| In recent years,bio-imaging technology has become a very powerful tool for the detection of life activities in the body,fluorescent dyes have greater advantage because of their high sensitivity,ease of operation and other characteristics.In the present report,the absorption and emission of most fluorescent dyes were located in the visible region,which largely limited their application in biological detection.This is because the biological tissue has strong absorption of visible light and strong autofluorescence,visible light is absorbed by biological tissue,resulting in light dispersion and biological tissue penetration weakened,and biological tissue's strong autofluorescence is mainly located in the visible area,which poses large background interference to the detection.Different from these dyes,the fluorescent dyes that absorption and emission located in near infrared region?NIR,650-900 nm?have great advantage in biological detection.Compared with visible light,the near-infrared light has a small background light interference,better biological organization penetrating ability,less damage to biological tissue and other advantages.Now,NIR fluorescent dyes current as a new field have been widely studied and applied.The development of near infrared fluorescent dyes with high fluorescence quantum yield,better biocompatibility and low cytotoxicity is the key to the development of biomedical imaging technology.In this paper,several near-infrared fluorescent dyes for detection were designed and synthesized,and their optical properties were studied in detail.The main work can be divided into the following three parts:?1?Three kinds of near-infrared pH fluorescent dyes based on benzo[a]phenoxazine were designed and synthesized.Due to the equilibrium between benzo[a]phenoxazine and benzo[a]phenoxazinium under neutral and acidic conditions,the fluorescence properties also changed,dyes 4a-c had different optical properties.The difference between the structures of dyes 4a-c was the pyridine substituents,dyes 4a and 4b were ethyl and hydroxyethyl groups respectively,and their fluorescence properties were similar,they were"OFF-ON"fluorescent dyes.The pyridine substituent of 4c was morpholine,different from4a and 4b,dye 4c was ratiometric fluorescent dyes.In addition,the pKa values of the dyes4a-c are small and dyes 4a-c are suitable for working in extreme acid conditions.Fluorescence imaging experiments showed that 4c was a fluorescent dye with lysosomal targeting ability.?2?One novel near-infrared cyanine dye 7 was designed and synthesized by hybridizing benzopyrylium and indole.Compared with the traditional cyanine dyes,dye 7 has some excellent properties:good water solubility,good light stability,near infrared emission and so on.Because benzopyrylium was prone to addition reactions with H2S,the dye optical responses to H2S were tested.The sensitivities of the dye 7 to H2S were text in the range of0-10 equiv.NaHS,experimental results showed that dye 7 was“OFF-ON”fluorescent dye and the detection limit was 0.168?M.So dye 7 could be applied to detect H2S in the organism.?3?Three kinds of pH fluorescent dyes 15a-c were designed and synthesized by using benzopyrylium-indole hybrid and benzopyrylium-coumarin hybrid fluorophores.Due to the protonation of aniline under acidic conditions,the three dyes exhibited different optical properties respectively.Dye 15b was constructed with benzopyrylium and indole parts by the conjugated double bonds,while dye 15a was containing a non-conjugated cyclic structure,so the fluorescence properties of dyes 15a-b showed a diametrically opposite change with similar absorption spectra of them.Because molecular conjugate structure of dye 15c was stronger than 15a-b,it showed"OFF-ON"type response with pH value change.The optical properties of the dyes 15a-c had also been explained and verified by theoretical calculations.In addition,the pKa values of the dyes 15a-c are also small and they are also suitable for working in extreme acid conditions. |
PDF Full Text Request