Application Of Silicon Substituted Coumarins In Bioimaging Of Hydrogen Sulfide And Human Serum Albumin

In recent years,with the rapid development of laser confocal and fluorescence bioimaging technology,bioimaging plays an important role in various fields,including chemistry,environmental science,biology,medicine,and pharmacy.Fluorescent probes are crucial in the development of fluorescence bioimaging technology.One of the most important parts to realizing this technology of biological fluorescence imaging relies on the design and synthesis of organic small molecule fluorescent probes.Researches have shown that the silicon element of the fourth main group can be used to replace the bridging oxygen in the xanthene structure.The resulted Si-substituted fluorophores bear many advantages such as the maximum absorption and maximum emission wavelengths located in the near-infrared region(NIR)with reliable photostability.The substitution of bridging oxygen atom with silicon atom is an important approach of regulating the spectra and photophysical and chemical properties of fluorescent dyes.In this dissertation,we designed and developed a group of novel silicon-substituded coumarins by replacing the bridging oxygen atoms in conventional coumarins with silicon atoms,and constructing silicon-based coumarin fluorescent probes SiC-Azs and HSAs.The probes are evaluated by spectral analysis and bioimaging experiments.Fluorescent probe SiC-Az2 can quickly monitor the changes of H₂S levels in organisms.Probe HSA-7 can be used to monitor exogenous human serum albumin(HSA)in cells.The details are the followings:(1)Synthesis of silicon-substituted coumarin derivativesSilicon-substituted coumarin belongs to a typical molecular fluorophore with a D-?-A electronic structure.We use the coupling reaction of iodine-substituted silicon-based coumarin and introduce strong electron withdrawing on the silicon-based coumarin skeleton(SiCs).Modification of its structure using different functional groups,a series of SiC derivatives have been designed and synthesized.In addition,the photostability and solvation effects of the SiCs on their spectra are evaluated.Structural modification can significantly improve the photophysical and chemical properties of silicon-substituted coumarins:including emission spectra,hydrophobicity,and photostability.(2)SiC-based human serum albumin(HSA)probesHuman serum albumin(HSA)is one of the most abundant proteins in plasma and plays a vital role in various physiological processes.Relatively strong background interference,limited selectivity,and weak to moderate signal response are still the main obstacles to conventional HSA probes.Our work designed and synthesized a series of silicon-based coumarin molecular fluorescent probes HSAs with high selectivity and high fluorescence response signal.After the binding of probe HSA1-7 and protein(HSA),the fluorescence intensity increases significantly.HSA-7 has provided extremely low fluorescence background and high signal-to-noise ratio.Competitive experiment results indicate that HSA-7 is likely to bind to both sites.(site I and site II).The probe was successfully applied in the bioimaging of exogenous HSA in cells.(3)SiC-based Hydrogen sulfide fluorescent probeHydrogen sulfide(H₂S)is an important component of reactive sulfur species(RSS).H₂S plays a vital role in regulating the redox state of cells and many basic signal transduction processes involved in many diseases.The azide reduction process is highly selective,but its kinetics is relatively slow,which has certain limitations for detecting active sulfur species in organisms.Therefore,this work designed and synthesized three silicon-based coumarin fluorescent probes SiC-Azs with ultrafast kinetics for detecting H₂S in vivo.The probe SiC-Az2 has ultrafast kinetics(25 s),a wide linear range(5.0-450.0?M)and a low detection limit(0.30?M)for the detection of hydrogen sulfide under physiological conditions.In this dissertation,we mainly focus on the design and synthesis of silicon-based coumarins(SiCs)and SiC probes.We have designed and synthesized a series of SiC derivatives SiC-Azs,SiC-Ams,HSAs.We studied their spectroscopic properties,used the probe SiC-Az2 to detect hydrogen sulfide ultrafast,used the probe HSAs to detect human serum albumin with high selectivity.We resepectively applied SiC-Az2 and HSA-7 to the biological fluorescence imaging.