An electrochemical biosensor based on Nafion-ionic liquid and a myoglobin-modified carbon paste electrode

An electrochemical biosensor was constructed based on the immobilization of myoglobin (Mb) in a composite film of Nafion and hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) for a modified carbon paste electrode (CPE). Direct electrochemistry of Mb in the Nafion–BMIMPF6/CPE was achieved, confirmed by the appearance of a pair of well-defined redox peaks. The results indicate that Nafion–BMIMPF6 composite film provided a suitable microenvironment to realize direct electron transfer between Mb and the electrode. The cathodic and anodic peak potentials were located at −0.351 V and −0.263 V (vs. SCE), with the apparent formal potential (Ep) of −0.307 V, which was characteristic of Mb Fe(III)/Fe(II) redox couples. The electrochemical behavior of Mb in the composite film was a surface-controlled quasi-reversible electrode process with one electron transfer and one proton transportation when the scan rate was smaller than 200 mV/s. Mb-modified electrode showed excellent electrocatalytic activity towards the reduction of trichloroacetic acid (TCA) in a linear concentration range from 2.0 × 10−4 mol/L to 1.1 × 10−2 mol/L and with a detection limit of 1.6 × 10−5 mol/L (3σ). The proposed method would be valuable for the construction of a third-generation biosensor with cheap reagents and a simple procedure.