Horseradish Peroxidase Immobilization on Amine Functionalized Carbon Nano Tubes: Direct Electrochemistry and Bioelectrocatalysis

Horseradish peroxidase (HRP) was successfully immobilized on amine functionalized TiO₂-coated multiwalled carbon nanotubes (NH₂ TiO₂ CNTs) by a convenient and efficient method. Electrochemical impedance spectroscopy, cyclic voltammetry and amperometry were applied to characterize the HRP/NH₂- TiO₂ - CNT nano-composite. These techniques showed that the NH₂ TiO₂CNTs greatly enhance the electron transfer between HRP and the modified electrode. Owing to the redox reaction of the electroactive centre of HRP, the HRP/NH2-TiO₂-CNTs modified electrode exhibited a pair of quasi-reversible peaks with a peak-to-peak separation (Δ E_p) of 70.6 m V and a formal potential (E°’) of - 367.65 m V (versus Ag/AgCl) in phosphate buffer solution. The charge transfer coefficient (a) and the apparent charge transfer rate constant (k_s) were found to be 0.34 and 2.08 s-1 respectively. The prepared biosensor responded to H₂O₂ with a linear range, detection limit, sensitivity and response time of 1.0 × 10⁻⁹ to 1.0 × 10 ⁻⁷ M, 0.786nM, 28.4 μA A nM⁻¹ and 3 s, respectively.