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.