Highly Fluorescent Distyrylnaphthalene Derivatives as a Tool for Visualization of Cellular Membranes

Fluorescent imaging, which is an important interdisciplinary field bridging research from organic chemistry, biochemistry and cell biology has been applied for multi-dimensional detection, visualization and characterization of biological structures and processes. Especially valuable is the possibility to monitor cellular processes in real time using fluorescent probes. In this work, conjugated oligoelectrolytes and neutral derivatives with the distyrylnaphthalene core (SN-COEs) were designed, synthetized and tested for biological properties as membrane-specific fluorescent dyes for the visualization of membrane-dependent cellular processes. The group of tested compounds includes newly synthesized distyrylnaphthalene derivatives (DSNNs): a trimethylammonium derivative (DSNN-NMe₃⁺), a phosphonate derivative (DSNN-P), a morpholine derivative (DSNN-Mor), a dihydroxyethylamine derivative (DSNN-DEA), a phosphonate potassium salt (DSNN-POK), an amino derivative (DSNN-NH₂) and pyridinium derivative (DSNN-Py+). All compounds were tested for their biological properties, including cytotoxicity and staining efficiency towards mammalian cells. The fluorescence intensity of SN-COEs incorporated into cellular structures was analyzed by fluorescence activated cell sorting (FACS) and photoluminescence spectroscopy. The cytotoxicity results have shown that all tested SN-COEs can be safely used in the human and animal cell studies. Fluorescence and confocal microscopy observations confirm that tested COEs can be applied as fluorescent probes for the visualization of intracellular membrane components in a wide range of different cell types, including adherent and suspension cells. The staining procedure may be performed under both serum free and complete medium conditions. The presented studies have revealed the interesting biological properties of SN-COEs and confirmed their applicability as dyes for staining the membranous structures of eukaryotic cells, which may be useful for visualization of wide range of biological processes dependent of the extra-/intracellular communications and/or based on the remodeling of cellular membranes.