A Förster Resonance Energy Transfer Ratiometric Probe Based on Quantum Dot-Cresyl Violet for Imaging Hydrogen Sulfide in Living Cells
Abstract Hydrogen sulfide (H2S) has been confirmed as a significant endogenous gaseous signaling molecule involved in various physiological processes. In order to monitor H2S in living cells, a Forster resonance energy transfer (FRET) ratiometric probe based on quantum dot-cresyl violet was developed. In this work, the quantum dot nanospheres via a facile ultrasonication emulsion strategy, and the mixture chloroform solution containing hydrophobic quantum dots and COOH-functionalized amphiphilic polymer were successfully transferred into the oil-in-water micelle. The negatively charged quantum dot nanospheres with quantum dots embedded in the polymer matrixes were successfully fabricated after the evaporation of chloroform. And then, these quantum dot nanospheres were condensed with positively charged cresyl violet-azide (CV-N3) via electrostatic interaction to obtain the complexes (QDS-N3). The as-prepared QDS-N3 complexes were monodispersed nanospheres with an average diameter of about 120 nm. These complexes were taken up by the cell through endocytosis, and they were still stable even in wide pH range. In addition, the QDS-N3 complexes exhibited no cellular toxicity which was verified by MTT assay. In this ratiometric probe, CV-N3 as a FRET acceptor was conjugated to quantum dot nanospheres. The quantum dots emitted at 591 nm and served as the FRET donor; once the aryl azide on the CV-N3 was reduced by H2S to aniline, the probe emitted at 620 nm. The ratiometric probe allowed the elimination of interference of excitation intensity, intracellular environment and other factors. Furthermore, this method also offered a general protocol for preparing nanosensors for monitoring various small molecular in living cells.