Structural characterization and electrocatalytic application of hemoglobin immobilized in layered double hydroxides modified with hydroxyl functionalized ionic liquid

Hemoglobin (Hb) was immobilized in Zn2Al-Layered Double Hydroxides (LDH) modified with Hydroxyl Functionalized Ionic Liquid (HFIL) through adsorption and coprecipitation method, respectively. Adsorption experiments showed that the presence of HFIL could enhance the maximum protein loading. However, the Hb loading through coprecipitation technique was far higher than that for adsorption. The role of HFIL on the interaction between Hb and LDH was investigated by XRD, FTIR, UV-vis and fluorescence spectroscopies. Although the quaternary structure of Hb entrapped in HFIL-LDH through coprecipitation technique (denoted as HFIL-LDH-Hb(cop)) might be altered slightly more than that in LDH (LDH-Hb(cop)), its secondary structure and redox-active heme groups kept intact. Morphologies of LDH-Hb(cop) and HFIL-LDH-Hb(cop) biohybrids were analyzed through SEM and TEM images. The direct electrochemistry of the immobilized Hb indicated that the coprecipitation bioelectrode performed better than that of the corresponding adsorption one. Regardless of adsorption and coprecipitation, the introduction of HFIL could distinctly promote the electron transport. Among all bioelectrodes, HFIL-LDH-Hb(cop)/GCE displayed the best electrocatalytic activity for H2O2 determination with a larger electroactive Hb percentage (6.76%), higher sensitivity (40.63 A/M cm(2)) and lower detection limit (0.0054 mu mol/L). So HFIL-LDH could effectively immobilize enzymes via coprecipitation technique, which had potential applications in the fabrication of electrochemical biosensors. (C) 2014 Elsevier Inc. All rights reserved.