A novel ratiometric peptide-based fluorescent probe for sequential detection of Hg and S ions and its application in living cells and zebrafish imaging.

A new ratiometric peptide-based fluorescent probe DWPH was designed and synthesized, comprising dansyl fluorophore as a fluorescent dye, and tripeptide backbone (Trp-Pro-His-NH) as a recognition group. The addition of Hg caused the maximum emission peak of DWPH to blue shift from 560 nm to 510 nm. DWPH exhibited large Stokes shift (230 nm), satisfactory water solubility (100 % aqueous medium), good selectivity (only Hg), high sensitivity (24.6 nM), rapid response (within 50 s) and strong anti-interference ability for Hg detection over a wide pH range (7-11). Additionally, the complex DWPH-Hg as a relay response probe could also be applied to S according to displacement approach. Notably, the detection limit for S was calculated as 23.3 nM, exhibiting that DWPH showed great potential for environmental monitoring and bioimaging. In addition, DWPH were successfully used to determine Hg and S in living cells and zebrafish based on excellent permeability and low cytotoxicity. What's more, the gradient concentration color changes of Hg and S were combined with the smartphone APP to obtain red-green-blue (RGB) values, thus enabling rapid semi-quantitative detection of Hg and S without expensive instruments.