Journal of Supercritical Fluids, Vol.131, 11-18, 2018
Loading of vitamin E into silicone hydrogel by supercritical carbon dioxide impregnation toward controlled release of timolol maleate
Supercritical CO2 impregnation was applied to loading of vitamin E into silicone hydrogel for development of controlled release system of timolol maleate, hydrophilic ocular drug for glaucoma. Vitamin E was loaded into the silicone hydrogel to reduce the diffusivity of timolol maleate. Supercritical impregnation accomplishes the large amount of loaded vitamin E into the silicone hydrogel at the low concentration in supercritical CO2 compared with that by ethanol liquid solution. The loading of vitamin E 0.49 g g(-1)-hydrogel by the supercritical impregnation results in the significant reduction of the diffusivity of timolol maleate in the silicone hydrogel to 1.4 x 10(-5) mm(2) min(-1) much smaller than of that without vitamin E, 13 x 10(-5) mm(2) min(-1). The release system of timolol maleate in silicone hydrogel with the low diffusivity is obtained from the effective loading of vitamin into the silicone hydrogel using the supercritical impregnation.