Protein-directed synthesis of fluorescent sulfur quantum dots for highly robust detection of pyrophosphate

Inorganic pyrophosphate anions (PPi) play a key role in various biological processes and act as an essential indicator for physiological function evaluation and disease diagnosis. However, there is still a lack of available approaches for straightforward, robust, and convenient PPi detection. Herein, we design an on-off-on fluorescent switching nanoprobe employing Fe3+-mediated fluorescent sulfur quantum dots (SQDs) for highly robust detection of PPi. The bovine serum protein (BSA)-capped SQDs with fine water dispersibility and good optical stability are synthesized by an H2O2-assisted chemical etching reaction. Specifically, Fe3+ can strongly induce the aggregation of the SQDs into relatively larger sizes, resulting in aggregation-induced fluorescence quenching behavior. PPi can selectively bind with Fe3+ via emulative coordination and in preventing the aggregation of SQDs this is accompanied by recovery of fluorescence. The physicochemical properties of aggregated and disaggregated SQDs have been systematically investigated. Aggregation and disaggregation of the SQDs and the corresponding quenching and recovery of fluorescence occurs and guarantees the high-contrast sensing performance of the SQD system in complex and challenging aquatic environments. Our designed on-off-on nanoswitch holds great potential for the design of elemental quantum dot-based biosensors for the highly robust detection of analytes in the near future.

Automated summary

Inorganic pyrophosphate anions (PPi) play a crucial role in biological processes and serve as important indicators for physiological function evaluation and disease diagnosis. However, there is a lack of straightforward and robust approaches for PPi detection. In this study, an on-off-on fluorescent switching nanoprobe utilizing Fe3+-mediated fluorescent sulfur quantum dots (SQDs) is designed for highly robust PPi detection. The SQDs, capped with bovine serum protein (BSA), exhibit good water dispersibility and optical stability. The presence of Fe3+ induces aggregation of the SQDs, leading to fluorescence quenching. PPi selectively binds with Fe3+, preventing SQD aggregation and resulting in fluorescence recovery. The designed nanoswitch shows great potential for the future development of quantum dot-based biosensors for analyte detection.