Rare Earth Complexes, Fluorescent Probes For Intracellular Imaging Of Small Molecular Species Analysis

Accompanied with the development of life science, people realizes many small and bioactive moleculer species play very important role in living cells, for example, active oxygen species(1O2, H2O2, O-2) and some metal ions (Mg2+, Ca2+, Zn2+, Cu2+). They are important mediators for the pathological conditions of various diseases. A rapid rise in intracellular oxidant levels under oxidative stress could cause damage to biological molecules and result in various diseases, such as carcinogenesis, inflammation, ischemia-reperfusion injury, and signal transduction. Therefore it is of great importance to achieve detection of the active small moleculer species in living cells. It is helpful to studying the relation between their physiological function and diseases. At present, Fluorescence imaging methods are widely used in living cells. Fluorescent probes that are used in imaging applications are mostly based on organic fluorescent dyes, such as fluorescein or rhodamine. But these dyes have some limitations, for example, they are prone to interference from light scattering in biological media and they have low photostability which lead to photobleaching. So it is of great importance to achieve fluorescence lifetime imaging and to solve the problem of photobleaching, which in order to improve the selectivity and sensitivity in the real time, dynamic and continuous detection. The applications of lanthanide complexes as fluorescent probes has caused much attention in biology because of their long fluorescent lifetime, sharp emission bands and large Stokes shift.At present, there are some reports about lanthanide complexes as fluorescent probes specific for some small and bioactive moleculer species in living cells mainly about the detection of singlet oxygen and zinc ion, but there are a few reports about fluorescence imaging based on lanthanide complexes. As fluorescent probe they must satisfy the following requirements: First, good water-solubility; Second, good thermal stability in physiological conditions; Third, good membrane penetrativity and have no toxicity to cells; Forth, long excitared wavelength and high quantum yield. When we design the probe we must consider all the factors in order to make its application in fluorescence imaging better. Recently, new water-soluble lanthanide complexes have been developed giving opportunities to novel applications, in heterogeneous and homogeneous immunoassays, DNA hybridization assays, determination of enzyme activities and ions. There is an exigent need for researchers to develop lanthanide-based fluorescent probes with high quantum yield, long fluorescent lifetime and good water-solubility.In this paper, we designed and prepared the intermediates of lanthanide complexes according to some correlative literature. The intermediate 4-bromo-6, 6′-bis(bromomethyl)-2,2′-bipyridine was prepared from 2-amino-6-picoline by diazotization, Ullmann Coupling Reaction, oxidation, nitration, bromination, deoxygenation, NBS bromination and so on. We used 4-bromo-6, 6′-bis(bromomethyl)-2,2′-bipyridine reacting with diethyl iminodiacetate to prepare tetraethyl 2,2′,2′′,2′′′-[(4-bromo-2,2′-bipyridine-6,6′-diyl) bis(methylenenitrilo)] tetrakis(acetate). Then we prepared the intermediate tetraethyl 2,2′,2′′,2′′′- [(4-p-tert-butyloxycarbonylaminobenzyloxy-2,2′-bipyridine-6,6′-diyl)bis(methylenenitrilo)]tetrakis(acetate) similar to the synthesis of diaryl ethers. During the experimentation, the condition of the synthesis was researched and the structure of the products were determined by the detection of melting point, 1HNMR, IR, MS and so on to prove the reliability of theses structures and synthetic methods.