Design And Synthesis Of Novel Carbon Monoxide,Nitroxyl And Hydrogen Sulfide Small Molecular Fluorescent Probes And Their Bioimaging

Fluorescent probe is widely applied in diverse fields such as the biological markers, environmental analysis, cell staining, clinical test and diagnosis due to its simple operation, high sensitivity, good reproducibility, good cell membrane permeability, and situ detection. In addition, by combining with fluorescence microscopy, fluorescent probe and bio-imaging can be exploited as a powerful approach to investigate biomolecules of interest with high temporal and spatial resolution. Fluorescent sensors are requisite molecular tools for sensing and bio-imaging. Comparing with the one-photon fluorescence probe, Two-photon microscope（TPM） provides an attractive technique to study biomolecules in living cells and tissues. TPM, where fluorescence is triggered by two-photon excitation, shows a variety of advantages. It can facilitate three-dimensional imaging of living tissues, reduce photodamage to biosamples, increase tissue penetration, negligible background fluorescence, which contribute to the capability of imaging in deep tissues and animals. However, it is still a big challenge to find fluorescent probes with favorable properties and significantly large two-photon action cross-section. In this dissertation, the main task is to design and modify organic fluorescent molecules, and construction two-photon fluorescence probe for carbon monoxide, nitroxyl, fluorescent probe for hydrogen sulfide. The specific contents include the following:（1） We rational design and synthesis of a unique carbazole-coumarin（CC-1⁷）-based two-photon fluorescent platform, in which the two-photon properties can be regulated by introducing a heavy atom or withdrawing group at the 4’-position of the coumarin moiety. Based on the two-photon platform, we further constructed the novel two-photon fluorescent carbon monoxide probe（CC-CO）. The probe exhibited high selective good cell membrane permeability to carbon monoxide,and work well in a wide p H range. We have further demonstrated that the first two-photon fluorescence turn-on probe（CC-CO） could stain carbon monoxide in cells and tissue slices.（2） we developed GCTPOC-1 as the first two-photon fluorescent turn-on nitroxyl probe by using GCTPOC as the two-photon platform and triarylphosphine as the reactive site for nitroxyl. The probe elicited a large fluorescence enhancement（49-fold） and exhibited high selective and sensitive, good cell membrane permeability to nitroxyl. We have further demonstrated that the two-photon fluorescence turn-on probe could stain nitroxyl in He La cells and liver tissue slices.（3） we report PI-N₃ as a new fluorescent chemosensor for hydrogen sulfite based on a phenanthroimidazole dye. The probe PI-N₃ elicited a large fluorescence enhancement（20-fold） and exhibited high selective and sensitive, good cell membrane permeability to hydrogen sulfite,and work well in a wide pH range. We envisioned that the fluorescence of the phenanthroimidazole dye may be markedly depressed due to the quenching effect from the electron-rich α-nitrogen of the azido group. We have further demonstrated that the chemosensor is suitable for monitoring variations of hydrogen sulfite levels in living He La cells.（4） Finally, we have developed a series of Bodipy derivaties as a novel near infrared（NIR） functional fluorescent dyes. we synthesize a novel NIR fluorescent probe NIR-H₂S to detect hydrogen sulfite based on H₂S-induced thiolysis of dinitrophenyl ether chemistry. The probe PI-N₃ elicited a large fluorescence enhancement（18-fold） and exhibited high selective and sensitive, low detection limit（5×10-8 M）, good cell membrane permeability to hydrogen sulfite,and work well in a wide p H range. Most importantly, we demonstrate that NIR-H₂S has the capability of imaging hydrogen sulfite in living He La cells.