Enhancing direct electron transfer of glucose oxidase using a gold nanoparticle |titanate nanotube nanocomposite on a biosensor

In this paper, we have developed a gold nanoparticle (GNP) decorated titanate nanotubes (TNT) nanocomposite that aids in the direct electron transfer of a large enzyme, such as glucose oxidase (GOD), in which the electroactive site of flavin adenine dinucleotide is deeply buried within the enzyme. The ionic liquid, brominated 1-decyl-3-methyl imidazole, was used to immobilise the nanocomposite and the enzyme on a glassy carbon electrode to further aid in the electron transfer between GOD and the electrode surface. Nafion was also added to anchor the biosensor scaffold. Initially, the tubiform geometry of titanate nanomaterials and the GNP-TNT nanocomposite was confirmed by microscopic and spectroscopic techniques before glucose oxidase was entrapped in the nanocomposite. Based on voltammetric results, this biosensor showed a strong electrocatalytic capability towards glucose (with a heterogeneous electron transfer rate constant of 7.1 s^-1 at 180 mV s^-1) and the calibration for glucose exhibited a high sensitivity (5.1 μA mM^-1) and a wide linear range (0.01-1.2 mM). These results demonstrated superior analytical performance of our biosensor over others fabricated using bulkier TiO₂ nanoparticles or nanobundles, which could be attributed to a high degree of biocompatibility to glucose oxidase and electrical conductivity of the nanocomposite.