Design, Synthesis, Optical Properties And Application Research Of Novelsmall Molecular Fluorescent Probes

As an important indicator of the cellular health, pH plays a significant role in the cell growth, proliferation, apoptosis, autophagy, ion transport and other cellular process. The minor variations of intracellular pH may cause cellular dysfunction and serious diseases, such as colorectal cancer, breast cancer, cystic fibrosis, neurodegenerative disorders even Alzheimer’s disease. Although organelles with acid are important for the human health, the research on them is far from enough. Therefore, developing acid pH fluorescent probes for the detecting of the concentration and distribution of H+ within cells has become extremely urgent.Hg2+ has a great influence in the industrial, medicine and cosmetics research process. Meanwhile, as an environmental pollutant, Hg2+ routinely comes from the amalgam treatment, coal-fired power plants, waste incineration and commercial production. Considering both the physical and environmental harm of mercury pollution, the detection of Hg2+ is imminent.Hydrazine is well applied in the synthesis of various chemical materials, such as pharmaceuticals intermediates and plastics polymers. While as a kind of high-energy fuel, hydrazine is used for the propellant missiles, satellites and rocket propulsion systems. However, hydrazine dissolved in water easily and can be readily absorbed to cause severe damage to the kidneys, lungs and central nervous system. Therefore, a detection method for hydrazine with high sensitivity and selectivity was significant to the study of the physiological and pathological process of the cells.Combined the property of the analytes with the optical characteristics and structure of the common fluorophores, fluorescent probes were designed and synthesized for the detection of pH, Hg2+ and hydrazine respectively based on the rhodamine, dansyl and coumarin fluorophores. We have further explored the optical properties and dedicated to the applied research of them in the cells and water samples. The concrete content includes the following three parts: 1. Design, synthesis, optical characteristics and application research of pH fluorescent probes based on rodamine B fluorophoreConsidering the spirocyclic form of the rhodamine structure can switch to the open-cycle form and restore the large conjugate structure under the acid condition, we synthesized two pH fluorescent probes. One of the first was developed based on the rhodamine-rhodanine structure with pKa= 4.85 in buffer solution. The fluorescent intensity exhibited strong pH-dependent performance and responded linearly to minor pH fluctuations within the range of 4.2-5.2. To increase the solubility of the probe, the other was designed based on the quaternary ammonium salt form by introducing a positive charge, which have largely improved the property of the probe. In addition, both of the pH probes possess the excellent cell membrane permeability and could image weak acid pH changes of lysosome in live cells with excellent sensitivity, which demonstrated their great application value.2. Design, synthesis, optical characteristics and application research of Hg2+ and hydrazine fluorescent probes based on dansyl fluorophoreFirstly, we synthesized a Hg2+ probe based on the dansyl fluorophore and the strong chelating ability of both N and 0 atoms, which have been successfully used in the detection of Hg2+ in the Yellow River samples. Then combined with the Gabriel reaction, we also developed a hydrazine probe with the dansyl fluorophore. Upon the addition of hydrazine, Dansyl-NH2 with strong fluorescence was released accompanied by the maximum emission wavelength changed from 475 to 512 nm and the color of the solution changed from yellow to colorless, allowing the colorimetric detection of hydrazine. In addition, the probe could detect hydrazine vapor with TLC plates and the concentration of hydrazine in water samples and HeLa cells.3. Design, synthesis, optical characteristics and application research of hydrazine fluorescent probe based on coumarin fluorophoreIn this part, we synthesized a probe based on the coumarin fluorophore and ethyl trifluoroacetate structure, which achieved the detection of hydrazine both in weak acid solution and vapor state selectively and sensitively. With the limit of detection 8.32 ppb (2.6 × 10-7 M), the probe could well meet the request (<10 ppb) of the U.S. Environmental Protection Agency (EPA). Besides, due to the addition of hydrazine, the solution of probe exhibited a remarkable color change from pale green to light blue, which could be recognized with naked eyes and realized the colorimetry detection of hydrazine.