New fluorogenic dyes for analysis of cellular processes by flow cytometry and confocal microscopy

•Spectral properties of unsymmetrical monomethine cyanine dyes, containing quinazolinium moiety have been investigated.•The ability of dyes to stain live or apoptotic cells were examined by flow cytometry and confocal laser scanning microscopy.•The dyes are suitable for analysis of cell viability, apoptosis and cell cycle at low concentrations.

Fluorescent microscopy and fluorescent imaging by flow cytometry are two of the fastest growing areas in the medical and biological research. Innovations in fluorescent chemistry and synthesis of new dye probes are closely related to the development of service equipment such as light sources, and detection techniques. Among compounds known as fluorescent labels, the cyanine-based dyes have become widely used since they have high excitation coefficients, narrow emission bands and high fluorescence upon binding to nucleic acids.The key methods for evaluation of apoptosis and cell cycle allow measuring DNA content by several flow cytometric techniques.We have synthesized new monomethine cyanine dyes and have characterized their applicability for staining of live and/or apoptotic cells. Imaging experiments by flow cytometry and confocal laser scanning microscopy (CLSM) have been also performed. Two of the dyes have shown high-affinity binding to the nuclei at high dilutions, up to 10−9 M. Flow cytometry and CLSM have confirmed that these dyes labeled selectively non-living, e.g. ethanol-fixed cells that makes them appropriate for estimations of cell viability and apoptosis. The novel structures proved to be appropriate also for analysis of the cell cycle.