A novel nitrite biosensor based on direct electron transfer of hemoglobin immobilized on a graphene oxide/Au nanoparticles/multiwalled carbon nanotubes nanocomposite film

Abstract

A novel nitrite biosensor was fabricated by immobilizing a graphene oxide–hemoglobin composite hydrogel (GO–Hb) on an Au nanoparticles/multiwalled carbon nanotubes composite film modified glassy carbon electrode (AuNPs/MWCNTs/GCE). The GO–Hb/AuNPs/MWCNTs composite film was characterized by electrochemistry, scanning electron microscopy and UV-vis spectroscopy. The results showed that the Hb in GO–Hb composite hydrogel retained its native structure. Cyclic voltammetry of the GO–Hb/AuNPs/MWCNTs composite film displayed a pair of well-defined and quasireversible redox peaks, which indicated that direct electron transfer of Hb was realized in the hybrid modified electrode. The charge transfer coefficient (α) and the electron transfer rate constant (k_s) were calculated to be 0.473 and 2.61 s⁻¹, respectively, which illustrated that the electron transfer kinetics of Hb were promoted due to the synergetic effect of GO, AuNPs and MWCNTs. The Hb modified electrode showed good electrocatalytic ability toward the reduction of nitrite. Under optimal conditions, the biosensor could be used for the determination of nitrite with a linear range from 5.0 to 1700 μM and a detection limit of 0.2 μM (S/N = 3). So the proposed method had promising application in constructing direct electrochemistry-based biosensors.