A highly selective ratio fluorescence probe for detecting cysteine and its bioimaging application

Cysteine is an important thiol amino acid that is abundantly present in cells and has an important function in various life processes of the human body. Therefore, it is of great significance to develop an accurate method for monitoring cysteine concentration in cells. We designed and synthesized a novel FRET-ICT-based ratiometric fluorescence and colorimetric probe (BD-C) for detecting cysteine. As cysteine was gradually added, the fluorescence intensity of probe BD-C in buffer solution decreased at 614 nm and increased at 428 nm. The logarithm of the fluorescence intensity ratio to cysteine exhibited favorable linearity in the concentration range of 0.5-14.0 & mu;M, with a detection limit of 395 nM. The energy transfer efficiency of this FRET system is up to 98.8%. BD-C demonstrated preeminent selectivity for cysteine and could specifically react with cysteine, though other sulfhydryl amino acids, such as GSH and Hcy, were present. Furthermore, BD-C exhibited outstanding targeting ability to the endoplasmic reticulum (ER) and was successfully applied in cellular imaging.