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- Novel Alginate/Aloe Vera Hydrogel Blends as Wound Dressings for the Treatment of Several Types of WoundsPublication . Pereira, Rúben F.; Mendes, Ausenda; Bártolo, Paulo J.Currently, there is a significant increase in the use of natural materials for biomedical applications, mainly due to their biocompatibility, biodegradability and similar properties to the constituents of natural tissues. In this work, hydrogel films composed of alginate and Aloe vera gel were prepared and characterized for application in the treatment of several types of wounds (e.g. exuding, painful and dry). The films were prepared through a two-step procedure encompassing the film formation by a solvent-casting method and an additional crosslinking step to improve their properties. The physical, morphological and water absorption properties were characterized by introducing several variations in the Aloe vera content. The in vitro degradation behaviour of the films was investigated in the presence of the enzyme alginate lyase for 2 weeks. Results showed that Aloe vera improves the water absorption and the in vitro degradation rate of the films. In conclusion, this study indicates that the alginate/Aloe vera hydrogel films can be potentially explored as wound dressing for the treatment of different wound types.
- Influence of the Rheological Behaviour in Electrospun PCL Nanofibres Production for Tissue Engineering ApplicationsPublication . Dias, Juliana R.; Antunes, Filipe E.; Bártolo, Paulo J.A strategy to obtain functional tissues engineering with desired biomechanical properties was used to develop scaffolds with morphologies mimicking the native environment to guide tissue regeneration. Nonwoven scaffolds, with fibre dimensions at a nanometre scale, can mimic the physical structure of natural extracellular matrices (ECM). Though its clinical application is yet limited, nano/micro fibrous scaffolds produced by electrospinning gains more and more interest in different Tissue Engineering fields. The electrospinning technique is controlled by several parameters, such as polymer solution and processing ambient, being one of the most important parameters the solution viscosity, which allows defining the minimum viscosity needed to obtain fibres. This research work investigates the rheological behaviour of PCL solutions to produce nanoscale fibre meshes for cartilage application. Poly (ε-caprolactone) (PCL) solutions were prepared using glacial acetic acid (AA) and glacial acetic acid with triethylamine (AA/TEA) at different concentrations. It was necessary to double the value of the critical concentration (c*), that is 10 wt% for PCL/AA and 9,6wt% for PCL/AA/TEA, to prepare suitable fibres. Results also show that a more homogenous mesh can be produced by adding TEA.
- Mechanical and Biological Behaviour of PCL and PCL/PLA Scaffolds for Tissue Engineering ApplicationsPublication . Patrício, Tatiana; Glória, António; Bártolo, PauloA new biomanufacturing system allowing to produce three-dimensional matrices (scaffolds) with well defined internal geometries, uniform pore distribution and good adhesion among different adjacent layers. Polymers selected are Poly ε-caprolactone (PCL) and Poly Lactic Acid (PLA), both these polymers are used in medical applications. These two polymers are interesting biomaterials because they are complementary on their physical properties and biodegradability. This work aims to assess the temperature evaluation during the extrusion process and the influences of the temperatures on the PCL and PCL/PLA scaffolds with lay down pattern 90º and pore size 350μm. The results demonstrated that extrusion process not modified the thermal properties of the scaffolds and these structures are able to sustain MG-63cells.
- Characterisation of PCL and PCL/PLA Scaffolds for Tissue EngineeringPublication . Patrício, T.; Domingos, M.; A. Gloria; Bártolo, P.This paper investigates the use of PCL and PCL/PLA scaffolds produced using a novel additive biomanufacturing system called BioCell Printing. PCL/PLA blends were prepared using melt blend and solvent casting techniques. Scaffolds with 0/90° architecture and 350 μm of pore size were morphologically evaluated using scanning electron microscopy and atomic force microscopy. Biological tests, using osteosarcoma cell line G-63, were performed using the Alamar Blue Assay and Alkaline Phosphatase Activity. Results show that the BioCell Printing system produces scaffolds with regular and reproducible architecture, presenting no toxicity and enhancing cell attachment and proliferation. It was also possible to observe that the addition of PLA to PCL scaffolds strongly improves the biomechanical performance of the constructs.
- Alginate/Aloe Vera Hydrogel Films for Biomedical ApplicationsPublication . Pereira, Rúben F.; Mendes, Ausenda; Bártolo, PauloThis paper describes a methodology to produce hydrogel films, composed of alginate and Aloe vera, for wound healing and drug delivery applications. The films were prepared through the solvent-casting method and subsequently submitted to an additional cross-linking step to improve their properties. Alginate films with different Aloe vera contents (5, 15 and 25%) were prepared and its properties evaluated in terms of thickness, transparency, swelling behavior and in vitro degradation. Results show a positive influence of Aloe vera on the transparency of the films, in both dry and wet state. Films were immersed in acetate buffer at pH 5.5 simulating the value of the skin, to evaluate its water absorption capacity. It was found that water absorption increases as the Aloe vera content increases, suggesting that Aloe vera enhances the hydrophilic properties of the films. The in vitro degradation tests were performed through the incubation of the films, for 10 weeks, in a simulated body fluid at 37°C. After this period, films kept its structure integrity exhibiting a weight loss in the range of 14.1-18.6%.
- Morphological Characteristics of Electrospun PCL Meshes – The Influence of Solvent Type and ConcentrationPublication . Dias, J.; Bártolo, P.Fibrous scaffolds, with fiber dimensions on the nanometer scale, are ideal for tissue engineering applications as they can mimic the physical structure of natural extracellular matrix. This paper investigates the effect of the solvent type and the solvent concentration on the morphological and hydrophobic characteristics of Polycaprolactone (PCL) meshes. Acetone and acetic acid with triethylamine (TEA) were used as solvents with different concentrations of PCL. Results show that its use allows the formation of meshes with high surface roughness, less surface friction and less hydrophobicity.
- Cranial Biomechanical SimulationPublication . Perestrelo, Pedro; Bártolo, Paulo; Paranhos, Maurício; Noritomi, Pedro; Silva, JorgeIn order to improve the understanding, detection and prevention of traumatic brain injury (TBI), a step forward must be taken in the research. A pursue of biomechanical and clinical theories in separate, must give place to a joined effort. Therefore, it is proposed the development of a virtual platform using BioCAD protocol, surface modeling software and finite element method (FEM) analysis software, in order to achieve a model that can be adapted to the needs of the user or patient. This will result in an innovative and most needed tool, so that research and prevention of TBI enter a new level.
- Ink Removal on Plastic Films Printed by FlexographyPublication . Bozzola, Fernando; Nascimento, Bruna Guilherme do; Vasco, Joel C.; Silva, Nelson; Lagoa, Fernando; Capela, Carlos; Heleno, Lizete; Gaspar, Marcelo; Oliveira, Nelson S.Plastics are key engineering materials for our society and economy, mainly due to their multifunctionality and ease of processing. Nonetheless, their main drawback is related to the fact that when these cannot be reprocessed, they do generate waste, which leads to several environmental impacts. Therefore, considering plastics’ circularity, minimizing their waste, and the resulting impacts, stresses the need for these to be recyclable. One of the main challenges that concern their recyclability is the deinking of plastic films when printed by flexography. The current technology uses non-bio-based surfactants and non-renewable surfactants, which are harmful to the environment. Therefore, the main objective of current research is to develop an environmentally sustainable process for ink removal on printed post-industrial flexible plastic films using bio-based surfactants. This process focuses on obtaining a deinked plastic that may be reprinted, avoiding this way for inappropriate disposal or reprocessing problems. The value increase of upcycling such post-industrial waste makes it possible to match the quality of the virgin plastic, which is key to carrying out an effective cost analysis of recycled plastic when compared to the new plastic films. Dedicated laboratory deinking procedures were undertaken with transparent polyethylene films printed by flexography with different conditions. Preliminary results show the dedicated experimental ink removal procedure using bio-based surfactants to be effective and environmentally sustainable.
- Feasibility Study of the PET Fines Incorporation into Recycling ProcessesPublication . Nascimento, Bruna Guilherme do; Bozzola, Fernando; Vasco, Joel C.; Parnigoni, Milena; Capela, Carlos; Heleno, Lizete; Gaspar, Marcelo; Oliveira, Nelson S.Circular economy principles focus on the need to preserve natural resources and foster the use of environmentally sustainable practices. Concerning the use of plastics in a circular economy, increasingly demanding solutions have to be developed towards the zero-waste goal sought after by researchers and society alike. Particular attention has been put into the recycling of PET, mainly due to its wide spectrum of use and, consequently, to large volumes of related waste. The PET mechanical recycling process requires these waste materials to be shredded into PET flakes. Following such a procedure, these flakes are pelletized to be used again as feedstock. Considering the main stages of the mechanical recycling processes, which include plastic screening, shredding and washing, significant amounts of end waste materials are generated. This end-waste integrates small scale particles that are designated by plastic fines. Concerning the PET recycling process, the PET fines resulting from its mechanical recycling are not currently valued due to several technical issues, such as their high contamination level and the complexity of sorting them from other small-size particles. Current research focuses on the feasibility of incorporating these PET fines into the film/injection extruders, avoiding this way the need for an intermediate pelletization stage. To allow for such direct incorporation of PET fines into recycling processes, different decontamination and sorting solutions were implemented and tested. The current study is based on analyzing the mechanical properties of PET fines, using laboratory tests such as FTIR, DSC, MFI, moisture content, tensile tests and bending tests. Preliminary results allow foreseeing the successful direct incorporation of PET fines into PET recycling.
- Thermal Stability of PCL/PLA Blends Produced by Physical Blending ProcessPublication . Patrício, Tatiana; Bártolo, PauloThe poly ɛ-caprolactone (PCL) and poly lactid acid (PLA) were used for prepared blends with different percentage. PCL/PLA blends (70/30 wt% and 50/50 wt%) were prepared by physical blending process, called solvent casting. These blends were analysed by morphological, thermal and rheological tests in order to evaluate the miscibility and thermal stability of the polymers and their blends, important characteristics to apply in scaffold fabrication. The Simultaneous Thermal Analyser (STA) demonstrated two separated melting peaks in the blends, which show the immiscible polymers. The blends surface were analysed through Scanning Electron Microscope (SEM) and the results shows the presence of droplets in the blends surface, characteristic of an immiscible polymer. The results of rheological measurements present a good thermal stability of the polymers and their blends.