Dye Solutions Based on Lutein and Zeaxanthin: In Vitro and In Vivo Analysis of Ocular Toxicity Profiles

Purpose: To study the safety profile of Lutein/Zeaxanthin(L/Z)-based natural dye solutions in in vitro and in vivo models. Material and methods: In vitro cytotoxicity and cellular growth experiments were carried out on ARPE-19 and human corneal epithelial (HCE) cell lines using different L/Z-based dye solutions, either alone or in association with brilliant blue (BB) or trypan blue (TB). Light and transmission electron microscopy studies were performed seven days after intravitreal injection of dye solutions in rabbits. Electroretinogram (ERG) recordings were taken at baseline and before histopathology. Results: In vitro cytotoxicity assays demonstrated that the different L/Z-based solutions (from 0.3 to 2%), either alone or in association with BB (0.025%) or TB (0.04%), did not significantly alter mitochondrial activity (<= 15%) in the cell lines tested. In addition, in vitro cell growth was inhibited by up to 60% depending on the dye solution, and in direct proportion to the concentration assayed. There was no evidence of structural alterations in the neurosensory retina, retinal pigment epithelium (RPE), or choriocapillaris-choroidal complex. b-Wave ERG records showed no significant differences (+/- 15.2%) in comparison with baseline. Conclusions: L/Z-based dye solutions demonstrated a safe profile in in vitro and in vivo models, and may be a useful tool for staining intraocular structures.