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.