Near-infrared fluorescence probe: BSA-protected gold nanoclusters for the detection of metronidazole and related nitroimidazole derivatives

Abstract

In this work, a novel near-infrared fluorescence probe based on BSA-protected gold nanoclusters (AuNCs@BSA) is designed for the detection of metronidazole (MTZ) and nitroimidazole derivatives. Compared with other wavelengths for fluorescence probes, near-infrared light for MTZ detection has many advantages including effective tissue depth penetration, imaging sensitivity and non-invasivity, and good signal to background noise ratio. The water soluble AuNCs@BSA reported are synthesized through a simple stirring method using BSA and aqueous HAuCl₄ as sources, and there is no further sophisticated modification before the detection. The effects of a series of ions (anions and cations), glucose, amino acids and MTZ on the fluorescence intensity of the prepared AuNCs@BSA are studied, and only the MTZ quenches the fluorescence significantly. The mechanism – that electrons transfer from the NCs to the nitro group of MTZ – has been provided, which means that this probe has the potential to determine other nitroimidazole derivatives, including dimetridazole, ronidazole, tinidazole and ornidazole. For MTZ detection, it has a much lower detection limit of 0.01 μM and a wider range between 0.1 to 10 000 μM than other fluorescence probes. Furthermore, a real sample test in human saliva has been successfully performed.