Electrochemical performance of myoglobin based on TiO2-doped carbon nanofiber decorated electrode and its applications in biosensing

Abstract

A new biosensing strategy based on a TiO₂-doped carbon nanofiber (CNF) composite modified electrode was developed. TiO₂@CNF was prepared by electrospinning with further carbonization, before being characterized by various methods and used for electrode modification on the surface of carbon ionic liquid electrode (CILE). Myoglobin (Mb) was further immobilized on the modified electrode surface. The results of ultraviolet-visible (UV-vis) and Fourier transform infrared (FT-IR) spectroscopy showed that Mb maintained its native structure without denaturation in the composite film. Direct electron transfer and the electrocatalytic properties of Mb on the electrode surface were further investigated. A pair of quasi-reversible redox peaks appeared on the cyclic voltammogram, indicating that direct electrochemistry of Mb was realized in the nanocomposite film. This could be attributed to the specific properties of TiO₂@CNF nanocomposite, including a large surface-to-volume ratio, good biocompatibility and high conductivity. Nafion/Mb/TiO₂@CNF/CILE exhibited an excellent electrochemical catalytic ability in the reduction of trichloroacetic acid, NaNO₂ and H₂O₂. All results demonstrated potential applications of TiO₂@CNF in third-generation electrochemical biosensors.

Fig. 1. Characterization of TiO₂@CNF nanocomposite: (A and B) SEM images; (C–E) TEM images; (F) XRD pattern; (G and H) XPS spectra and (I) Raman spectra.

Fig. 2. Cyclic voltammograms of Nafion/CILE (curve a), Nafion/TiO₂@CNF/CILE (curve b), Nafion/Mb/CILE (curve c) and Nafion/Mb/TiO₂@CNF/CILE (curve d) in pH 4.0 PBS with a scan rate of 100 mV s⁻¹.

Fig. 3. (A) Cyclic voltammograms of Nafion/Mb/TiO₂@CNF/CILE at different pH (curves a → f: 3.0, 4.0, 5.0, 6.0, 7.0, 8.0) with a scan rate of 100 mV s⁻¹. (B) Cyclic voltammograms of Nafion/Mb/TiO₂@CNF/CILE at different scan rates (curves a → k: 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 mV s⁻¹) in pH 4.0 PBS.

Fig. 4. Cyclic voltammograms of Nafion/Mb/TiO₂@CNF/CILE in pH 4.0 PBS in the presence of (A) 0, 3, 6, 10, 15, 20, 26, 32, 38, 44, 50, 60, 70, 80, 90, 105 mmol L⁻¹ TCA (curves a to p, inset is the linear relationship of catalytic reduction peak currents vs. TCA concentration); (B) 0, 6, 9, 12, 20, 30, 40, 50, 60, 70 mmol L⁻¹ NaNO₂ (curves a to j, inset is the linear relationship of catalytic reduction peak currents vs. NaNO₂ concentration); (C) 0, 1, 2, 3, 5, 7, 10, 15, 20, 25, 30, 32 mmol L⁻¹ H₂O₂ (curves a to l, inset is the linear relationship of the catalytic reduction peak currents vs. H₂O₂ concentration).