Abstract
Direct electron transfer of hemoglobin (Hb) was realized by immobilizing Hb on a carboxyl functionalized multi-walled carbon nanotubes (FMWCNTs) and gold nanoparticles (AuNPs) nanocomplex-modified glassy carbon electrode. The ultraviolet-visible absorption spectrometry (UV-Vis), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) methods were utilized for additional characterization of the AuNPs and FMWCNTs. The cyclic voltammogram of the modified electrode has a pair of well-defined quasi-reversible redox peaks with a formal potential of −0.270 ± 0.002 V (vs. Ag/AgCl) at a scan rate of 0.05 V/s. The heterogeneous electron transfer constant (ks) was evaluated to be 4.0 ± 0.2 s−1. The average surface concentration of electro-active Hb on the surface of the modified glassy carbon electrode was calculated to be 6.8 ± 0.3 × 10−10 mol cm−2. The cathodic peak current of the modified electrode increased linearly with increasing concentration of hydrogen peroxide (from 0.05 nM to 1 nM) with a detection limit of 0.05 ± 0.01 nM. The apparent Michaelis-Menten constant (Kmapp) was calculated to be 0.85 ± 0.1 nM. Thus, the modified electrode could be applied as a third generation biosensor with high sensitivity, long-term stability and low detection limit.
Highlights
Direct electrochemistry of redox proteins immobilized on different electrodes has recently attracted great attention
Direct electron transfer of Hb was realized when it was immobilized on the nanocomplex-modified glassy carbon (GC) electrode
Fourier transform infrared (FTIR) spectra of functionalized multi-walled carbon nanotubes (FMWCNTs) by KBr pellets were cellected in the range of
Summary
Direct electrochemistry of redox proteins immobilized on different electrodes has recently attracted great attention These methods can provide a suitable model for understanding the electron transfer mechanisms in biological systems and to establish a foundation for fabrication of electrochemical biosensors and devices [1,2,3,4]. Several nano materials, including carbon nanotubes and nanoparticles of Au, Ag, TiO2, Fe3O4 or MnO2, have been applied in electrochemical studies of hemoglobin and other redox proteins [39]. Direct electron transfer of Hb was realized when it was immobilized on the nanocomplex-modified glassy carbon (GC) electrode. This electrode could be used as a high sensitivity hydrogen peroxide (H2O2) biosensor
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