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 HgZnSe 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. Cu2+ could be selectively enriched on the surface of ZIF-8@QDs, and resulting in its fluorescence quenching. However, in the presence of glutathione (GSH), ZIF8@QDs fluorescence was recovered due to the strong affinity between Cu2+ 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 Cu2+, leading to ZIF-8@QDs fluorescence quenched again. Hence, a simple and sensitive off-onoff 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.

Automated summary

In this study, a highly sensitive method for the determination of glutathione S-transferase (GST) was developed using a fluorescent nanosensor. The nanosensor, based on the assembly of HgZnSe quantum dots (QDs) and zeolitic imidazolate framework-8 (ZIF-8), exhibited enhanced fluorescence and improved analytical sensitivity. The platform relied on the selective enrichment of Cu2+ on the surface of ZIF-8@QDs, resulting in fluorescence quenching. However, the presence of glutathione (GSH) led to the recovery of fluorescence due to the strong affinity between Cu2+ and GSH. The catalysis of GST caused GSH to react with 1-chloro-2,4-dinitrobenzene (CDNB), resulting in the formation of an adduct that quenched the fluorescence of ZIF-8@QDs. This simple and sensitive fluorescence sensing platform showed a wide linear range of 0.05-1.2 mU/L for the determination of GST, with a limit of detection (LOD) of 0.014 mU/L. The study highlights the potential of designing and synthesizing high-performance MOF-based nanoprobes for in vitro diagnosis, with applications in bioinformatics and clinical medicine.