Improved direct electron transfer and electrocatalytic activity of horseradish peroxidase immobilized on gemini surfactant-polyvinyl alcohol composite film

The voltammetric and electrocatalytic behavior of horseradish peroxidase (HRP) immobilized on a cationic gemini surfactant (i.e. C12H25N(CH3)(2)-C12H24-N(CH3)(2)C12H25Br2, C-12-C-12-C-12)-polyvinyl alcohol (PVA) composite film-coated glassy carbon electrode (GCE) has been studied. It is found that on the novel composite film HRP presents excellent electroactivity and can exhibit a pair of well-defined voltammetric peaks in 0.10 M pH 7.0 phosphate buffer solution (PBS). The immobilized HRP also presents good bioelectrocatalytic activity, and it can catalyze the reduction of oxygen (O-2), hydrogen peroxide (H2O2), nitrite ion (NO2-) and trichloroacetic acid (TCA). For H2O2 the catalytic current is linear to its concentration in the range of 0.195-97.5 mu M, and the detection limit is down to 6.5 x 10(-8) M. The response shows Michaelis-Menten feature and the apparent Michaelis-Menten constant is estimated to be 110.5 mu M. Similarly, the electrode can sense NO2- and TCA. In addition, it is observed that the spacer group of gemini surfactant affects the electroactivity of HRP significantly. A spacer group with higher flexibility and hydrophility is favorable to the electron transfer of HRR UV-vis spectrum indicates that the structure of HRP in the PVA-C-12-C-12-C-12 film is similar to that of native HRP. Thus the C-12-C-12-C-12-PVA composite possesses good biocompatibility and has promising application in fabricating biosensor and bioelectronics. (C) 2008 Elsevier B.V. All rights reserved.