The intraocular staining potential of anthocyanins and their retinal biocompatibility: a preclinical study

Purpose: To perform preclinical studies to determine the efficacy and safety of anthocyanins as stains for the internal limiting membrane (ILM) of the eye. Materials and methods: Cyanidin (Cya), delphinidin (Del), luteolinidin (Lut), peonidin (Peo) and pelargonidin (Pel) were evaluated. These natural dyes were used to stain the lens capsule and ILM of pig eyes. The effects of these dyes on retinal cell viability was determined using a water-soluble tetrazolium salt assay, and oxidative stress was measured in vitro. Histopathology, in situ TUNEL labelling, transmission electronic microscopy (TEM), and electroretinography (ERG) were performed on rats following the intravitreal and subretinal injection of the neuroprotective dyes. Results: All anthocyanins stained the lens capsule and ILM of the pigs at a concentration of 1 mg/ml. Del, Lut and Peo were non-toxic and produced survival rates in the ARPE19 and RGC5 cells that were similar to those in control cells. We treated eyes with H₂O₂ and three dyes (Del, Lut, and Peo) to explore the possible neuroprotective effects and observed significantly higher survival rates in the ARPE19 cells treated with Del, Lut or Peo and the RGC5 cells treated with Lut or Peo than those in the control cells. Three dyes were intravitreally and subretinally injected into rats in vivo, and the histology showed mildly disorganized retinal cell layers. TUNEL staining and TEM examinations did not reveal additional toxic effects. Rat ERGs were not altered after intravitreal injections. Conclusions: This preclinical study, Del, Lut, and Peo show potential as staining agents and warrant further investigation as vital dyes.