Tuesday, 14 June 2022

Real-time cell tracking: far-red DRAQ9

A DRAQ™ probe negative for the nucleus?  Whatever next!

DRAQ9™ is the latest product to come out of BioStatus's R&D.  It's very different from what you're used to seeing from us however, as DRAQ9™ is nuclear-negative yet plasma membrane permeant and famously far-red fluorescing!  

This remarkable and unexpected combination of features means that it has very low toxicity and cells can be grown on with DRAQ9™ present in the culture medium (CM) for many days.   This gives it great potential as a cell-tracking probe as the staining remains highly stable and consistent.  

Essentially, DRAQ9™+ cells look like doughnuts (aka donuts!) and have a characteristic peri-nuclear "signet-ring" patterning to the staining in the cytoplasm.  However, if cells are migrating then the pattern has a more directional emphasis, where there appears to be an accumulation of vesicles towards the leading edge of each cell.

DRAQ9™ can also provide a general cytoplasmic stain.  For example it has been used in development of a method for cytometry of reaction rate constant (CRRC) in motile cells (Yosief et al. 2022), added at 2┬ÁM for 30 minutes.

DRAQ9™ is compatible with time-lapse experiments to follow cells over several days due to its cell permeance, ultra-low toxicity and cytoplasmic labeling.  DRAQ9™ can be retained in the culture medium to maintain the staining, unlike the use of a dilution dye such as CFSE to follow division progeny.

Flexible & Safe
DRAQ9™ can be combined with DRAQ7™ to permit reporting of cell death in real-time.  Although these are both far-red fluorescing the are located in different compartments and with the bright DRAQ7™ signal only being present in cells with compromised plasma membranes (i.e. most typically late apoptotic, necrotic, dead cells).  DRAQ7™ can also be present in the CM for the duration of the imaging experiment, as has been reported in many papers over the last few years.

The enormous benefit for on-going cell health is that monitoring with red excitation has the least likely impact on DNA integrity compared to UV, for example and this is so for these two reagents being used in tandem, from one excitation source and emission channel, separated by cell patterning.

DRAQ9™’s far-red emission ensures that it is widely compatible with visible-range chromophores such as CFP, GFP and RFP.  DRAQ9™ is not photo-bleached or chemically unstable in culture media.

Further, DRAQ9™ cells can be fixed to capture information and combine with other end-point analyses.  You can read more about using DRAQ9 as a cell paint here.

You can find everything about DRAQ9™on the dedicated product page

Yosief, Robel, Giammarco Nebbioso, Vasilij Koshkin, Yumin Qiu, Chun Peng, Vadim Elisseev, and Sergey Krylov. "Making Cytometry of Reaction Rate Constant (CRRC) Applicable to Motile Cells." (2022). Preprint on ChemRxiv, 21 April 2022. DOI:10.26434/chemrxiv-2022-gtgzf