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A naphthalimide-rhodamine probe for detecting Hg2+ was designed based on FRET mechanism, and the application in bioimaging and keypad lock were studied. [Display omitted] • A ratiometric and colorimetric probe of Hg2+ based on naphthimide and rhodamine was synthesized. • The detection mechanism had been verified by NMR, ESI-MS and HPLC spectra. • The probe can be used to construct molecular keypad lock and cell imaging. A novel FRET-based ratiometric fluorescent probe (Ro1) based on rhodamine and naphthalimide groups was designed and synthesized. The probe displayed high selectivity and sensitivity to Hg2+ and the significant color changed from yellow to pink could enable naked-eye detection of Hg2+. Ro1 also showed rapid respond to Hg2+ within 60 s with the limit of detection was 0.75 μM. The possible mechanism of probe Ro1 for detecting Hg2+ was investigated by using 1H NMR, ESI-MS and HPLC spectra. Further, Ro1 was designed as a molecular keypad lock with different sequences of Hg2+ and Cu2+ chemical input. Moreover, fluorescence imaging experiment of Hg2+ in living Hela cells demonstrated its potential applications in biological systems. [ABSTRACT FROM AUTHOR]

The fluorescent probe, GXY-ADP-2, with xanthene structure as the fluorescent core was designed and prepared for the selective detection of peroxynitrite (ONOO−). ONOO− can be produced endogenously and exogenously and is a strong oxidant with a short half-life. Oxidative modifications of biomolecules, that can be attributed to the formation of ONOO−, occur in the reactions of biomolecules with secondary ONOO−-derived radical oxidants. Therefore, it is very important to develop a specific fluorescent probe for detecting ONOO− to monitor oxidative stress state. The excitation wavelength and emission wavelength of the probe are 689 nm and 739 nm respectively. In the process of co-incubation with ONOO−, generate a new substance with two internal conjugated structures through a special reaction mechanism, one giving the fluorescence with the excitation wavelength of 347 nm and the emission wavelength of 484 nm with the detection limit of 0.12 μM, and the other that with the excitation wavelength of 433 nm and the emission wavelength of 583 nm with the detection limit of 0.077 μM. The linear dynamic range of the probe is 0–5 μM. Its response is not affected by the other reactive oxygen species, thus can sensitively detect ONOO−. In bioimaging experiments with HepG2 cells, the green and blue cell fluorescence signals (583 nm and 433 nm, respectively) were increased, while the red one (739 nm) was significantly reduced, under lipopolysaccharide (LPS) induced oxidative stress, proving that the probe could sensitively detect ONOO− in living cells. This work provides a new tool for the dynamic changes of ONOO− and oxidative stress processes in biological systems. [Display omitted] • A new fluorescent probe, GXY-ADP-2, was developed for detection of ONOO−. • GXY-ADP-2 exhibited high specificity and sensitivity to ONOO−. • GXY-ADP-2 is a ratiometric fluorescent probe with three-channel fluorescence signal changed. • GXY-ADP-2 can detect the dynamic change of ONOO− in living cells. [ABSTRACT FROM AUTHOR]