Utilization of in vitro methods to determine the biocompatibility of intraocular lens materials

In vitro methods for measuring the adhesion and viability of lens epithelial cells on implant devices are needed to assess material biocompatibility. We investigated whether the use of confocal microscopy and spectrophotometric methods could determine the viability and adhesion of cells on a silicone biomaterial. Human lens epithelial cells adhered to silicone were treated with 0.01% benzalkonium chloride (cationic surfactant), 0.1% sodium dodecyl sulfate (anionic surfactant), and 10% Tween 20 (nonionic surfactant). Cell viability was then assessed using two fluorescent dyes (calcein and ethidium homodimer-1). Adhesion was determined directly by measuring the number of attached cells after surfactant treatment and by an indirect method that utilized the colorimetric agent crystal violet. The number of viable cells remaining on the biomaterial was determined both immediately after exposure and after the cells were allowed to grow for 1 day following surfactant exposure. The measurements for adhesion showed that the anionic surfactant weakened cell surface binding more than the cationic or nonionic surfactant. This study demonstrated that confocal microscopy in conjunction with crystal violet as an indirect colorimetric indicator can quantify the viability and adhesion of human lens epithelial cells attached to a material surface.