Merocyanine and coumarin fluorescent probes represent an important class of labels widely used for the visualization of various cellular organelles. Both types allow conjugation with other molecules or the introduction of different functional groups, enabling precise tuning of absorption and emission wavelengths. These two classes of fluorophores also support the attachment of organelle-targeting groups, such as triphenylphosphonium for mitochondrial targeting or weakly basic groups for lysosomal labelling.
The aim of this master's thesis was the development of fluorescent probes for labelling membranes, lysosomes, the endoplasmic reticulum, and mitochondria. Coumarin derivatives bearing a trifluoromethyl group, which facilitates a larger Stokes shift, were used alongside merocyanines emitting in the red or near-infrared (NIR) region. Targeting moieties were either integrated directly into the fluorophore structure or introduced via CuAAC click chemistry onto alkyne-functionalized probes. Excitation and emission spectra were recorded for selected compounds.
Coumarin fluorophores were successfully functionalized with a sulfonamide group. In merocyanines, modification of electron-donating and electron-withdrawing groups enabled a red-shift in spectral properties. The prepared probes, based on both coumarin and merocyanine scaffolds, selectively localized to the intended cellular organelles. Spectral analyses showed that coumarin functionalization had minimal impact on fluorescence, whereas the electronic properties of substituents significantly influenced the optical characteristics of merocyanines.
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