Fabrication of red-emissive ZIF-8@QDs nanoprobe with improved fluorescence based on assembly strategy for enhanced biosensing

In this study, brightly red-emissive nanoprobe (ZIF-8@QDs) was constructed based on the assembly between Hg-ZnSe QDs and zeolitic imidazolate framework-8 (ZIF-8) for ultrasensitive determination of glutathione S-transferase (GST). The ZIF-8@QDs nanoprobe not only enhanced the fluorescence of QDs, but also had the advantages of MOFs, which largely improved the analytical sensitivity. Cu 2+ could be selectively enriched on the surface of ZIF-8@QDs, and resulting in its fluorescence quenching. However, in the presence of glutathione (GSH), ZIF-8@QDs fluorescence was recovered due to the strong affinity between Cu 2+ and GSH. Moreover, with the catalysis of GST, GSH would react with 1-chloro-2,4-dinitrobenzene (CDNB) to form an adduct that could not coordinate with Cu 2+ , leading to ZIF-8@QDs fluorescence quenched again. Hence, a simple and sensitive "off-on-off" fluorescent sensing platform was fabricated for the determination of GST with a wide linear range of 0.05–1.2 mU/L. Moreover, the LOD of the ZIF-8@QDs nanoprobe for GST was 0.014 mU/L, which was improved about 15 times compared with QDs nanoprobe. This assay provided a promising method to design and synthesize high-performance MOF-based nanoprobe for in vitro diagnosis and possessed great potential in the field of bioinformatics and clinical medicine. Schematic diagram of the preparation of ZIF-8@QDs nanoprobe and its detection principle for GST activity. • The red-emissive ZIF-8@QDs nanoprobe was prepared based on assembly strategy. • The combination of QDs and ZIF-8 prevented QDs aggregation and improved QDs fluorescence. • The ZIF-8@QDs nanoprobe had the advantages of MOFs that can selectively accumulate analytes. • The improved fluorescence and accumulation effect of ZIF-8@QDs amplified the sensing signal. • The ZIF-8@QDs nanoprobe achieved multiple targets detection with enhanced sensitivity.