic treatment for dispersing the MWCNTs (5.0min sonication in water with ultrasonic tip) produces a partial denaturation that facilitates the interaction of Cyt c with the CNTs and makes possible an efficient electron transfer between the heme group and the electrode. A critical analysis of the influence of different experimental conditions on the efficiency of the dispersion and on the performance of GCE modified with MWCNTs-Cyt c dispersion is also reported. The analytical parameters obtained with GCE/MWCNTs-Cyt c for the amperometric quantification of hydrogen peroxide at −0.100V were: sensitivity of (43±1)mAM−1cm−2, linear range between 1.0×10−6 and 1.6×10−4M, detection limit of 1.5×10−7M, reproducibility of 3.1% and repeatability of 3.4%. The biosensor was successfully used for the quantification of hydrogen peroxide in mouthwash and spiked milk samples.