J. of Supercritical Fluids 52 (2010) 306–316 Contents lists available at ScienceDirect The Journal of Supercritical Fluids journal homepage: www.elsevier.com/locate/supflu Development of therapeutic contact lenses using a supercritical solvent impregnation method Viviana P. Costa a , Mara E.M. Braga a , Joana P. Guerra a , Ana R.C. Duarte b , Catarina M.M. Duarte b , Eugénio O.B. Leite c , Maria H. Gil a , Hermínio C. de Sousa a,∗ a CIEPQPF, Chemical Engineering Department, University of Coimbra, Rua Sílvio Lima, Pólo II, 3030-790 Coimbra, Portugal b Nutraceuticals and Controlled Delivery, ITQB/IBET, Aptd. 12, 2781-901 Oeiras, Portugal c Faculty of Health Sciences, University of Beira Interior, Rua Marquês D’Ávila e Bolama, 6201-001 Covilhã, Portugal article info Article history: Received 11 August 2009 Received in revised form 28 January 2010 Accepted 1 February 2010 Keywords: Therapeutic contact lenses Drug delivery systems Supercritical solvent impregnation abstract We present some selected results indicating the feasibility of preparing therapeutic finished ophthalmic articles, namely commercially available soft contact lenses, using a supercritical solvent impregnation (SSI) technique. Several commercial soft contact lenses were tested and, among these, four lenses were selected for more complete studies: Nelfilcon A (FocusDailies ® , CIBA Vision), Omafilcon A (Proclear ® Compatibles, CooperVision), Methafilcon A (Frequency ® 55, CooperVision) and Hilafilcon B (SofLens ® 59 Comfort, Bausch & Lomb). Supercritical carbon dioxide (scCO 2 ) was the chosen supercritical fluid and two ophthalmic drugs were tested: flurbiprofen (a NSAID, hydrophobic) and timolol maleate (an anti-glaucoma drug, hydrophilic). The effects of operational pressure, of impregnation duration and of the addition of a cosolvent (ethanol) were studied on the overall drug loading yields. Depending on the experiment, we employed pressures from 9 up to 16 MPa and impregnation times from 30 up to 180 min. Temperature was kept constant and equal to 313 K. The employed depressurization rates were kept low and between 0.1 and 0.2 MPa/min. Results are discussed in terms of the employed operational conditions and taking in consideration all the possible interactions between supercritical fluids, drugs, cosolvents and the polymers which com- pose the employed hydrogel contact lenses. In vitro drug release experiments were carried out in order to evaluate the resulting drug release profiles. Obtained results were also compared with drug-loaded contact lenses obtained by conventional drug “soaking” in aqueous solutions. Results also proved that SSI can be considered as a viable, efficient and safe alternative for the impregnation of drugs, includ- ing those of hydrophobic character or presenting low aqueous solubility, into commercial soft contact lenses. SSI proved to be a “tunable” process since the variation of the employed operational conditions indicated that it is possible to control the amount of impregnated drug. In the end, the ophthalmic articles were recovered undamaged and without the presence of harmful solvent residues. This method also per- mits to process already prepared commercial contact lenses, without interfering with their manufacture methods and, after processing, store them for future use. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Presently, several ophthalmic diseases and conditions are affect- ing the quality of life of hundreds of millions of people all over the world. Cataracts, age-related macular degeneration (AMD), dia- betic retinopathy and glaucoma are very common pathologies and are increasing worldwide [1,2]. In fact, and as our population ages, these eye diseases are becoming more prevalent and causing a major impact on the quality of life for most ageing people [1–4]. Although presently there are several therapeutic approaches for ∗ Corresponding author. Tel.: +351 239 798749; fax: +351 239 798703. E-mail address: hsousa@eq.uc.pt (H.C. de Sousa). treating many of these ocular diseases, there are still some great challenges as well as opportunities in ocular therapeutics to dis- cover and to develop better therapeutic procedures that will treat or control a greater number of ophthalmic diseases and conditions [2,5] and, potentially, even other non-ophthalmic pathologies [5,6]. Usually, a medication is applied to the surface of the eye for two main purposes: to treat the outside of the eye (e.g., for infec- tions) or to provide intraocular treatment through the cornea (e.g., for glaucoma). There are many potential routes for local and con- trolled delivery of bioactive and therapeutic molecules to the eye [6–11] but the most common dosage form in ocular treatment still is topical ocular eye drops [12]. However, topical drug deliv- ery can be limited by a number of effective removal mechanisms, like blinking, high tear fluid turnover and nasolacrimal drainage, 0896-8446/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.supflu.2010.02.001