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- Characterization of Biocompatible Poly(Ethylene Glycol)-Dimethacrylate Hydrogels for Tissue EngineeringPublication . Lopes, João; Fonseca, Rita; Viana, Tânia; Fernandes, Cristiana; Morouço, Pedro; Moura, Carla; Biscaia, SaraTissue Engineering depends on broadly techniques to regenerate tissues and/or organ functions. To do so, tailored polymeric and/or hydrogel scaffolds may be used to ensure the appropriate regeneration. Hydrogels are suitable materials for constructing cell-laden matrices as they can be produced with incorporation of cells and rapidly cross-linked in situ through photopolymerisation reactions. Measurement of the polymerization degree, as well as resistance to compression and water retention are fundamental tests to evaluate the characteristics of hydrogels. In this work, free-radical polymerisation of poly(ethylene glycol)-dimethacrylate (PEGDMA) in UV light was assessed. Several hydrogels with different photoinitiator and water contents were produced to evaluate their influence on hydrogels behaviour. Experiments showed that variations on water and photoinitiator content induce changes in the physical and chemical behaviour of hydrogels. As it was found, water content prevents polymerisation to occur and reduces the mechanical properties of hydrogels weakening them. Furthermore, differences were found in varying water content from 15 to 30%, since this increase turned hydrogels more fragile and increase their stabilization time for water retention.
- Organismos geneticamente modificados, qual o limite?Publication . Fonseca, Ana RitaEste trabalho resulta de uma pesquisa bibliográfica, reflectindo desta forma a preocupação da autora sobre um assunto que poderá afectar a Europa, no decorrer da aprovação do tratado trasntlântico TTIP.
- Traffic Vertical Signposting: Materials Characterization and Structural Numerical SimulationPublication . Franco, M.; Fonseca, R.; Gomes, S.; Biscaia, S.; Brites, F.; Pascoal-Faria, P.; Mateus, A.The existing metallic solutions used for vertical traffic signs are associated with higher costs and environmental issues due to their manufacturing and degradation, when compared with polymeric solutions. Thus, the development of vertical signs considering the injection from polymeric materials in order to overcome problems related with sustainability, maintenance costs, and to achieve higher resistance to corrosion assumes nowadays an important role. The use of ecofriendly and innovative products considering the industrial waste combined with synthetic polymers performing the appropriate mechanical properties, can also be studied to find out new solutions that allow to solve the aforementioned problems. Additionally, these innovative vertical signs can contribute to avoid vandalism events related with theft and graffiti activities. This work presents the prior materials investigation and the structural design of vertical signs that are intended to be produced through polymer injection. Three main steps were considered: i) materials research, ii) materials characterisation through the analysis of polycarbonate resin isolated and in different sets of mixtures with different concentrations through tensile testing and static water contact angle measurements to find the optimal material composition; and iii) structural numerical simulation considering polycarbonate resin and using the current standard EN 12899-1 [1] to compute wind resistance, temporary and permanent deflections. Both experimental and numerical results led to an optimized proposal of the vertical signposting structural design.
- Micro Computed Tomography Detects Changes in Liver Density in Control and in Prediabetes RatsPublication . Fonseca, A. R.; Franco, M. C.; Sacramento, J.; Melo, B.; Conde, S.V.; Guarino, M. P.Fatty liver disease is an early event in the development of insulin resistance that predicts the presence and progression of the metabolic syndrome. In humans, fatty liver diagnosis is usually performed by imaging techniques based on ultrasound, computed tomography and magnetic resonance. Rodent models are often used in metabolic research allowing access to tissue biopsies however, studies describing ex vivo computed tomography of biological samples are scarce. X-ray Micro Computed Tomography (Micro-CT) is an imaging technique that reveals the internal structure of materials in great detail, also allowing a quantitative analysis of properties such as density measured as arbitrary Hounsfield Units (HU). Herein, we tested the hypothesis that Micro CT detects changes in liver tomographic density induced by metabolic diseases and its reversal upon therapeutic surgical intervention. Two groups of male Wistar rats were used: a group submitted to a hypercaloric diet for 14 weeks to induce prediabetes and the control group submitted to a standard diet). The animals were randomly submitted to a surgical treatment and maintained on their respective diets after the procedure for 11 more weeks. Liver and adipose tissues samples were excised and samples were scanned using a compact X-ray micro-CT scanner. The projection images obtained were analyzed and reconstructed and values of HU density were calculated after calibration for all samples. Results showed that liver density was lower in prediabetes rats (74.8±5.87 HU) than in control animals (97.2±6.3 HU), p<0.05. Liver density was not affected by surgical treatment in control animals however, in prediabetes animals, the surgical therapy restored liver density to control values. Visceral fat density was significantly lower than hepatic density, as expected and was affected, neither by the disease condition nor by the surgical treatment. We concluded that micro-CT detects metabolic disease-induced changes in liver density, but not in visceral adipose tissue density in biopsy samples ex vivo. Changes in hepatic density, assessed by micro-CT, correlate with disease state and with therapeutic interventions.