| Fluorescence imaging analysis is a detection method developing rapidly.Compared with traditional imaging analysis methods,it has higher sensitivity,more convenient detection process,etc.It is currently widely used in the field of life sciences,which also provides a powerful means for revealing the mysteries in living organisms.With the rapid development of fluorescence imaging analysis technology,traditional organic fluorescent dyes can no longer meet the needs of current scientific research goals,and thus many dye workers are constantly developing new organic fluorescent dyes with excellent application prospects.Among many organic fluorescent dyes,cyanine fluorescent dyes have the advantages of high molar extinction coefficient,large fluorescence quantum yield,tunable absorption and emission wavelength of the dye,and wide tuning range.Thus they are widely used in the fields of medicine and environmental science.Ho wever,traditional cyanine fluorescent dyes have many problems,such as:(1)large detection errors caused by poor stability and signal intensity changes over time;(2)reduction of imaging signal-to-background ratio and obvious decrease of detection limit caused by small Stokes shift of the dye and strong background signal;(3)The optical performance is greatly affected by the environment,and it is susceptible to signal fluctuations caused by the changes in the microenvironment,leading to inconsistencie s between the detection results and the actual situation.These problems not only severely limit the further application of cyanine dyes in biological imaging,but also are not conducive to the research of fluorescent imaging technology to further reveal l ife processes.Therefore,the development of new cyanine-based organic fluorescent dyes with excellent properties is still of great significance.In this paper,starting from the molecular luminescence mechanism and the improvement of chemical structure,s everal new types of cyanine dyes based on the combination of quinoxaline pyran structural units and cyanine dye structures are constructed,and some new approaches to solve the problems of most of cyanine dyes are proposed.The specific research contents are as follows:First,for the problem of small Stokes shift of the traditional cyanine dyes,we introduced a quinoxaline unit with strong electron-donating ability to break the "limit" effect of the cyanine and obtain a new type of cyanine dyes with a la rge Stokes shift.At the same time,the degree of charge transfer within the molecule of cyanine dye was enhanced,and its sensitivity to polarity was greatly improved,so as to realize the sensitive detection of polarity changes in biological environment.Secondly,in view of the problems such as poor stability and serious aggregation of the near-infrared II cyanine dyes,we successfully constructed a new type of near-infrared II dyes by introducing quinoxaline pyran structural units with large steric hindrance and strong electron donating cyanine fluorescent dyes.Spectral data show that under physiological conditions,this type of dye not only has good antisolvent quenching properties,but also exhibits excellent chemical stability and light stability.In addition,due to the strong electron-donating ability of quinoxaline pyran structure,compared with traditional cyanine dyes,the absorption and emission wavelengths of the new cyanine dyes also show a great red shift,and their maximum absorption and emission wavelengths are respectively red-moved to 1112 nm and 1181 nm,which is much longer than the near-infrared II cyanine dye with the longest absorption and emission wavelength(based on Cy7 structure)currently reported.These characteristics indicate that the new cyanine dyes will have great application potential in near-infrared II bioimaging. |
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