Browsing by Issue Date, starting with "2014-01-01"
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- Surface modification of polyurethane films by plasma and ultraviolet light to improve haemocompatibility for artificial heart valvesPublication . Alves, Patrícia; Cardoso, Rute; Correia, Tiago R.; Antunes, Bernardo Paiva; Correia, Ilídio Joaquim Sobreira; Ferreira, PaulaProsthetic cardiac valves implantation is a common procedure used to treat heart valve diseases. Although there are different prostheses already available in the market (either mechanical or bioprosthetic), their use presents several problems, specifically concerning thrombogenicity and structural failure. Recently, some progresses have been achieved in developing heart valves based on synthetic materials with special emphasis in polymers. Among them, polyurethanes are one of the most commonly used for the production of these devices. Herein, Elastollan®1180A50, a thermoplastic polyurethane (TPU), was used to formulate films whose surfaces were modified by grafting 2-hydroxyethylmethacrylate (HEMA) either by ultra-violet (UV) or by plasma treatment. All films were analyzed before and after grafting. X-ray photoelectron spectroscopy (XPS) measurements were used to evaluate TPU surfaces functionalization. HEMA grafting was confirmed by the increase of the hydroxyl (OH) groups’ concentration at the surface of the films. Atomic force microscopy (AFM) analysis was done to evaluate the surface topography of the biomaterials. Results showed that the roughness of the surface decreased when HEMA was grafted, especially for plasma treated samples. After grafting the films’ hydrophilicity was improved, as well as the polar component of the surface energy, by 15–30%. Hydrophobic recovery studies using milli Q water or PBS were also performed to characterize the stability of the modified surface, showing that the films maintained their surface properties along time. Furthermore, blood-contact tests were performed to evaluate haemolytic and thrombogenic potential. The results obtained for HEMA grafted surfaces, using plasma treatment, confirmed biomaterials biocompatibility and low thrombogenicity. Finally, the cytotoxicity and antibacterial activity of the materials was assessed through in vitro assays for both modified films. The obtained results showed enhanced bactericidal activity, especially for the films modified with plasma.
- Synthesis and characterization of micelles as carriers of non-steroidal anti-inflammatory drugs (NSAID) for application in breast cancer therapyPublication . Marques, João Filipe Gonçalves; Gaspar, Vítor Manuel Abreu; Costa, Elisabete C.; Paquete, Catarina; Correia, Ilídio Joaquim SobreiraNon-steroidal anti-inflammatory drugs (NSAIDS) are emerging as a particularly valuable class of drugs due to their recently reported anti-tumoral activity in colorectal cancer. However, despite this tremendous potential, their bioavailability at the tumor microenvironment remains rather limited. To overcome this issue, in this work we synthesized biocompatible micellar nanocarriers composed of amphiphilic chitosan to deliver ibuprofen into breast cancer cells and evaluate its anti-tumor activity, while avoiding side-effects. Our results reveal that the formulations produced herein self-assembly into spherical micelles with suitable sizes for tumor accumulation (108–252 nm). Furthermore, by using a vortex-sonication method, ibuprofen was successfully encapsulated with high efficiency. Cell uptake studies show that ibuprofen-loaded micelles are readily internalized by tumor cells and deliver their cargo in the intracellular compartment as demonstrated by confocal microscopy images. This fact led to a remarkable reduction in cancer cell viability (<13%), at a relatively low drug dosage, illustrating the anti-tumoral activity of ibuprofen when delivered to breast cancer cells. These findings demonstrate the promising potential of chitosan micelles as carriers of cost-effective NSAIDS for application in breast cancer therapy.