Near-infrared Fluorescent Probes with Long-acting Cyclic Monitoring and Effectively Eliminating Peroxynitrite.

Two through-bond energy transfer fluorescent probes with a dihydroxyl naphthyl-pyrenyl conjugated system were synthesized for long-acting cyclic monitoring and eliminating peroxynitrite (ONOO- ). The probes exhibit large Stokes shifts (230 or 280 nm) and the fluorescence at 620 or 652 nm rapidly change in response to continuously variable concentrations of ONOO- under physiological conditions. The probes show good reversibility and can rapidly monitor the concentration changes of ONOO- in real time. In addition, with the additions of the probes, the decomposition of ONOO- is greatly accelerated. Therefore, the probes can effectively eliminate the excess ONOO- as well as sensing it. The biological studies showed that the probes can effectively and reversibly eliminate both exogenous and endogenous ONOO- in-situ as well as sensing its changes in cells, which can help to maintain the normal physiological concentration of ONOO- in organisms. This is the first system that a probe achieves multifunction including real-time detection, long-acting cyclic monitoring and in-situ elimination, thereby maintaining a normal physiological balance for ONOO- .

A Silyl Ether Based Fluorescent Probe for Rapid Monitoring of Endogenous Peroxynitrite Concentration and Imaging in Living Cells through Multicolor Emission.

The peroxynitrite ion (ONOO- ) has important roles in many biological processes. We have developed a multicolor ONOO- -sensing probe (SiONNOH) that undergoes deprotonation and desilylation processes, which result in several changes in the emission wavelengths. In response to different concentrations of ONOO- , the probe exhibits fluorescence changes from pink (595 nm at 2 eq. ONOO- ) to green (540 nm at 6 eq. ONOO- ) via orange (3 eq. ONOO- ) and yellow (4 eq. ONOO- ) under physiological conditions until no fluorescence signal is observed after ONOO- is completely eliminated by lipoic acid. The probe shows the high selectivity for ONOO- and the limit of detection is calculated to be 1.27 µM. Moreover, the probe shows the capacity to monitor the concentration ranges of ONOO- through multicolor fluorescence in living cells, which will greatly facilitate the rapid detection of ONOO- concentration ranges by the naked eye under a UV light without any precision instrumentation.

A General Strategy for Through-Bond Energy Transfer Fluorescence Probes Combining Intramolecular Charge Transfer: A Silyl Ether System for Endogenous Peroxynitrite Sensing.

A general strategy is reported for developing through-bond energy transfer (TBET) fluorescence probes by combining intramolecular charge transfer (ICT). The strategy uses a coplanar donor-π-bridge-acceptor system (SiOPh-PyOH) without spirolactam. The off-on switch of TBET and ICT is controlled by coplanar structure changes in the sensing process instead of spirolactam ring-opening in traditional TBET probes. DFT calculations showed that the energy and charge transfers from SiOPh to PyOH are prohibited. Since the SiOPh has no fluorescence, the probe SiOPh-PyOH shows fluorescence properties similar to that of pyrene. After sensing ONOO- , the silyl ether is removed and the probe changes into - OPh-PyO- . Electron-donating ICT from OPh to PyO- induces a large redshift of emission to 594 nm (179 nm shift). TBET from OPh to PyO- ensures the probe exhibits a large pseudo-Stokes shift of 213 nm. Furthermore, the probe was successfully used in endogenous ONOO- detection. This study offers a new strategy for the construction of TBET probes emitting in the red region without spirolactam ring-opening, a new ONOO- sensing system using silyl ether as a reaction site, and a method for the deprotection of silyl ethers with ONOOH under mild conditions.

A visible-near-infrared fluorescent probe for peroxynitrite with large pseudo-Stokes and emission shift via through-bond energy and charge transfers controlled by energy matching.

We reported a visible-near-infrared fluorescent probe for peroxynitrite detection with large pseudo-Stokes and emission shifts, based on through-bond energy transfer (TBET) in combination with intramolecular charge transfer (ICT). Pyrene was chosen as a fluorophore (acceptor), which has monomer/excimer fluorescence characteristics. A conjugated 1,2-dimethylenehydrazine structure was a linker and phenyl boronate was selected as a reaction site (donor) to design the probe (Py-PhB) using the chemical transformation from boronate to phenol, which results in the increase of the energy of the donor to match the energy of the acceptor and simultaneously achieves TBET and ICT between the donor (phenolate) and the acceptor (pyrene), leading to a fluorescence 'OFF-ON' in a red-shifted region and a large emission shift. The results show that the probe exhibits high selectivity to ONOO- with a detection limit of 3.54 µM. Favorable ICT from phenolate to pyrene makes the probe possess a large monomer emission shift (183 nm), red-shifted to organe-red light (598 nm). TBET ensures the probe with a large pseudo-Stokes shift of 244 nm. Furthermore, its excimer emits a near-infrared light (720 nm), which is extremely beneficial for bioimaging. In short, this probe offers a novel design strategy for designing the TBET fluorescent sensors emitting red or NIR light with large pseudo-Stokes and emission shifts.