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- Drug delivery systems : a brief approachPublication . Franco, Margarida Cabrita
- Controlled in Vitro Release of Levodopa from Sodium Alginate MembranesPublication . Franco, Margarida; Biscaia, Sara; Viana, Tânia; Alves, Nuno; Morouço, PedroLevodopa (LD) plays a central role in Parkinson’s Disease therapeutics. In this study, we aimed to encapsulate LD in sodium alginate (SA) membranes, and to study its dissolution profiles. Two types of SA membranes, loaded with two different amounts of LD were prepared and compared (M1: 85 mg per 50 ml SA/LD; M2: 127.5 mg per 75 ml SA/LD); membranes production followed a solvent-casting methodology. Calcium chloride was used as a crosslinking agent. LD solubility tests were performed to predict sink conditions required for complete drug dissolution. LD dissolution assays were carried out and UV spectrophotometry was used for cumulative release percentage determination. The obtained data were mathematically evaluated and fitted into mathematical dependent models; the difference factor (f1), the similarity factor (f2) and other parameters like dissolution efficiency (DE) were also used. No differences in the dissolution profiles of both membranes were noticed. Thus, increasing the amount of LD, but keeping the same concentration, led to a similar controlled release. The membranes presented in this work are expected to be a promising contribution in the development of a new controlled drug delivery system for LD administration.
- A Novel Biomanufacturing System to Produce Multi-Material Scaffolds for Tissue Engineering: Concept and Preliminary ResultsPublication . Viana, T.; Biscaia, S.; Dabrowska, E.; Franco, M.; Carreira, P.; Morouço, P.; Alves, N.This research work aims to validate a new system that enables the fabrication of multimaterial 3D structures using poly(e-caprolactone) and sodium alginate for potential use in Tissue Engineering applications. To produce multi-material scaffolds for Tissue Engineering, accurate techniques are needed to obtain three-dimensional constructs with clinically appropriate size and structural integrity. This paper presents a novel biomanufacturing system which can fabricate 3D scaffolds with precise shape and porosity, through the control of all fabrication modules by an integrated computational platform. The incorporation of a clean flow unit and a camera makes it possible to produce scaffolds in a clean environment and provides a monitoring tool to analyse constructs during the production, respectively.
- Additive manufactured stoneware fired in microwave furnacePublication . Santos, Tiago; Ramani, Melinda; Devesa, Susana; Batista, Catarina; Franco, Margarida; Duarte, Isabel; Costa, Luís; Ferreira, Nelson; Alves, Nuno; Pascoal-Faria, PaulaAdditive manufacturing (AM) techniques have revolutionized the concept of building parts not only in laboratory contexts but also in industry environments and can be applied to distinct fields such as the health, automotive and aeronautics sectors [...]
- 3D-printed teeth in endodontics: Why, how, problems and future: A narrative reviewPublication . Reis, Tiago; Barbosa, Cláudia; Franco, Margarida; Baptista, Catarina; Alves, Nuno; Castelo-Baz, Pablo; Martín-Cruces, José; Martin-Biedma, BenjaminThree-dimensional printing offers possibilities for the development of new models in endodontics. Numerous studies have used 3D-printed teeth; however, protocols for the standardization of studies still need to be developed. Another problem with 3D-printed teeth is the different areas of literature requested to understand the processes. This review aims to gather evidence about 3Dprinted teeth on the following aspects: (1) why they are advantageous; (2) how they are manufactured; (3) problems they present; and (4) future research topics. Natural teeth are still the standard practice in ex vivo studies and pre-clinical courses, but they have several drawbacks. Printed teeth may overcome all limitations of natural teeth. Printing technology relies on 3D data and post-processing tools to form a 3D model, ultimately generating a prototype using 3D printers. The major concerns with 3D-printed teeth are the resin hardness and printing accuracy of the canal anatomy. Guidance is presented for future studies to solve the problems of 3D-printed teeth and develop well-established protocols, for the standardization of methods to be achieved. In the future, 3D-printed teeth have the possibility to become the gold standard in ex vivo studies and endodontic training.
- 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.
- The Use of Polypropylene and High-Density Polyethylene on Cork Plastic Composites for Large Scale 3D PrintingPublication . Brites, Fernando; Malça, Cândida; Gaspar, F.; Horta, J. F.; Franco, M. C.; Biscaia, S.; Mateus, A.This work focuses on studying the possibility of 3D printing of composite materials composed by cork and a polymer matrix (CPC). Initially the cork was mixed with two types of polymers (HDPE and PP) in different proportions and later processed using extrusion and injection. The composites were tested to study the physical, chemical and mechanical properties. The material was then tested on a large-scale 3D printer to study its feasibility and the ability to produce new products through 3D printing. Attention was focused on the use of pure cork, varying the concentration of cork and coupling agent in thermoplastic matrix composites of PP and HDPE. It was demonstrated that the increase of 5wt.% of coupling agent in the two types of polymers significantly improved the mechanical properties and adhesion between the phases but the increase in cork concentration decreased mechanical properties and crystallinity. The CPCs with PP showed to have better mechanical properties, better aesthetic and internal structural quality, and easier processability than those with HDPE matrix. Nevertheless, the HDPE CPCs showed a high degree of crystallization. Concerning 3D printing, it was demonstrated the possibility of making new products based on natural cork fibers, showing promising results, although additional research is still needed to optimize the process.
- Fit accuracy of removable partial denture metal frameworks produced by CAD-CAM – a clinical studyPublication . Conceição, Pedro R.; Franco, Margarida Cabrita; Alves, Nuno; Portugal, Jaime; Neves, Cristina B.Objectives: To assess the effect of a CAD-CAM protocol fabrication on the clinical fit accuracy of removable partial denture metal frameworks to abutment teeth. Methods: Fifteen patients with partial edentulism were selected to participate in this clinical study, and twenty dental arch rehabilitations were planned. For each dental arch (n=20), two cobalt-chromium frameworks were produced through two protocols: CAD-CAM production (experimental group); and conventional lost-wax casting technique (control group). Clinical fit accuracy was assessed using an indirect quantitative method to evaluate the gap between the framework occlusal rest and the corresponding rest seat. A silicone mold of that gap was obtained, digitized, and analyzed by micro-computed tomography. The two silicone molds obtained for each occlusal rest were overlapped and evaluated for thickness and volume. Data were analyzed with the paired t test for silicone thickness results and the Wilcoxon test for silicone volume results (α= 0.05). Results: Considering the two dependent variables under study, no statistically significant (p=0.441 for silicone thickness and p=0.204 for silicone volume) differences were found between groups. Conclusions: The results of this study suggest that the CAD-CAM protocol applied is a viable method for the production of removable partial denture metal frameworks.
- Evaluation of Root Canal Filling with a Bioceramic Sealer Using Micro-Computed Tomography: A Pilot StudyPublication . Vasconcelos, Isabel; Pereira, Mário Rito; Ginjeira, António; Franco, Margarida; Morouço, Pedro; Alves, NunoThis pilot study aims to define a protocol for optimizing the micro-computed tomography (micro-CT) settings to evaluate in the future research the root canal filling in oval shaped canals. Thirty distal canals of mandibular molars were used. After preparation of the canals, the roots were randomly divided into five groups. The canals were filled with two types of sealers (Endosequence BC Sealer or AH Plus) and two types of gutta percha (Protaper Next cones and Endosequence BC cones), using thermal obturation in comparison with a single cone obturation technique. Each specimen was scanned three times using a micro-CT device at a resolution of 30,1 μm. The first scan was done for selecting the specimen according the inclusion criteria, the second one postinstrumentation and the last micro-CT scan after obturation the specimens. For the present study, the images were only evaluated with qualitative criteria and the settings for acquisition, reconstruction and analysis of micro-CT images were tested.
- 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.