Development and Application of an Efficient Medium for Chromogenic Catalysis of Tetramethylbenzidine with Horseradish Peroxidase

The alkylimidazolium tetrafluoroborate ionic liquids (ILs) ([Cnmim][BF4] n = 2, 4, 6, 8, 10) and anionic surfactant sodium dodecyl sulfate (SDS) were combined together to produce effective mediums for chromogenic catalysis of tetramethylbenzidine (TMB) with horseradish peroxidase (HRP) in the presence of H2O2. The chromogenic performance, kinetic behavior, and the possible influencing mechanism for the chromogenic catalysis of HRP-H2O2-TMB were discussed in detail. Therein, the roles of ionic liquids (ILs) were highlighted by the combination of experiments and theoretical calculations. The SDS/[C4mim][BF4] combination displayed superiority in chromogenic catalysis by improving both the substrate solubility and product stability to the maximum extent possible. Furthermore, SDS/[C4mim][BF4] combination showed uniqueness for TMB in improving the chromogenic performance compared with other chromogenic substrates of HRP. Inspired by the efficient chromogenic system, an enhanced enzyme-linked immunosorbent assay strategy for the detection of human immunoglobulin G was established and the sensitive colorimetric strategies for the detection of H2O2 and glucose were further developed by employing SDS/[C4mim][BF4] combination as the medium of chromogenic catalysis of HRP-H2O2-TMB. This unique chromogenic system is endowed with multitude of potential applications in biological systems.