(73e) Supercritical Solvent Impregnation for Drug-Loaded Lenses Using Carbon Dioxide With Water

Soft contact lens (SCL) has been expected as an alternative drug delivery system in order to solve the problem the low bioavailability in the case of eye drops. It is found that the impregnation of SCL with drug in aqueous solution results in the low amount of drug and burst-type drug release profile. The impregnation using supercritical carbon dioxid, supercritical solvent impregnation method (SSI) has been proposed as the alternative method in this work. The effect of the amount of water dissolving in supercritical carbon dioxideon the performance of the drug release profile from SCLs were studied. Salicylic acid was used as a drug impregnating into SCLs. The preparation of the SCLs with drug by SSI method were carried out at the constant temperature and pressure, 313 K and 11.0 MPa, and the depressurization rate of 0.1 MPa per minute.. The amount of water added into supercritical carbon dioxide was from 0 to 2.18 ml L^-1. (The saturated solubility of water in supercritical CO₂ is 1.19 ml L^-1). The Drug-loaded SCLs were soaked in the phosphate buffer solution at 310 K for the measurement of the released drug amount from SCLs. The concentrations of salicylic acid in the buffer solution were measured by an ultraviolet spectrometer. The performances of the drug-loaded SCLs were evaluated by the release profile and the amount of the drug. The SCLs processed in SSI without water present the burst-type drug release profile and the small amount of the drug. On the other hand, the SCLs processed with water present the sustained-type drug release profiles. In this case, the amount of water is larger than those in the case without water. The drug amount increases with increasing of water amount in supercritical carbon dioxide.