Osmolarity and spectrophotometric property of brilliant blue green define the degree of toxicity on retinal pigment epithelial cells exposed to surgical endoilluminator

OBJECTIVE To evaluate the effect of varying concentrations of brilliant blue green (BBG) and their different biochemical characteristics on retinal pigment epithelial (RPE) cells under xenon light source illumination at varying distances to identify safe parameters for intraoperative use. METHODS Human retinal RPE cells (ARPE-19) were exposed to two concentrations (0.25 and 0.50 mg/mL) of BBG and illuminated with a xenon surgical illuminator at varying distances (10 and 25 mm), intensity levels, and time intervals (1, 5, and 15 minutes). Additionally, the effect of osmolarity was examined by diluting BBG in different concentrations of glucose. Cytotoxicity of BBG and osmolarity effects on cell viability were evaluated using a WST-1 assay. Light absorption and emission characteristic of BBG in different solvents were measured using a plate reader at different wavelengths. Lastly, the activity of caspase-3 was also studied. RESULTS Cell viability of ARPE-19 cells was 77.4%±12.7%, 78.7%±17.0%, and 65.0%±19.7% at 1, 5, and 15 minutes to exposure of high illumination xenon light at 10 mm (P<0.05) compared to controls. At both distances of illumination (10 and 25 mm), similar cell viabilities were seen between 1 and 5 minutes of exposure. However, there was a decline in viability when the illumination was carried out to 15 minutes in all groups (P<0.05). There was no significant reduction in cell viability in presence or absence of xenon light in different osmolar solutions concentrations of glucose (P>0.05). Maximal light absorption of BBG was noted between 540 and 680 nm. Activated caspase-3 level was not significant in both the concentrations of BBG (P>0.05). CONCLUSION Our findings suggest that BBG at 0.25 mg/mL during vitreoretinal surgery is safe and not toxic to RPE cells up to 5 minutes under focal high illumination (10 mm) and up to 15 minutes under medium diffuse illumination (25 mm). BBG was safe to be mixed with isotonic glucose solution at the concentration range of 2.5%-10%, regardless of the illumination status.