Application of an ionic liquid-functionalized Mg2Al layered double hydroxide for the electrochemical myoglobin biosensor

In this paper, an ionic liquid 1-carboxyl-methyl-3-methylimidazolium tetrafluoroborate (CMMIMBF4)-functionalized Mg2Al layered double hydroxide (LDH) was synthesized and further used for the immobilization of myoglobin (Mb) on the surface of a carbon ionic liquid electrode to get a new electrochemical biosensor. Ultraviolet–visible and Fourier transform–infrared spectroscopies confirmed that Mb in the CMMIMBF4-LDH remained its native secondary structure, which was attributed to the biocompatibility of the materials used. On the cyclic voltammograms, a pair of well-defined redox peaks appeared, indicating that direct electron transfer of Mb was realized in the modified electrode. The formal peak potential was calculated as −0.209 V (vs. SCE), which was the typical characteristics of the Mb heme Fe(III)/Fe(II) redox couples. The fabricated Mb sensor exhibited good electrocatalytic activity to the reduction of trichloroacetic acid in the range from 1.0 to 17.0 mmol L−1 with the detection limit as 0.344 mmol L−1 (3σ), and the apparent Michaelis–Menten constant was calculated as 13.5 mmol L−1. Thus, the ionic liquid-functionalized LDH exhibited the potential application in the electrochemical sensor for redox proteins.