Direct electrochemistry of cytochrome c with three-dimensional nanoarchitectured multicomponent composite electrode and nitrite biosensing

A novel electrochemical nitrite ion (NO2−) biosensor was designed and fabricated by modifying a glassy carbon electrode (GCE) into three-dimensional nanoarchitectured electrode (3DNE) using a multicomponent nanocomposite (MCNC) film composed of graphene embedded titanium dioxide nanowires (TiO2(G) NWs), thiol-functionalized polyaniline (PANI(SH)), gold nanoparticles (Au), and immobilized cytochrome c (cyt c). The new NO2− biosensor was designated as cyt c/TiO2(G) NWs@PANI(SH)-Au MCNC/3DNE. The assembly of the 3DNE, involved sequential depositions of PANI(SH) and Au over previously synthesized TiO2(G) NWs by electrospinning-hydrothermal processes and immobilization of the cyt c onto the TiO2(G) NWs/PANI(SH)/Au MCNC film. The cyt c/TiO2(G) NWs@PANI(SH)-Au MCNC/3DNE exhibited direct electron transfer from cyt c to the electrode at a high rate constant (25.34 s−1). The fabricated cyt c/TiO2(G) NWs@PANI(SH)-Au MCNC/3DNE showed high selectivity to NO2− ions with excellent sensitivity (9.2 μA/mM), a wide linear concentration range (10 μM-720 mM), and a low detection limit (0.05 μM). Additionally, the cyt c/TiO2(G) NWs@PANI(SH)-Au MCNC/3DNE exhibited high stability with good reproducibility and repeatability.