A sensitive ratiometric fluorescent probe for quantitive detection and imaging of alkaline phosphatase in living cells.

We report a sensitive fluorescence probe Ratio-ALP for in vivo ratiometric imaging of alkaline phosphatase (ALP). The probe was designed by conjugating a naphthalimide with a phosphate group as the responsive moiety for enzymatic reactions. The fluorescence intensity ratio displayed a linear relationship against the concentration of ALP in the concentration range from 0 to 200 U/L, its LOD is as low as 0.25 U/L. Ratio-ALP has good selectivity and sensitivity, high cell permeability, and low cytotoxicity. Furthermore, probe Ratio-ALP was also successfully applied to image endogenous ALP activity in living cells.

Dual-Site Fluorescent Probe to Monitor Intracellular Nitroxyl and GSH-GSSG Oscillations.

Nitroxyl (HNO), the one-electron-reduction product of NO has recently been revealed to have potentially beneficial pharmacological properties in cardiovascular health as a result of interactions with specific thiols such as glutathione (GSH). To disentangle the complicated inter-relationship between HNO and GSH in the signal transduction and oxidative pathways, we designed and synthesized a dual-site fluorescent probe NCF to indicate cellular HNO and GSH-GSSG balance. The sensitive and selective detection of HNO was achieved by incorporating an organophosphine group to naphthaldehyde-TCF. Then the resulted fluorescent product is able to monitor the conversion of GSH and GSSG reversibly. Additionally, outstanding biocompatibility make it capable of monitoring intracellular HNO and consequently GSH-GSSG oscillationsin living cells. We anticipate that NCF will be a unique molecular tool to investigate the interplaying roles of HNO and GSH.

A lysosome targetable versatile fluorescent probe for imaging viscosity and peroxynitrite with different fluorescence signals in living cells.

The lysosome, which acts as the cellular recycling centre, is filled with numerous hydrolases that can degrade most cellular macromolecules. The abnormalities of the lysosome are closely associated with diseases, such as Hermanský-Pudlák syndrome, Griscelli syndrome and Chédiak-Higashi syndrome. Studies have shown that abnormal viscosity and the accumulation of reactive oxygen species (ROS) in the lysosome will disorder the normal function of the lysosome. In this research, a versatile fluorescent probe Lyso-NA has been developed for the multi-channel imaging of lysosomal viscosity and peroxynitrite (ONOO-). When excited at 550 nm, the Lyso-NA exhibited about a 50-fold increase in fluorescence at 610 nm and also with the increasing viscosity from 1.0 cP to 1410 cP, and about a 3.5-fold increase in fluorescence at 510 nm (excitation at 440 nm) together with the increasing ONOO-. These satisfactory response properties make it possible to use Lyso-NA to monitor changes in both viscosity and ONOO- inside the lysosome. To achieve its practical application, it was further demonstrated that Lyso-NA exhibits low cytotoxicity, and good cell permeability, and could be used to monitor lysosomal viscosity and ONOO- in living cells.

Specific and sensitive imaging of basal cysteine over homocysteine in living cells.

Biological thiols play important roles in maintaining appropriate redox status of organisms. Accepting the challenge to differentiate structurally similar cysteine (Cys) and homocysteine (Hcy), we have successfully developed a miniature synthetic turn-on fluorescent probe based on 6-(2-benzothiazolyl)-2-naphthalenol for Cys. This probe is able to specifically react with Cys to yield its naphthalenol derivative, accompanied by remarkable green fluorescence enhancement with a detection limit of 14.8 nM. Besides, this probe displays much greater selectivity for Cys over other biological thiols, including homocysteine (Hcy) and glutathione (GSH). Practically, good cell permeability and low cytotoxicity make it suitable for monitoring basal Cys in living cells.