Direct electrochemistry and electrocatalysis of novel single-walled carbon nanotubes-hemoglobin composite microbelts--towards the development of sensitive and mediator-free biosensor.

Single-walled carbon nanotubes (SWNTs) and hemoglobin (Hb) were co-electrospun to generate SWNTs-Hb microbelts, a novel composite material combining the advantages of excellent electron transfer property of SWNTs, electrocatalytic capability of redox Hb proteins, and highly porous structure of microbelts. FT-IR spectra confirmed that Hb in the microbelts kept its native conformational structure and Raman spectra demonstrated the successful incorporation of SWNTs in the microbelts. The direct electrochemistry of SWNTs-Hb composite microbelts was investigated and its application for electrocatalytic reductions and sensitive detections of three compounds, trichloroacetic acid (TCA), nitrite, and hydrogen peroxide (H2O2) was also conducted. The SWNTs-Hb composite microbelts based amperometric biosensor showed fast responses to the analytes with excellent detection limits of 2.41 μM for TCA, 0.30 μM for nitrite, and 0.22 μM for H2O2 (S/N=3), and superior apparent Michaelis-Menten constants of 0.24, 0.491 and 0.070 mM for TCA, nitrite and H2O2, respectively. Its application for spiked tap water was also demonstrated. The comparison of the SWNTs-Hb composite microbelts modified electrode with other reported electrodes in the literature indicates that the incorporation of SWNTs into Hb microbelts can significantly enhance the direct electrochemistry of Hb and the SWNTs-Hb microbelts based biosensor has great potential application in the mediator-free detection of various analytes.