Gold Nanocluster-Based Ratiometric Probe with Surface Structure Regulation-Triggered Sensing of Hydrogen Sulfide in Living Organisms

The development of reliable probes for in vivo detection of hydrogen sulfide (H 2 S) with high sensitivity and selectivity is of great significance due to its key roles in many pathological and physiological processes. Herein, it was found that H 2 S could finely regulate surface structure of gold nanoclusters (AuNCs) through reduction of surface Au(I)-ligand motifs and further quench their fluorescence by a two-stage kinetic reaction process. Stage I showed the H 2 S-assisted surface Au(I)-ligand reduction and Au(0) core growth with a rapid fluorescence decrease; stage II showed the surface structure optimization and reconstruction with a relatively slow fluorescence quenching. By virtue of the excellent fluorescence response of AuNCs to H 2 S, a novel ratiometric fluorescence probe (RBDA) for sensing H 2 S was designed through electrostatic attraction-induced fluorescence resonance energy transfer (FRET) between AuNCs and rhodamine B. The probe was facilely prepared, showing a straightforward, rapid ratiometric fluorescence response to H 2 S with built-in self-calibration. It presented the high detection sensitivity with a detection limit (LOD) of 56 nM and an excellent sensing selectivity for H 2 S over various other biological species. The probe was demonstrated to possess high biostability, low cytotoxicity, good cell and issue penetrability, and favorable biocompatibility. It realizes successful monitoring of both exogenous and endogenous H 2 S levels in living cells and zebrafish.