Browsing by Author "Paradiso, Patrizia"
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- About the effect of eye blinking on drug release from pHEMA-based hydrogels: an in vitro studyPublication . Galante, Raquel; Paradiso, Patrizia; Moutinho, Maria Guilhermina; Fernandes, Ana Isabel; Mata, José; Matos, António; Colaço, Rogério; Saramago, Benilde; Serro, Ana Paula"The development of new ophthalmic drug delivery systems capable of increasing the residence time of drugs in the eye and improve its bioavailability relatively to eyedrops has been object of intense research in recent years. Several studies have shown that drug loaded therapeutic soft contact lenses (SCLs) constitute a promising approach, with several potential advantages as compared with collyria. The main objective of this work is to study the effect of repetitive load and friction cycles caused by the eye blinking, on the drug release from hydrogels used in SCLs which, as far as we know, was never investigated before. Two poly-2-hydroxyethylmethacrylate based hydrogels, pHEMA-T and pHEMA-UV, were used as model materials. Levofloxaxin was chosen as model drug. The hydrogels were fully characterized in what concerns structural and physicochemical properties. PHEMA-UV revealed some superficial porosity and a lower short range order than PHEMA-T. We observe that the load and friction cycles enhanced the drug release from pHEMAUV hydrogels. The application of a simple mathematical model, which takes into account the drug dilution caused by the tear flow, showed that the enhancement of the drug release caused by blinking on this hydrogel may be relevant in in vivo conditions. Conversely, the more sustained drug release from pHEMA-T is not affected by load and friction cycles. The conclusion is that, depending on the physicochemical and microstructural characteristics of the hydrogels, blinking is a factor that may affect the amount of drug delivered to the eye by SCLs and should thus be considered."
- Controlled drug delivery from ophthalmic lensesPublication . Topete, Ana; Oliveira, Andreia; Pimenta, Andreia; Silva, Diana; Carrilho, Magda; Paradiso, Patrizia; Kumar, Prashneel; Galante, Raquel; Mata, José; Colaço, Rogério; Saramago, Benilde; Serro, Ana Paula
- Controlled release of antibiotics from vitamin E–loaded silicone-hydrogel contact lensesPublication . Paradiso, Patrizia; Serro, Ana Paula; Saramago, Benilde; Colaço, Rogério; Chauhan, AnujSymptoms of bacterial and fungal keratitis are typically treated through the frequent application of antibiotic and antifungal eye drops. The high frequency of half hourly or hourly eye drop administration required to treat these indications is tedious and could reduce compliance. Here, we combine in vitro experiments with a mathematical model to develop therapeutic soft contact lenses to cure keratitis by extended release of suitable drugs. We specifically focus on increasing the release duration of levofloxacin and chlorhexidine from 1-DAY ACUVUE® TrueEye™ and ACUVUE OASYS® contact lenses by incorporating vitamin E diffusion barriers. Results show that 20% of vitamin E loading in the contact lens increases the release duration of levofloxacin to 100 h and 50 h from 1-DAY ACUVUE® TrueEye™ and ACUVUE OASYS®, respectively, which is a 3- and 6-fold increase, respectively, for the 2 lenses. For chlorhexidine, the increase is 2.5- and 10-fold, for the TrueEye™ and OASYS®, respectively, to 130 h and 170 h. The mass of drug loaded in the lenses can be controlled to achieve a daily release comparable to the commonly prescribed eye drop therapy. The vitamin E–loaded lenses retain all critical properties for in vivo use.
- Diffusion-based design of multi-layered ophthalmic lenses for controlled drug releasePublication . Pimenta, Andreia F. R.; Serro, Ana Paula; Paradiso, Patrizia; Saramago, Benilde; Colaço, RogérioThe study of ocular drug delivery systems has been one of the most covered topics in drug delivery research. One potential drug carrier solution is the use of materials that are already commercially available in ophthalmic lenses for the correction of refractive errors. In this study, we present a diffusion-based mathematical model in which the parameters can be adjusted based on experimental results obtained under controlled conditions. The model allows for the design of multi-layered therapeutic ophthalmic lenses for controlled drug delivery. We show that the proper combination of materials with adequate drug diffusion coefficients, thicknesses and interfacial transport characteristics allows for the control of the delivery of drugs from multi-layered ophthalmic lenses, such that drug bursts can be minimized, and the release time can be maximized. As far as we know, this combination of a mathematical modelling approach with experimental validation of non-constant activity source lamellar structures, made of layers of different materials, accounting for the interface resistance to the drug diffusion, is a novel approach to the design of drug loaded multi-layered contact lenses.