Design, Synthesis And Application Of Novel Colorimetric And Fluorecent Dual-channel Probes

The biologically important substances including reactive oxygen species(ROS), reactive nitrogen species(RNS), and reactive sulfur species(RSS) play important roles in maintaining the biological redox homeostasis in physiological matrices. Concentration levels and distributions of these species are crucial to the living systems, and have been directly linked to some diseases and cancers. Therefore, sensitive visualization determination of biologically important species is very important to disclose their detailed functions and mechanisms in living systems and prevent numerous diseases.Among the various techniques, optical methods containing colorimetric and fluorescent probes are of current interest for the determination of biologically important species. Colorimetric probes are popular due to their capability to detect analytes by the naked eye without the help of any expensive instruments. The use of fluorescent probes has its apparent advantages in sensitivity, operational simplicity, most importantly, in real-time visual detection of targets in vivo, even in single living cells, with the help of confocal microscopic imaging. Additionally, ratiometric measurements permit signal rationing and thus increase the dynamic range and provide built-in correction for environmental effects.In this thesis, based on the sensing mechanism of optical probes, a series of new colorimetric and fluorescent dual-channel probes were designed, synthesized and applied to the determination of biologically important substances including nitroxyl(HNO), hydrogen peroxide(H2O2), hydrogen sulfide(H2S), and sulfur dioxide(SO2) derivates bisulfite(HSO3-) and sulfite(SO32-). The details are as follows:Based on internal charge transfer(ICT) mechanism, a simple 4-hydroxynaphthalimide-based colorimetric and ratiometric fluorescent dual-channel probe employing the 2-(diphenylphosphino)benzoate moiety as a recognition receptor for the detection of HNO with a large red-shifted emission was designed and synthesized. Our proposed probe exhibits high HNO-selectivity even in the presence of high concentration GSH and ascorbate, which is ascribed to the adoption of a 2-(diphenylphosphino)benzoate moiety. In addition, the probe displays a 104 nm red-shift of absorption spectra and the color changes from colorless to yellow upon addition of HNO, and thus can serve as a “naked-eye” probe for HNO. Importantly, our proposed probe can detect HNO quantitatively(2 ~ 35 μM) by ratiometric fluorescence method with a 128 nm red-shifted emission with excellent sensitivity(detection limit: 0.5 μM). The large(128 nm) red-shifted emission is very important to enhance the resolution of ratiometric bioimaging.A novel ICT-based ratiometric visual and far-red fluorescent probe(HNO-TCF) containing 4-hydroxystyrene-TCF fluorophore and a recognition receptor of 2-(diphenylphosphino)benzoate moiety for the rapid and ultrasensitive detection of HNO in living cells was developed. HNO-TCF exhibits high HNO-selectivity even in the presence of ROS, RNS, and high concentration biological reductants including glutathione(GSH), hydrogen sulfide(H2S) and ascorbate(AA), which might be ascribed to the adoption of the 2-(diphenylphosphino)benzoate recognition moiety. ICT-based fluorescent probe HNO-TCF displays a large(185 nm) red-shifted absorption spectrum and the color changes from yellow to blue upon addition of HNO. In addition, the results showed that HNO-TCF could quantitatively detect HNO in the range of 0 to 4 μ M with the detection limit of 10 nM by ratiometric visual and fluorescent spectrometry methods. Importantly, HNO-TCF was successfully applied to the fluorescence imaging of HNO levels in living cells, and it is expected to be a useful chemical tool for investigating the detailed functions and mechanisms of HNO in living systems.An ICT-based colorimetric and ratiometric fluorescent dual-channel probe for the detection of H2O2 with a large red-shifted emission was designed and synthesized. Our proposed probe exhibits high H2O2-selectivity over various analytes, which is ascribed to the adoption of a boronate moiety. In addition, the probe displays an 81 nm red-shift of absorption spectra and the color changes from colorless to yellow upon addition of H2O2, and thus can serve as a “naked-eye” probe for H2O2. Importantly, our proposed probe can detect H2O2 quantitatively by ratiometric fluorescence method with a 100 nm red-shifted emission with excellent sensitivity. The large(100 nm) red-shifted emission is very important to enhance the resolution of ratiometric bioimaging. Preliminary bioimaging application and low cytotoxicity investigations further demonstrated that the proposed probe would be of great benefit to biomedical researchers for investigating the detailed biological function of H2O2 in biological systems.Based on the double nucleophilicity of H2 S, a highly selective colorimetric and fluorescent dual-channel probe employing a receptor of 2-formylbenzoate moiety with two electrophilic reaction sites for H2 S was designed and synthesized. The addition of H2 S resulted in the color changes from colorless to yellow-green in aqueous solution, and thus the probe could serve as a “naked-eye” indicator for H2 S. Moreover, our proposed probe could be used to detect H2 S quantitatively in a wide concentration range(0 ~ 1000 μ M) by the fluorescence turn-on method with a detection limit of 2.4 μ M. Additionally, the probe showed excellent selectivity for H2 S over other various species including GSH, which might be ascribed to its two electrophilic reaction sites and the dual nucleophilicity of H2 S. Preliminary fluorescence bioimaging experiments demonstrated that the probe was cell-permeable and capable of visualization of H2 S levels in living cells.Based on the strong nucleophilicity of bissulfite to the electron-poor C=C double bond, we designed and synthesized a long-wavelength colorimetric and fluorescent dual-channel probe for the rapid detection of HSO3- with excellent sensitivity in aqueous solution and living cells. The addition of HSO3- resulted in the decrease of absorbance, accompanying with the color changes from blue to colorless, and thus our proposed probe could serve as a “naked-eye” probe for HSO3-. Moreover, the probe could be used to detect HSO3-quantitatively in the concentration range(0 ~ 10 μ M) with a detection limit of 0.1 μ M by the fluorescence spectrometry method. Importantly, our proposed probe exhibited excellent selectivity for HSO3- over other various species including Cys, GSH, S2-, SO32-, and ROS, which might be ascribed to the introduction of a receptor of electron-poor C=C double bond for HSO3-. Preliminary fluorescence bioimaging experiments and low cytotoxicity of our proposed probe in living cells demonstrated its potential of visualization of HSO3- levels in living systems.An ICT-based 4-hydroxynaphthalimide-derived colorimetric and ratiometric fluorescent dual-channel probe employing a levulinate moiety as high selective recognition receptor for sulfite was designed and synthesized. The probe showed a 100 nm red-shifted absorption spectrum accompanying with the color changes from colorless to yellow, and thus can serve as a “naked-eye” probe for sulfite in the food, beverages and drugs. Additionally, our proposed probe exhibited a large(103 nm) red-shifted fluorescence emission upon addition of sulfite, and could detect quantitatively sulfite by the ratiometric fluorescence spectroscopy method with high sensitivity. Further, the application of probe 1 in real water samples exhibited that our proposed probe would offer an excellent assay for the determination of sulfite in aqueous environment.