Safety testing of infracyanine green using retinal pigment epithelium and glial cell cultures

To undertake safety testing of infracyanine green (IFCG) in a cell culture model.

Experiments were undertaken in a cell culture model used previously to perform safety testing of indocyanine green (ICG). Human retinal pigment epithelium (RPE) and Müller cells were exposed to IFCG for 5 minutes, over a range of concentrations up to 0.5%. Experiments were repeated, using double-staining with trypan blue. Cell viability was measured at days 1, 5, and 15 using a mitochondrial dehydrogenase assay and a fluorescent live-dead probe containing calcein and ethidium homodimer-1. Viability was measured after exposure to 0.5% IFCG and 5 minutes of illumination with a vitrectomy endolight powered by a xenon light source.

RPE viability was not reduced over the range of concentrations and follow-up intervals. RPE cells exposed to IFCG and illumination had reduced viability relative to the negative control (cells exposed to saline), but not relative to those exposed to saline and illumination. Glial cells showed reduced viability at days 1 and 5, but not day 15. Illumination did not further reduce viability.

IFCG has been advocated as a safer macular vital stain than ICG. These results suggest that it is less likely to produce phototoxicity, but despite being nearly iso-osmolar, IFCG also produces damage in cultured glial cells.