Percorrer por autor "Galante, Raquel"
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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."
- About the sterilization of chitosan hydrogel nanoparticlesPublication . Galante, Raquel; Rediguieri, Carolina F.; Kikuchi, Irene Satiko; Vasquez, Pablo A. S.; Colaço, Rogério; Serro, Ana Paula; Pinto, Terezinha J. A.In the last years, nanostructured biomaterials have raised a great interest as platforms for delivery of drugs, genes, imaging agents and for tissue engineering applications. In particular, hydrogel nanoparticles (HNP) associate the distinctive features of hydrogels (high water uptake capacity, biocompatibility) with the advantages of being possible to tailor its physicochemical properties at nano-scale to increase solubility, immunocompatibility and cellular uptake. In order to be safe, HNP for biomedical applications, such as injectable or ophthalmic formulations, must be sterile. Literature is very scarce with respect to sterilization effects on nanostructured systems, and even more in what concerns HNP. This work aims to evaluate the effect and effectiveness of different sterilization methods on chitosan (CS) hydrogel nanoparticles. In addition to conventional methods (steam autoclave and gamma irradiation), a recent ozone-based method of sterilization was also tested. A model chitosan-tripolyphosphate (TPP) hydrogel nanoparticles (CS-HNP), with a broad spectrum of possible applications was produced and sterilized in the absence and in the presence of protective sugars (glucose and mannitol). Properties like size, zeta potential, absorbance, morphology, chemical structure and cytotoxicity were evaluated. It was found that the CS-HNP degrade by autoclaving and that sugars have no protective effect. Concerning gamma irradiation, the formation of agglomerates was observed, compromising the suspension stability. However, the nanoparticles resistance increases considerably in the presence of the sugars. Ozone sterilization did not lead to significant physical adverse effects, however, slight toxicity signs were observed, contrarily to gamma irradiation where no detectable changes on cells were found. Ozonation in the presence of sugars avoided cytotoxicity. Nevertheless, some chemical alterations were observed in the nanoparticles.
- Chitosan nanogels for biomedical applications: choosing a suitable sterilization methodPublication . Galante, Raquel; Satiko, Irene; Bou-Chacra, Nádia; Colaço, Rogério; Serro, Ana Paula; Pinto, Terezinha J. A.
- 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
- Effect of sterilization on drugs and lenses for ophthalmic applicationsPublication . Topete, Ana; Oliveira, Andreia; Galante, Raquel; Bozukova, Dimitriya; Saramago, Benilde; Serro, A. P.
- Suitability of Kahili ginger stem fibres for reinforcement/filler of polymeric matrix compositesPublication . Lourenço, Bruno; Serôdio, Rita M. N.; Ferro, Alberto; Marques, Ana C.; Serro, Ana P.; Galante, Raquel; Garcês, Antonio; Claudio, Ricardo; Figueiredo-Pina, Célio G.Kahili ginger (KG) is one of the world's most invasive species, whose proliferation can be controlled by mechanical thinning. The KG chips produced in that process can be used as reinforcement/filler in polymer matrix composites (PMC), adding value to this waste. The aim of this study is to evaluate the possibility of using fibres obtained from KG stem chips for PMC. The chemical composition, thermal stability, water absorption, hydrophilicity and tensile mechanical properties of the KG fibres were assessed, and the values obtained were compared with those reported in the literature for other natural fibres commonly used in the manufacture of PMC. The results showed that the fibres treated with alkali/silane are thermally stable up to 200 °C, have a contact angle of 70°, a water absorption of 24 %, a modulus of elasticity of 23±3 GPa and a tensile strength of 277±113 MPa. Overall, the results demonstrate the potential of KG as a reinforcement/filler material for PMC.