Highly selective phosphorescent nanoprobes for sensing and bioimaging of homocysteine and cysteine

Most of reported fluorescent probes for mercapto amino acids are organic dyes. They often exhibit poor water-solubility and require the use of biologically toxic organic solvents in sensing and bioimaging. In the present study, a biocompatible phosphorescent nanoprobe by using mesoporous silica nanoparticles as carriers and an iridium(III) complex as signaling units was demonstrated. The nanoprobe exhibits a naked-eye double-signal response for the detection of homocysteine (Hcy) and cysteine (Cys) in pure phosphate buffer saline (PBS), which provides the advantage in effectively avoiding the interference from background signal of biological samples and environmental effects. In addition, the response mechanism, cytotoxicity and bioimaging were studied in detail. These results demonstrated that such a design strategy of phosphorescent nanoprobes is an effective way to develop excellent phosphorescent cellular probes for live cell applications.