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)2C12H25Br2, C12–C12–C12)–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 (O2), 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 μM, and the detection limit is down to 6.5 × 10−8 M. The response shows Michaelis–Menten feature and the apparent Michaelis–Menten constant is estimated to be 110.5 μM. 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 HRP. UV–vis spectrum indicates that the structure of HRP in the PVA–C12–C12–C12 film is similar to that of native HRP. Thus the C12–C12–C12–PVA composite possesses good biocompatibility and has promising application in fabricating biosensor and bioelectronics.