Bioelectrocatalytic and biosensing properties of horseradish peroxidase covalently immobilized on (3-aminopropyl)trimethoxysilane-modified titanate nanotubes

Titanate nanotubes (TiNT) surface modified with (3-aminopropyl)trimethoxysilane were employed as a support for covalent immobilization of horseradish peroxidase (HRP) by using 1,4-benzoquinone as a coupling agent. Composite film-electrodes consisting of HRP-modified TiNT embedded into the porous carbon powder/Nafion matrix were fabricated and their applicability in direct bioelectrocatalytic reduction of H₂O₂ and H₂O₂ biosensing were investigated. An efficient direct electron transfer between the immobilized HRP molecules and the electrode was observed in the presence of H₂O₂ at potentials lower than 600 mV (vs. Hg/Hg₂Cl₂/3.5 M KCl). For the HRP–TiNT-modified electrodes polarized at 0 mV, a linear dependence of the bioelectrocatalytic current on the concentration of H₂O₂ was observed up to the concentration of H₂O₂ equal to 10 μM, with the sensitivity of (1.10 ± 0.01) AM⁻¹ cm⁻² and the detection limit of 35 nM.