Phosphorescent Inner Filter Effect-based Sensing System for Determination of β-glucuronidase Using Manganese-doped Zinc Sulfide Quantum Dots

The key to maximize the sensitivity of inner filter effect (IFE)-based assay is to enlarge the overlap between the absorption spectra of the absorber and the excitation and/or emission bands of the fluorophore. In this work, Mn-doped ZnS QDs is chosen for IFE-based detection of β -glucuronidase (GUS), since the excitation spectrum of QDs is perfectly overlapped with the absorption spectrum of the substrate of GUS, namely 4-nitrophenyl- β-D- glucuronide (PNPG). Since absorption spectrum of the enzymatic product of GUS-PNP are almost not overlapped with the excitation and emission spectra of Mn-ZnS QDs, the phosphorescent turn-on determination of GUS can be successfully proposed and carried out. In addition, the excellent room temperature phosphorescence property of Mn-ZnS QDs can eliminate the fluorescence background from biological organisms, which can be effectively applied to biological sample analysis with good anti-interference ability. Accordingly, a simple turn-on phosphorescent assay of GUS was developed with a linear range of 10–300 U L −1 and a limit of detection of 7 U L −1 , and the proposed system was also successfully applied for actual detection of Escherichia coli .