A fluorescent switch for sequentially and selectively sensing copper(II) and L-histidine in vitro and in living cells

National Natural Science Foundation of China [21175122, 91127036, 21375121]; Fundamental Research Funds for Central Universities [WK2060190018]Herein, we report the development of a new fluorescent switch for sequential and selective sensing of Cu2+ and L-histidine (L-His) in vitro and in living cells for the first time. In the absence of metal ions, Ac-SAACQ- Gly-Gly-Gly-Lys (FITC) (1) exhibits comparable fluorescence to that of free FITC. In the presence of metal ions, 1 selectively coordinates to Cu2+, causing its fluorescence emission to be quenched via photoinduced electron transfer. Interestingly, the as-formed 1-Cu2+ complex selectively responds to L-His among the 20 natural amino acids by turning its fluorescence on. This property of fluorescence switch of 1 was successfully applied for qualitatively and quantitatively sensing Cu2+ and L-His in vitro. Using this dual functional probe, we also sequentially imaged Cu2+ and L-His in living HepG2 cells. Our new probe 1 could be applied for not only environmental monitoring but also biomolecule detection in the near future

Bipyridine hydrogel for selective and visible detection and absorption of Cd2+

Herein, we report for the first time the use of bipyridine-based hydrogel for selective and visible detection and absorption of Cd2+. At low concentrations, hydrogelator 1 was applied for selective detection of Cd2+ in vitro and in living cells with high sensitivity. In the absence of metal ions, 1 is nonfluorescent at 470 nm. Upon addition of metal ions, 1 selectively coordinates to Cd2+, causing an 86-fold increase of fluorescence intensity at 470 nm via the chelation enhanced fluorescence (CHEF) effect, as revealed by first-principles simulations. At 1.5 wt% and pH 5.5, 1 self-assembles into nanofibers to form hydrogel Gel I. Since Cd2+ could actively participate in the hydrogelation and promote the self-assembly, we also successfully applied Gel I for visible detection and absorption of Cd2+. With these excellent properties, Gel I is expected to be explored as one type of versatile biomaterial for not only environmental monitoring but also for pollution treatment in the near future