FAQ: Can cell-impermeable substrates be microinjected into cells, and how is the excess substrate exported?

Yes, SNAP-tag substrates can be microinjected into cells permitting live cellular imaging in the near infrared range by using substrates carrying the appropriate fluorophore. Excess substrate will be transported out. See Keppler A. et al. (2006) BioTechniques, 41, 167 for a systematic study.