In the present study, a glucose oxidase (GluOx) direct electron transfer was realized on an aminated polyethylene glycol (mPEG), carboxylic acid functionalized multi-walled carbon nanotubes (fMWCNTs), and ionic liquid (IL) composite functional polymer modified glassy carbon electrode (GCE). The amino groups in PEG, carboxyl groups in multi-walled carbon nanotubes, and IL may have a better synergistic effect, thus more effectively adjust the hydrophobicity, stability, conductivity, and biocompatibility of the composite functional polymer film. The composite polymer membranes were characterized by cyclic voltammetry (CV), ultraviolet-visible (UV-Vis) spectrophotometer, fluorescence spectroscopy, electrochemical impedance spectroscopy (EIS), and transmission electron microscopy (TEM), respectively. In 50 mM, pH 7.0 phosphate buffer solution, the formal potential and heterogeneous electron transfer constant (ks) of GluOx on the composite functional polymer modified GCE were −0.27 V and 6.5 s−1, respectively. The modified electrode could recognize and detect glucose linearly in the range of 20 to 950 μM with a detection limit of 0.2 μM. The apparent Michaelis-Menten constant (Kmapp) of the modified electrode was 143 μM. The IL/mPEG-fMWCNTs functional polymer could preserve the conformational structure and catalytic activity of GluOx and lead to high sensitivity, stability, and selectivity of the biosensors for glucose recognition and detection.

The conformational lock was a bio-thermodynamic theory to explain the characteristics of interfaces in oligomeric enzymes and their effects on catalytic activity. The previous studies on superoxide dismutases (Cu, Zn-SODs) showed that the dimeric structure contributed to the high catalytic efficiency and the stability. In this study, steered molecular dynamics simulations were used firstly to study the main interactions between two subunits of Cu, Zn-SODs. The decomposition process study showed that there were not only four pairs of hydrogen bonds but also twenty-five residue pairs participating hydrophobic interactions between A and B chains of SOD, and van der Waals interactions occupied a dominant position among these residue pairs. Moreover, the residue pairs of hydrogen bonds played a major role in maintaining the protein conformation. The analysis of the energy and conformational changes in the SMD simulation showed that there were two groups (two conformational locks) between A and B chains of SOD. The first group consisted of one hydrogen-bond residues pair and seven hydrophobic interactions residues pairs with a total average energy of −30.10 KJ/mol, and the second group of three hydrogen-bond residues pair and eighteen hydrophobic interactions residues pairs formed with a total average energy of −115.23 KJ/mol.

By immobilizing catalase on a functional nanocomposites containing ion-liquid, TiO2 nano particles and carboxylic acid functionalized multi-walled carbon nanotubes, direct electron transfer of CAT was realized on the nanocomposites modified glassy carbon electrode. The electrochemical study showed that the formal potential and heterogeneous electron transfer constant of the prepared modified glassy carbon electrode were −0.163 V and 5.24 s −1 , respectively. The electrocatalysis study showed that the linear response range toward H2O2 and the apparent Michaelis-Menten constant were from 5 µM to 1000 µM and 54.3 µM, respectively.