determines the code number of the bead this allows discrimination of signals from a multitude currently up to 200 of beads with different codes which provides for the exceptional multiplexing capacity of the bioplex biorad bulletin 2890 as a result of this design fluorescence signals from ordinary cells cannot be measured on the bioplex directly because the cells do not produce a recognizable red infrared fluorescence code however additional staining of the cells with an appropriate red infrared fluorescent dye s can overcome this hurdle we found that common staining dyes such as trypan blue tb and crystal violet cv when used at low concentrations were able to u2018 code u2019 target cells such as mdck and vero mammalian kidney epithelial cultures or avian erythrocytes tb a dark blue staining dye is commonly used in the dye exclusion method where apoptotic cells with damaged surface membranes take up the dye turning dark blue while normal cells do not however it is also true that normal cells become weakly stained with tb on their surface which is normally not observable by light microscopy as used in the dye exclusion assays tb possesses a weak red infrared fluorescence and surface staining of normal and healthy cells with tb occurs sufficient for their recognition by the classification system of the bioplex reader as readable objects damaged and dying cells carry higher loads of tb which results in stronger red infrared fluorescence and accordingly different.