Direct electrochemistry and electrocatalysis of horseradish peroxidase on a gold electrode modified with a polystyrene and multiwalled carbon nanotube composite film

We report on the direct electrochemistry and electrocatalysis of horseradish peroxidase immobilized on a composite matrix composed of polystyrene, multiwalled carbon nanotubes and Nafion on a gold electrode. The modified electrode was characterized by scanning electron microscopy, UV-vis and FT-IR spectroscopy. A pair of well-defined redox peak of HRP is obtained with the formal potential at -0.400 V at pH 7.0. The electron transfer rate constant is 1.15 s(-1). The modified electrode exhibits excellent electrocatalytic activity to the reduction of H(2)O(2), with a linear response in the 0.5 mu M to 0.82 mM concentration range and a detection limit at 0.16 mu M (S/N = 3). The apparent Michaelis-Menten constant is 0.66 mM. The modified electrode is biocompatible and conceived to serve as a versatile platform for the fabrication of electrochemical biosensors.