Fluorescence detection is a highly sensitive method that is increasingly used in life sciences and research. It is a phenomenon in which the electrons of a fluorophore are excited by light of a specific wavelength to go to a higher excited singlet energy state. After a few nanoseconds, the electrons spontaneously return to their ground state and release excess energy in the form of fluorescence, which we can detect. For fluorescence imaging, we need photostable fluorophores with high quantum yields and high molar extinction coefficients. At the same time, fluorophores must have sufficient specificity for target molecules and large Stokes shifts. Since such fluorophores are rare, further research and discovery of new fluorophores is very important. In our master thesis we focus on the synthesis of fluorescent probes for labeling lipophilic structures.
In the first part, we focus on the synthesis of coumarin derivatives, which are of particular interest for the labeling of lipid droplets. Lipid droplets are cellular organelles found in all eukaryotic cells, and much remains to be understood about them. Numerous studies have shown that the accumulation of lipid droplets in the body is related to the occurrence of certain diseases, making research tools such as fluorophores highly desirable. As part of our master's thesis, we were able to synthesize two promising fluorescent probes for labeling lipid droplets (products 8 and 13). Compound 13 is more interesting than compound 8 due to the large Stokes shift, but the potential cytotoxicity of the compounds should be investigated. In the second part of the master's thesis, we synthesized lipophilic ligands, which were then combined with europium, terbium, and/or dysprosium to form complexes. Lanthanide complexes are very good fluorophores, mainly due to their large Stokes shift and very narrow emission spectra. As part of the master's thesis, we were able to synthesize a few different fluorophores with lanthanides, but they all had the same problem. When analyzed, the compounds were not soluble in DMSO and therefore could not label cellular structures. Fluorophores glow well, but it is necessary to find a suitable solvent and study their properties. The Jožef Stefan Institute staff will continue to try to dissolve the complexes in absolute ethanol and analyze the usefulness of our compounds.
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