The CyQUANT Direct Red Cell Proliferation Assay is a simple no-wash, add-and-read fluorescent microplate assay that can be used to assess cell growth, viability, or compound toxicity. The assay consists of a cell-permeant DNA-binding red fluorescent probe and a cell-impermeant background suppressor. The probe and suppressor are mixed and added to cells; the probe stains all cells, while the suppressor only enters dead cells or cells with compromised cell membranes, suppressing probe fluorescence in those locations. The result is that only healthy cells are detected.

CyQUANT Direct Red Cell Proliferation Assays features include:
• Convenient—no washes, cell lysis, or temperature equilibration; simply add and read to detect changes in adherent and suspension cell proliferation
• Accurate―based on amount of cellular DNA, which is highly regulated and independent of the metabolic state of the cells
• Robust―optimized red fluorescent probe and background suppressor result in a highly sensitive assay with a large dynamic range
• Stable―red fluorescent signal stability for seven hours, ideal for large screening assays
• Multiplex enabled―can be combined with spectrally distinct fluorescent or luminescent readouts

The CyQUANT Direct assay is a red fluorescence-based proliferation and cytotoxicity assay for microplate readers with a linear detection range from less than 100 to 20,000 cells per well for most cell types. The no-wash, add-mix-read assay can be completed in one hour. The red fluorescent excitation and emission wavelengths result in an assay that is ideal for multiplexing with green fluorescent dyes or proteins. Additionally, the fluorescent signal is stable for several hours, for additional workflow convenience.

Since the amount of DNA in cells is highly regulated, detection methods based on determining the amount of DNA are highly accurate. The CyQUANT Direct Red Cell Proliferation Assay consists of a red fluorescent cell-permeant DNA-binding probe and a background suppressor dye. The probe and suppressor are mixed, added to cells, incubated for one hour, and then the fluorescence measured. The probe enters all cells, but the suppressor only enters dead cells or cells with compromised membranes. Upon entering dead and dying cells the background suppressor dye suppresses the signal from the fluorescent probe, resulting in the detection of only healthy cells. Thus, the CyQUANT Direct Red assay can be used to measure changes in proliferation as well as cytotoxicity.