Immobilization of glucose oxidase into a nanoporous TiO2 film layered on metallophthalocyanine modified vertically-aligned carbon nanotubes for efficient direct electron transfer

Glucose oxidase (GOD) was adsorbed into a nanoporous TiO2 film layered on the surface of an iron phthalocyanine (FePc) vertically-aligned carbon nanotube (CNT) modified electrode. A Nafion film was then dropcast on the electrode's surface to improve operational and storage stabilities of the GOD-based electrode. Scanning electron microscopy (SEM) micrographs revealed the formation of FePc and nanoporous TiO2 nanoparticles along the sidewall and the tip of CNTs. Cyclic voltammograms of the GOD electrode in neutral PBS exhibited a pair of well-defined redox peaks, attesting the direct electron transfer of GOD (FAD/FADH2) with the underlying electrode. The potential of glucose electro-oxidation under nitrogen was ∼+0.12 V with an oxidation current density of 65.3 μA cm−2 at +0.77 V. Voltammetric and amperometric responses were virtually unaffected by oxygen, illustrating an efficient and fast direct electron transfer. The modification of the CNT surface with FePc resulted in a biosensor with remarkable detection sensitivity with an oxygen-independent bioelectrocatalysis. In deaerated PBS, the biosensor displayed average response time of 12 s, linearity from 50 μM to 4 mM, and a detection limit of 30 μM (S/N=3) for glucose.

► Glucose oxidase (GOD) was adsorbed into a nanoporous TiO2 film. ► The TiO2 film was layered on iron phthalocyanine (FePc) vertically-aligned carbon nanotubes. ► The GOD electrode in neutral PBS exhibited a pair of well-defined redox peaks. ► FePc nanoparticles contributed to high enzyme loading and bioelectrocatalysis for glucose. ► Voltammetric and amperometric responses of the GOD electrode to glucose were unaffected by O2.