Direct Electrochemistry and Electrocatalysis of Myoglobin with Ionic Liquid through Multilayers Film on Carbon Ionic Liquid Electrode

Multilayers of myoglobin (Mb) with ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM]BF4) was assembled on carbon ionic liquid electrode (CILE) based on the electrostatic attraction between the negatively charged Mb and the positively charged imidazolium ion of IL. The CILE was fabricated with 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM]EtOSO3) as the modifier, which exhibited imidazolium ion on the electrode surface. Then Mb molecules were assembled on the surface of CILE step-by-step to get a {IL/Mb}(n), multilayer film modified electrode. UV-Vis adsorption and FT-IR spectra indicated that Mb remained its native structure in the IL matrix. In deaerated phosphate buffer solution (pH 7.0) a pair of well-defined quasi-reversible redox peaks appeared with the apparent formal potential (E-0') as -0.212 V (vs. SCE), which was the characteristic of Mb heme Fe(III)/Fe(H) redox couples. The results indicated that the direct electron transfer of Mb was realized on the modified electrode. The {IL/Mb}(n)/CILE displayed excellent electrocatalytic ability to the trichloroacetic acid reduction in the concentration range from 2.0 to 22.0 mmol/L with the detection limit of 0.6 mmol/L (3 sigma). The proposed method provides a new platform to fabricate the third generation biosensor based on the self-assembly of redox protein with ILs.