Direct electrochemistry and electrocatalysis of hemoglobin immobilized in layered double hydroxides modified with amino functionalized ionic liquid through coprecipitation technique

Abstract

As the basic modified materials, both of amino functionalized ionic liquid (AFIL) and layered double hydroxides (LDH) can also used to modify bioelectrode and enhance their performance. So AFIL–LDH could be considered as an excellent platform for the immobilization of protein via coprecipitation method and the proposed bioelectrode had potential applications in the fabrication of third-generation biosensors. Hemoglobin (Hb) was firstly immobilized into Zn2Al-LDH modified with AFIL through coprecipitation technique at pH 9.0 to fabricate the enzyme modified glass carbon electrode (AFIL–LDH-Hbcop/GCE) and study the direct electrochemistry of redox protein. The UV–Vis and FTIR spectroscopy of AFIL–LDH-Hbcop composite film illustrated that Hb maintained its natural structure and kept good stability. X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed that AFIL–LDH-Hbcop film had a featured layered structure and a uniform, roughness and porous morphology with Hb being strongly interlocked. Cyclic voltammetric results of AFIL–LDH-Hbcop/GCE showed a pair of well-defined redox peaks appearing with redox peak potentials as −0.285V (Epa) and −0.371V (Epc) in PBS (pH 7.0) at the scan rate of 0.1V/s, indicating the direct electron transfer of Hb-FeIII/FeII. For the synergistic effects of AFIL and LDH, the presence of AFIL–LDHcop composite accelerated the electron transfer rate between GCE and the electroactive center of Hb. The modified bioelectrode displayed good electrocatalytic activity toward the reduction of trichloroacetic acid in the concentration range from 0.8 to 430mmol/L with detection limit as 0.194mmol/L (3σ) by differential pulse voltammetry. The real samples were determined by the modified electrode with satisfactory results.