CytoTell® Blue is a blue fluorescent cell proliferation indicator developed for monitoring cell division and long-term tracking of live cells by flow cytometry and fluorescence microscopy. As cells divide, the dye is distributed equally between daughter cells, resulting in progressive halving of fluorescence intensity that enables visualization of successive cell generations. CytoTell® Blue exhibits peak excitation around 405 nm and peak emission around 450 nm, making it compatible with violet laser excitation and detection using 450/20 bandpass filters commonly used for Pacific Blue® or BD Horizon® V450 channels.

CytoTell® Blue was developed for multicolor applications where CFSE and other fluorescein-based proliferation dyes are not suitable due to spectral overlap with GFP or FITC-labeled antibodies. The dye exhibits minimal cytotoxicity and provides spectral separation from fluorescein-based probes for multiparameter cell analysis. CytoTell® Blue-labeled cells may be fixed and permeabilized for intracellular target analysis using standard formaldehyde-containing fixatives and saponin-based permeabilization buffers, making the dye suitable for downstream intracellular staining workflows and multicolor flow cytometry applications.