A Convenient and Label-Free Colorimetric Detection for L-Histidine Based on Inhibition of Oxidation of 3,3',5,5'-Tetramethylbenzidine-H2O2 System Triggered by Copper Ions

Zhikun Zhang; Wenmeng Zhao; Cuixia Hu; Yapeng Cao; Yumin Liu; Qingju Liu

doi:10.3389/fchem.2021.773519

A Convenient and Label-Free Colorimetric Detection for L-Histidine Based on Inhibition of Oxidation of 3,3',5,5'-Tetramethylbenzidine-H₂O₂ System Triggered by Copper Ions

Front Chem. 2021 Nov 23:9:773519. doi: 10.3389/fchem.2021.773519. eCollection 2021.

Authors

Zhikun Zhang¹, Wenmeng Zhao¹, Cuixia Hu¹, Yapeng Cao¹, Yumin Liu¹, Qingju Liu²

Affiliations

¹ School of Chemical and Pharmaceutical Engineering, Hebei University of Science and Technology, Shijiazhuang, China.
² Beijing Research Center for Agriculture Standards and Testing, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China.

Abstract

L-Histidine (L-His) is an essential amino acid, which is used to synthesize proteins and enzymes. The concentration of L-His in the body is controlled to regulate tissue growth and repair of tissues. In this study, a rapid and sensitive method was developed for colorimetric L-his detection using Cu²⁺ ions to inhibit the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB)-H₂O₂ system. H₂O₂ can oxidize TMB to oxTMB in the presence of copper, and the change in color from colorless (TMB) to blue (oxTMB) is similar to that observed in the presence of peroxidase. However, because the imidazole ring and carboxyl group of L-His can coordinate with Cu²⁺ ions to form stable L-His-Cu²⁺ complexes, the color of the TMB-H₂O₂ solution remains unchanged after the addition of L-His. Therefore, because L-His effectively hinders the colorimetric reaction of TMB with H₂O₂, this assay can be used to quantitatively determine the concentration of L-His in samples. Under optimized conditions, our colorimetric sensor exhibited two linear ranges of 60 nM to 1 μM and 1 μM to 1 mM for L-His detection and a detection limit of 50 nM (S/N = 3); furthermore, the assay can be performed within 20 min. Moreover, the proposed assay was used to determine the concentration of L-His in urine samples, suggesting that this convenient and label-free colorimetric method presents promising applications in bioanalytical chemistry and clinical diagnosis.

Keywords: L-histidine; artificial enzyme; colorimetric detection; copper; hydrogen peroxide.