Supercritical Development of Sustained Drug Delivery Intraocular Lenses

Controlled drug delivery systems (DDS) are receiving an increasing interest since they enhance the drug efficacy by a target action in the body and a sustained release profile. Most of these DDS are polymer based where the polymer is biocompatible and sometimes biodegradable and acts as a reservoir or a matrix for the drug. Supercritical technologies have been demonstrated to be a clean and effective alternative to traditional methods of drug and polymer processing. Recent developments are focusing on the elaboration of DDS. For that purpose, classical supercritical processes of particle generation (RESS, SAS, PGSS, ...) can be applied to form polymer/drug capsules or coprecipitates. Supercritical fluids can also be used as an impregnation vehicle of the drug within the polymeric matrix. The present work deals with supercritical impregnation of intraocular lenses (IOLs) to prevent postoperative endophthalmitis in cataract surgery. Commercially available rigid IOLs made from derivative of Poly (Methyl MethAcrylate) (PMMA) were impregnated with cefuroxime sodium, an antibiotic, and dexamethasone, an anti-inflammatory drug, through a discontinuous process. The impregnation efficacy was determined in term of impregnation yield as well as in term of in-vitro drug release. The influence of some experimental operating conditions was studied by varying the pressure (8 and 20 MPa), the temperature (308 and 333 K), or by adding a cosolvent (ethanol). The influence of the IOLs dioptre was also studied (+21.0 D, +30.0 D). At rapid depressurization rates, a non desired foaming phenomenon was observed in most of the experimental conditions. This phenomenon was avoided by carrying out slow depressurizations (0.2 MPa/min).