New applications of Nobel Prize molecules: cyclopentadienyl compounds for imaging

Living cell imaging based on fluorescent probe has become an indispensable part of medical diagnosis and biological research Since its discovery, probes that can be used for fluorescent imaging of living cells have expanded from traditional organic dyes and metal ligand complexes to new fluorescent materials such as nanopolymers and nanoparticles These probes have good imaging performance, but they also face some problems, such as water solubility, pH stability, photostability, cell membrane permeability and biocompatibility However, the existing probe system can not solve the above problems at the same time, so it is urgent to develop a new fluorescent probe system Recently, J Fraser Stoddart, Professor of Northwestern University, academician of the Academy of Arts and Sciences and academician of the Royal Academy of Sciences, reported a new fluorescent probe and studied its application in the field of imaging Since more than 30 years ago, Professor Stoddart reported a kind of rigid host molecule, bluebox and its derivatives have been widely used in the research of host guest recognition, and have various applications in the extraction, catalysis, molecular machinery and other fields of polycyclic aromatic hydrocarbons However, there is no research on this kind of compounds in biological imaging The authors speculate that if these modifiable compounds have fluorescence characteristics, they are likely to be used in biological imaging Therefore, based on bluebox, the author synthesized a kind of cyclopentadienyl derivatives with asymmetric sides and successfully applied them to fluorescent imaging of living cells This achievement was published in the Journal of the American Chemical Society (DOI: 10.1021 / JACS 8b03066) under the title of "extzbox: a promising cyclone for live cell imaging" Fig 1 Synthesis process of compound 6.4x (photo source: J am Chem SOC.) compared with the traditional bluebox, the new cyclophane derivative not only has a larger cavity, but also has certain photophysical properties, but its synthesis method is basically the same as the traditional bluebox In the synthesis of traditional bluebox, bipyridine and its derivatives are used as the structural units on both sides, which react with 1,4-dibromomethyl or the like to form a ring-like product In order to introduce fluorescence properties and keep the length of the cyclopentadiene side units basically the same, thiazole group was introduced Firstly, the structural units 1 and 3 of the cyclopentadienyl side were obtained by the reaction of 1,4-dibromobenzene with 4-pyridylmethane and dithiocarboxyl, respectively; secondly, the structural units 1 and 2 equivalent 1, 4-dibromomethylbenzene reacts to obtain the intermediate product 5 of the half ring; finally, 5 and 3 react to form a ring to obtain cyclopentadienyl compound 6, and the water-soluble cyclopentanyl compound 6.4cl is further obtained by anion exchange In addition, in order to make a comparison in the following experiments, the author methylated structural units 1 and 3 to obtain 2.2cl and 4.2cl with positive charge Fig 2 A) the steady-state absorption and emission spectra of compound 6.4cl; b) the transient absorption spectra of compound 6.4cl; c) the cyclic voltammetric curves of compound 6.4cl (photo source: J am Chem SOC.) after obtaining compound 6.4cl, the author studied its photophysical and chemical properties: the steady-state absorption spectra showed that compound 6.4cl was in 320 There are obvious absorption at nm and 410 nm (Fig 2a) The two peaks correspond to two units (exbipy2 + and tzbipy2 +) in the structure respectively The steady-state emission spectrum shows that the aqueous solution of compound 6.4cl has strong fluorescence emission at 470 nm (Fig 2a) In addition, the study on the stability of compound 6.4cl shows that its photostability is equivalent to that of Hoechst 33258, which is a commercial nucleic acid dye, and the new dye can also keep stable in strong acid solution Fig 3 Cytotoxic test and biological imaging of compounds 2.2cl, 4.2cl and 6.4cl (photo source: J am Chem SOC.) since compound 6.4cl has good light stability and acid stability, and its fluorescence spectrum in serum is not much different from that in solution, the authors speculate that such compounds can be applied and biological imaging Before the cell test, the author first tested its cytotoxicity The results showed that compound 6 · 4CL showed very low toxicity at different concentrations (Fig 3) After that, we found that compound 6.4cl was mainly concentrated in the cytoplasm after entering the cell through co location test, and the final imaging test showed that compound 6.4cl could do cell imaging indeed Under the same conditions, compound 6.4cl does not quench in a short time, and its fluorescence intensity is as high as 6 times of 4.2cl In the end, the author said that although the experimental results preliminarily showed that the cyclopentadiene compound can be used in biological imaging, if we want to get better imaging results, the fluorescent probe needs to be improved in many aspects All authors: indranilroy, Sharan bobbala, Jiang Zhou, Minh T Nguyen, Siva Krishna Mohan nalluri, Yilei Wu, Daniel P Ferris, Evan Alexander Scott, Michael R wasielewski, Andre J Fraser Stoddart Corresponding author: J Fraser Stoddart J Fraser Stoddart, born in Edinburgh, UK in 1942, received his Ph.D from the University of Edinburgh in 1966, and is currently a professor of chemistry at Northwestern University Shared the 2016 Nobel Prize in chemistry with Jean Pierre Sauvage and Bernard L Feringa.