Browsing by Author "Antunes, Bernardo Paiva"
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- A bi-layer electrospun nanofiber membrane for plasmid DNA recovery from fermentation brothsPublication . Correia, Tiago R.; Antunes, Bernardo Paiva; Castilho, Pedro Henrique Barata; Nunes, José; Amorim, Maria T. Pessoa de; Escobar, Isabel; Queiroz, João; Correia, I.J.; Morão, AntónioThe demanding ever-increasing quantities of highly purified biomolecules by bio-industries, has triggered the development of new, more efficient, purification techniques. The application of membrane-based technologies has become very attractive in this field, for their high throughput capability, simplicity of operation and scale-up. Herein we report the production of a bi-layer membrane by electrospinning (ES), in which a support of poly ε-caprolactone nanofibers was coated with a polyethylene oxide/sodium alginate layer, and subsequently cross-linked with calcium chloride. The membranes were characterized by SEM, ATR-FTIR, contact angle measurements, and were applied in the recovery process of a plasmid. The results show that membranes retained the suspended solids while allowing the permeation of plasmid DNA, with high recovery yields and improved RNA retention. Moreover, they also showed a very low fouling tendency. To the best of our knowledge it is the first time that ES membranes are applied in this type of bioprocess.
- Chitosan/arginine–chitosan polymer blends for assembly of nanofibrous membranes for wound regenerationPublication . Antunes, Bernardo Paiva; Moreira, André; Gaspar, Vítor Manuel Abreu; Correia, Ilídio Joaquim SobreiraFrequently, skin is subjected to damaging events, such as deep cuts, burns or ulcers, which may compromise the integrity of this organ. To overcome such lesions, different strategies have been employed. Among them, wound dressings aimed to re-establish skin native properties and decreased patient pain have been pursued for a long time. Herein, an electrospun membrane comprised by deacetylated/arginine modified chitosan (CH-A) was produced to be used as a wound dressing. The obtained results showed that the membrane has a highly hydrophilic and porous three-dimensional nanofibrous network similar to that found in human native extracellular matrix. In vitro data indicate that human fibroblasts adhere and proliferate in contact with membranes, thus corroborating their biocompatibility. This nanofiber-based biomaterial also demonstrated bactericidal activity for two bacterial strains. In vivo application of CH-A nanofibers in full thickness wounds resulted in an improved tissue regeneration and faster wound closure, when compared to non-modified membranes. Such findings support the suitability of using this membrane as a wound dressing in a near future.
- Functionalization of polydimethylsiloxane membranes to be used in the production of voice prosthesesPublication . Ferreira, Paula; Carvalho, Álvaro; Correia, Tiago R.; Antunes, Bernardo Paiva; Correia, Ilídio Joaquim Sobreira; Alves, PatríciaThe voice is produced by the vibration of vocal cords which are located in the larynx. Therefore, one of the major consequences for patients subjected to laryngectomy is losing their voice. In these cases, a synthetic one-way valve set (voice prosthesis) can be implanted in order to allow restoration of speech. Most voice prostheses are produced with silicone-based materials such as polydimethylsiloxane (PDMS). This material has excellent properties, such as optical transparency, chemical and biological inertness, non-toxicity, permeability to gases and excellent mechanical resistance that are fundamental for its application in the biomedical field. However, PDMS is very hydrophobic and this property causes protein adsorption which is followed by microbial adhesion and biofilm formation. To overcome these problems, surface modification of materials has been proposed in this study. A commercial silicone elastomer, SylgardTM 184 was used to prepare membranes whose surface was modified by grafting 2-hydroxyethylmethacrylate and methacrylic acid by low-pressure plasma treatment. The hydrophilicity, hydrophobic recovery and surface energy of the produced materials were determined. Furthermore, the cytotoxicity and antibacterial activity of the materials were also assessed. The results obtained revealed that the PDMS surface modification performed did not affect the material's biocompatibility, but decreased their hydrophobic character and bacterial adhesion and growth on its surface.
- Microencapsulated chitosan–dextran sulfate nanoparticles for controled delivery of bioactive molecules and cells in bone regenerationPublication . Valente, Joana; Gaspar, Vítor Manuel Abreu; Antunes, Bernardo Paiva; Coutinho, Paula Isabel Teixeira Gonçalves; Correia, Ilídio Joaquim SobreiraThis research work aimed to synthesize and characterize a novel dual delivery system comprised of BSA-loaded in chitosan–dextran sulfate nanoparticulated carriers and mesenchymal stem cells that are encapsulated into alginate microparticles. The physicochemical and biological characteristics of this novel system, such as, morphology, release, swelling, and cytotoxicity were thoroughly characterized. The results obtained from confocal microscopy demonstrate that chitosan–dextran sulfate nanoparticles and cells are fully encapsulated within alginate microparticles, and spatially dispersed in the microparticle matrix. Moreover, scanning electron microscopy images revealed that these micro-sized carriers possess a rough surface, an important parameter that also promoted proper cell migration and adhesion. Notably, the incorporation of BSA in this duplex nano-micro delivery system extended its release profile throughout time, in comparison with microparticles alone, whilst not eliciting any cell damage. Taken together, these findings suggest that this dual carrier is a versatile delivery system with potential for a spatiotemporally controlled release of bioactive molecules and cells.
- Production of nanofiber-based membranes for biomolecule recoveryPublication . Antunes, Bernardo Paiva; Correia, Ilídio Joaquim SobreiraThe demanding of ever-increasing quantities of highly purified biomolecules by bioindustries has triggered the development of new, more efficient, purification techniques. The application of membrane-based technologies has become very attractive in this field, for their high throughput capability, simplicity of operation and scale-up. In this thesis it is reported the production of a bi-layer membrane by electrospinning (ES), in which a support of poly ε-caprolactone nanofibers was coated with a polyethylene oxide/sodium alginate layer, and subsequently cross-linked with calcium chloride. The membranes were characterized by SEM, ATR-FTIR, contact angle measurements, and then were applied in the recovery process of a plasmid. The results obtained show that membranes retained the suspended solids while allowing the permeation of plasmid DNA, with high recovery yields and improved RNA retention. Moreover, they also showed a very low fouling tendency.
- 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.