Image of SYTO® 59 Red Nucleic Acid Stain packaging

Nuclear stain for eukaryotic and prokaryotic cells

The cell-permeant SYTO® 59 nucleic acid stain exhibits bright red fluorescence upon binding to nucleic acids. In both live and dead eukaryotic cells, SYTO® 59 generally shows cytoplasmic or mitochondrial as well as nuclear staining. In addition, SYTO® 59 will stain most live and permeabilized bacteria.

This protocol can be used for:

  • Nucleic acid (nuclear) staining in fluorescence microscopy

This protocol should not be used for:

  • Flow cytometry

You will need the following for this protocol:


1. Culture cells in an appropriate medium and vessel for fluorescence microscopy.
2. Remove the medium.
3. Wash the cells 1–3 times in a phosphate-free buffer to remove the medium.
4. Prepare the SYTO® 59 staining solution by diluting the stock solution 1:1,000 (5 µM) in a phosphate-free buffer.
5. Add sufficient staining solution to cover the cells.
6. Incubate for 30 minutes, protected from light.
7. Remove the staining solution.
8. Wash the cells 3 times in a phosphate-free buffer.
9. Image the cells.
Spectral information and storage
 SYTO® 59 
Excitation/Emission (nm)622/645
Standard filter setCy®3.5
EVOS® Light CubeTexas Red®
Storage conditions≤–20°C


Protocol tips

  • Warm to room temperature and briefly centrifuge the DMSO solution to the bottom of the vial each time before use.
  • Try multiple dye concentrations in the range from 100 nM to 5 µM to determine the optimal concentration.
  • In general, the best results are obtained in buffers that do not contain phosphate, such as Hank’s Balanced Salt Solution (14025092).
  • Treat all nucleic acid binding dyes as potential mutagens and handle with care.

nuclear staining of BPAECs
Nuclear staining of BPAECs. BPAECs were cultured, stained with SYTO® 59 dye (5 μM for 5 min), and then imaged.