Fe(III) bipyridyl or phenanthroline complexes with oxidase-like activity for sensitive colorimetric detection of glutathione

One-pot synthesized copper-imidazole-2-carboxaldehyde complex material with oxidase-like activity for the colorimetric detection of glutathione and ascorbic acid

Due to the copper (Cu) active sites, its complexes with oxidase-like activity have superior catalytic properties, which can catalyze a series of specific substrates like 3,3',5,5'-tetramethylbenzidine (TMB), producing colorimetric reactions for the detection of different reducing small-molecule compounds. Attribute to the competitive coordination effects between water molecules and central Cu ions, most of the Cu complexes can hardly be used in the pure aqueous reaction system. In this study, a Cu-based material (Cu-imidazole-2-carboxaldehyde, Cu-ICA) was prepared using copper ions and ICA through a one-step process in the water solution. After the morphology of the material being characterized, the mimetic enzyme behavior of the Cu-ICA was demonstrated through the TMB oxidation. Compared to the other reported oxidase-like mimics, Cu-ICA has better aqueous stability and oxidase-like activity, and shows a higher vmax. Furthermore, basing on the oxidase-like activity of Cu-ICA, a colorimetric method was developed for the ascorbic acid and glutathione detections with linear ranges of 0.5-5 μM and 0.5-4 μM, and limit of detection of 0.1304 μM and 0.097 μM, respectively. Owing to its excellent aqueous stability and oxidase-like activity, Cu-ICA has bright application prospects in the analysis of reducing small-molecule compounds.

Colorimetric Systems for the Detection of Bacterial Contamination: Strategy and Applications

Bacterial contamination is a public health concern worldwide causing enormous social and economic losses. For early diagnosis and adequate management to prevent or treat pathogen-related illnesses, extensive effort has been put into the development of pathogenic bacterial detection systems. Colorimetric sensing systems have attracted increasing attention due to their simple and single-site operation, rapid signal readout with the naked eye, ability to operate without external instruments, portability, compact design, and low cost. In this article, recent trends and advances in colorimetric systems for the detection and monitoring of bacterial contamination are reviewed. This article focuses on pathogen detection strategies and technologies based on reaction factors that affect the color change for visual readout. Reactions used in each strategy are introduced by dividing them into the following five categories: external pH change-induced pH indicator reactions, intracellular enzyme-catalyzed chromogenic reactions, enzyme-like nanoparticle (NP)-catalyzed substrate reactions, NP aggregation-based reactions, and NP accumulation-based reactions. Some recently developed colorimetric systems are introduced, and their challenges and strategies to improve the sensing performance are discussed.