Neutral red assay of the cytotoxicity of fluorocarbon-coated polymethylmethacrylate intraocular lenses in vitro.

Polymethylmethacrylate (PMMA) intraocular lenses (IOLs) were coated with Teflon AF, an amorphous, transparent Teflon, to render them highly hydrophobic. Teflon-coated PMMA IOLs were immersed in culture medium for 30 days at 37 degrees C. Four concentrations of the IOL leachables, 2 concentrations of a toxic control (phenol), and complete liquid culture medium (nontoxic control) were incubated for 24 h in a 96-well plate containing confluent L-929 fibroblasts. The cytotoxic effect of each solution on the fibroblasts was quantitatively assessed by measuring the uptake of neutral red by the viable cells. After the extraction of the neutral red using 1% acetic acid-50% ethanol, the optical densities were measured with a microplate reader at 550 nm. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the surfaces of the IOLs. Only the optical densities in the wells containing fibroblasts that had been in contact with the phenol solutions were significantly lower than those in the wells incubated with the nontoxic control solution (p < 0.01). There were no signs of surface alteration by SEM, apart from some crystals on the IOLs. The crystals were composed of Na and Cl, as demonstrated by XPS. Aqueous extractables from the Teflon-coated IOLs produced no cytotoxic effects in the neutral red assay used.