Clyde L Schultz1, Douglas W Morck. 1. DirectContact LLC, Boston, Massachusetts, USA. schultzc@ucalgary.ca <schultzc@ucalgary.ca>
Abstract
BACKGROUND: This work was conducted to investigate the uptake and release of epidermal growth factor (EGF) from hydrogel contact lenses and to determine whether the released protein would be therapeutically active in a rabbit corneal epithelial defect model of ocular trauma, prior to use in humans. METHODS: The uptake and release of EGF from hydrogel contact lens materials were determined by high-pressure liquid chromatography. Contact lenses composed of vasurfilcon A or lotrafilcon A (containing silicone) were incubated in a source solution containing 0.4 ppm EGF for seven hours. To determine the kinetics of drug uptake into the contact lens matrix, drug concentration in the source solution was measured at zero, one, 60, 240 and 420 minutes. To determine the kinetics of release, loaded contact lenses were immersed in a recipient solution of phosphate-buffered saline. Therapeutic activity in vivo was investigated by placing prepared lenses on the surface of abraded corneas of New Zealand White rabbits, with abraded corneas of contralateral eyes used as controls. Control eyes were treated with contact lenses placed in saline for injection. Wound closure was assessed hourly. RESULTS: Uptake and release of EGF were demonstrated for vasurfilcon A but not lotrafilcon A contact lens materials. The retention time of EGF released from vasurfilcon A contact lenses was similar to control EGF not exposed to contact lens polymers. The greatest adsorption of EGF into the lens material occurred within approximately 120 minutes, with a flattening of the rate of uptake thereafter. Abraded eyes in rabbits showed a significantly higher overall healing rate for EGF-treated contact lenses compared with control eyes (p < 0.0001). CONCLUSIONS: EGF can be delivered from some but not all hydrogel materials. Lens materials composed of silicone may not be useful for delivering EGF to the eye. EGF-treated contact lenses may be a useful device to facilitate healing of ocular wounds.
BACKGROUND: This work was conducted to investigate the uptake and release of epidermal growth factor (EGF) from hydrogel contact lenses and to determine whether the released protein would be therapeutically active in a rabbit corneal epithelial defect model of ocular trauma, prior to use in humans. METHODS: The uptake and release of EGF from hydrogel contact lens materials were determined by high-pressure liquid chromatography. Contact lenses composed of vasurfilcon A or lotrafilcon A (containing silicone) were incubated in a source solution containing 0.4 ppm EGF for seven hours. To determine the kinetics of drug uptake into the contact lens matrix, drug concentration in the source solution was measured at zero, one, 60, 240 and 420 minutes. To determine the kinetics of release, loaded contact lenses were immersed in a recipient solution of phosphate-buffered saline. Therapeutic activity in vivo was investigated by placing prepared lenses on the surface of abraded corneas of New Zealand White rabbits, with abraded corneas of contralateral eyes used as controls. Control eyes were treated with contact lenses placed in saline for injection. Wound closure was assessed hourly. RESULTS: Uptake and release of EGF were demonstrated for vasurfilcon A but not lotrafilcon A contact lens materials. The retention time of EGF released from vasurfilcon A contact lenses was similar to control EGF not exposed to contact lens polymers. The greatest adsorption of EGF into the lens material occurred within approximately 120 minutes, with a flattening of the rate of uptake thereafter. Abraded eyes in rabbits showed a significantly higher overall healing rate for EGF-treated contact lenses compared with control eyes (p < 0.0001). CONCLUSIONS:EGF can be delivered from some but not all hydrogel materials. Lens materials composed of silicone may not be useful for delivering EGF to the eye. EGF-treated contact lenses may be a useful device to facilitate healing of ocular wounds.