Direct electrochemistry and electrocatalysis of hybrid film assembled by polyelectrolyte–surfactant polymer, carbon nanotubes and hemoglobin

Functional hybrid film based on the incorporation of multiwalled carbon nanotubes modified with hemoglobin into polyelectrolyte–surfactant polymer was fabricated. Such assembled films are found to possess facilitated electron transfer of hemoglobin. Cyclic voltammetric results showed a pair of well-defined redox peaks for the Hb heme Fe(III)/Fe(II) redox couple at about −0.273 (versus SCE) in a pH 7.0 phosphate buffer solution. The formal potential of the Hb heme Fe(III)/Fe(II) couple shifted linearly with pH with a slope of 52.8 mV pH−1, indicating that an electron transfer is coupled with a one-proton transportation. An FT-IR and UV–vis spectroscopy study confirms that the secondary structure of Hb entrapped in the hybrid film still maintains the original arrangement. It is suggested that the achieved faradic response of the hemoglobin be due to the ability of carbon nanotubes to promote the electron transfer of enzymes and the biomembrane properties of the polyelectrolyte–surfactant polymer. And the entrapped Hb exhibits the features of a peroxidase and acts in an electrocatalytic manner in the reduction of hydrogen peroxide, oxygen, and nitrite. The properties of the functional hybrid films, combined with the bioelectrochemical catalytic activity, could make them useful for the development of bioelectronic devices and investigation of protein electrochemistry at functional interface.