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- Corrosion behaviour of PEEK or β-TCP-impregnated Ti6Al4V SLM structures targeting biomedical applicationsPublication . Costa, M.M.; Dantas, T.A.; Bartolomeu, F.; Alves, N.; Silva, F.S.; Miranda, G.; Toptan, F.Ti6Al4V cellular structures were produced by selective laser melting (SLM) and then filled either with beta-tricalcium phosphate (β-TCP) or PEEK (poly-ether-ether-ketone) through powder metallurgy techniques, to improve osteoconductivity and wear resistance. The corrosion behavior of these structures was explored considering its importance for the long-term performance of implants. Results revealed that the incorporation of open cellular pores induced higher electrochemical kinetics when being compared with dense structures. The impregnation of β-TCP and PEEK led to the creation of voids or gaps between the metallic matrix and the impregnated material which also influenced the corrosion behavior of the cellular structures.
- Advanced face mask filters based on PCL electrospun meshes dopped with antimicrobial MgO and CuO nanoparticlesPublication . Ferreira, Carolina A. M.; Guerreiro, Sara F.C.; Valente, Joana F. A.; Patrício, Tatiana M.F.; Alves, Nuno; Mateus, Artur; Dias, Juliana R.The pandemic situation caused by coronavirus clearly demonstrated the need for alternatives able to protect the respiratory tract and inactivate the infectious agents. Based on this, antibacterial face-mask filters of polycaprolactone (PCL) dopped with magnesium oxide (MgO) and copper oxide (CuO) nanoparticles (NPs) were produced using an electrospinning technique. A morphological analysis of electrospun meshes evaluated the success of nanoparticles’ incorporation as well as the average fibers’ diameters (481 +- 272 nm). The performance of electrospun nanofibers was also assessed in terms of tensile strength (0.88 +- 0.25 MPa), water vapor permeability (11,178.66 +- 35.78 g.m-2.day-1), stability under wet conditions and antibacterial activity according to the standard guidelines. The filters showed structural stability up to 2 h of washing and improved antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) for optimized concentrations of MgO and CuO NPs. Overall, electrospun meshes with antibacterial activity were successfully developed for advanced filtering applications.
- Comprehensive review on full bone regeneration through 3D printing approachesPublication . Fernandes, Cristiana; Moura, Carla; Ascenso, Rita M.T.; Amado, Sandra; Alves, Nuno; Pascoal-Faria, PaulaOver the last decades, the number of work accidents associated with bone fractures has increased leading to a growing concern worldwide. Currently, autografts, allografts, and xenografts are used for bone regeneration. However, their application has associated risks. Tissue engineering (TE) has brought solutions to address these problems, through the production of temporary supports, providing mechanical support to the formation of new bone tissue and biocompatible and biodegradable scaffolds, which allow cell adhesion and proliferation to ensure bone formation. The combination of materials and structure with the technique to be used will directly influence their physical and chemical properties and, consequently, their action in contributing to bone regeneration. Thus, the focus of this chapter is to perform an exhaustive literature review and a critical analysis of the state of the art in bone TE and present a proposal of an optimized temporary support geometry for bone regeneration in case of large bone defects. For this, it was listed and identified the best choice of biomaterials, fabrication method, cell type and their culture conditions (static vs. dynamic), and/or the inclusion of growth factors for the repair of large bone defects.
- Sheep Gait Biomechanics and the Assessment of Musculoskeletal Conditions: A Systematic ReviewPublication . Silva, Rui; Dimas, Ivo Santos; Fernandez, Justin W.; Alves, Nuno; Morouço, Pedro; Maurício, Ana Colette; Veloso, António; Sandra, AmadoIn recent years, sheep have been reported as the ideal animal model to study osteoporosis, hence it is important to identify instruments, tools and ideal parameters needed to assess the effects of different treatments. In previous studies conducted in other animal models with osteoporosis, the most common parameters used for evaluation concerned primarily bone properties, such as the dual X-ray absorptiometry. However, biomechanical gait analysis as an integrative functional parameter and a non-invasive method, will be an important tool in research and clinical applications. This research review was performed using the PubMed database and included studies related to sheep with outcome measures concerning functional performance assessed during gait in vivo; and excluded studies related with cardiovascular disease and sperm properties, which include other animal species, with outcomes not related with functional locomotor evaluation. Only studies related with bone properties were analyzed. The most frequent and relevant included parameters were the following: mean peak vertical ground force reaction, gait cycle and stance/swing phase duration, percentage of stance/swing phase in a gait cycle, stride length and the stifle joint angles during a gait cycle. Gait biomechanical parameters have been established for the assessment of some clinical orthopedic condition using sheep models but not currently for osteoporosis.
- Continuous production of highly tuned silk/calcium-based composites: exploring new pathways for skin regenerationPublication . Veiga, Anabela; Magalhaes, Rui; Duarte, Marta M.; Dias, Juliana R.; Alves, Nuno M.; Costa-Pinto, Ana Rita; Castro, Filipa; Rocha, Fernando; Oliveira, Ana L.Calcium plays an important role in barrier function repair and skin homeostasis. In particular, calcium phosphates (CaPs) are well established materials for biomedical engineering due to their biocompatibility. To generate biomaterials with a more complete set of biological properties, previously discarded silk sericin (SS) has been recovered and used as a template to grow CaPs. Crucial characteristics for skin applications, such as antibacterial activity, can be further enhanced by doping CaPs with cerium (Ce) ions. The effectiveness of cell attachment and growth on the materials highly depends on their morphology, particle size distribution, and chemical composition. These characteristics can be tailored through the application of oscillatory flow technology, which provides precise mixing control of the reaction medium. Thus, in the present work, CaP/SS and CaP/SS/Ce particles were fabricated for the first time using a modular oscillatory flow plate reactor (MOFPR) in a continuous mode. Furthermore, the biological behavior of both these composites and of previously produced pure CaPs was assessed using human dermal fibroblasts (HDFs). It was demonstrated that both CaP based with plate-shaped nanoparticles and CaP-SS-based composites significantly improved cell viability and proliferation over time. The results obtained represent a first step towards the reinvention of CaPs for skin engineering.
- Experimental validation of a computational fluid dynamics model using micro-particle image velocimetry of the irrigation flow in confluent canalsPublication . Pereira, Mário Rito; Silva, Gonçalo; Semião, Viriato; Silvério, Vânia; Martins, Jorge N.R.; Pascoal-Faria, Paula; Alves, Nuno; Dias, Juliana R.; Ginjeira, AntónioAim: This study aimed to experimentally validate a computational fluid dynamics (CFD) model, using micro-particle image velocimetry (micro-PIV) measurements of the irrigation flow velocity field developed in confluent canals during irrigation with a side-vented needle. Methodology: A microchip with confluent canals, manufactured in polydimethylsiloxane was used in a micro-PIV analysis of the irrigation flow using a side-vented needle placed 3 mm from the end of the confluence of the canals. Velocity fields and profiles were recorded for flow rates of 0.017 and 0.1 ml/s and compared with those predicted in CFD numerical simulations (using a finite volume commercial code –FLUENT) for both laminar and turbulent regimes. Results: The overall flow pattern, isovelocity and vector maps as well as velocity profiles showed a close agreement between the micro-PIV experimental and CFD predicted data. No relevant differences were observed between the results obtained with the laminar and turbulent flow models used. Conclusions: Results showed that the laminar CFD modelling is reliable to predict the flow in similar domains.
- A Computer Tool for 3D Shape Recovery of FruitsPublication . Gaspar, Miguel; Pascoal-Faria, Paula; Amado, Sandra; Alves, NunoCharacterizing a fruit’s mechanical behavior is an important step towards reducing economic losses due to bruising. Several 3D scanning technologies allow to obtain the external geometry of a fruit, but no easily accessible tools exist for the acquisition of the geometry of internal structures such as the core. We propose a low-cost destructive method for tomographic reconstruction of a fruit from scanned slices. A method for overcoming the difficulties in registering the different images is also presented.
- Ti6Al4V-PEEK multi-material structures – design, fabrication and tribological characterization focused on orthopedic implantsPublication . Bartolomeu, F.; Abreu, C.S.; Moura, C.G.; Costa, M.M.; Alves, N.; Silva, F.S.; Miranda, G.A multi-material concept that gathers Ti6Al4V and PEEK properties in a cellular structured component was designed, fabricated and investigated targeting hip implants. SLM and pressure assisted injection techniques were used to obtain Ti6Al4V-PEEK multi-material structures. Aiming to reproduce to some extension the tribological phenomena occurring during and after hip implant insertion, five tribological tests were outlined and performed. The obtained results showed that the presence of PEEK on the Ti6Al4V-PEEK cellular structures led to a substantial improvement on the wear resistance (62% reduction in the mass loss) when compared to the material currently available on market for hip implants. The multi-material solution here investigated shows a good compromise between the primary stability after implant insertion and the wear performance.
- A biorefinery approach to the biomass of the seaweed Undaria pinnatifida (Harvey Suringar, 1873): obtaining phlorotannins-enriched extracts for wound healingPublication . Ferreira, Carolina A. M.; Félix, Rafael; Félix, Carina; Januário, Adriana P.; Alves, Nuno; Novais, Sara C.; Dias, Juliana R.; Lemos, Marco F.L.Brown seaweeds are recognized sources of compounds with a wide range of properties and applications. Within these compounds, phlorotannins are known to possess several bioactivities (e.g., antioxidant, anti-inflammatory, and antimicrobial) with potential to improve wound healing. To obtain phlorotannins enriched extracts from Undaria pinnatifida, a biorefinery was set using lowcost industry-friendly methodologies, such as sequential solid–liquid extraction and liquid–liquid extraction. The obtained extracts were screened for their antioxidant and antimicrobial activity against five common wound pathogens and for their anti-inflammatory potential. The ethanolic wash fraction (wE100) had the highest antioxidant activity (114.61 +- 10.04 mmol mg-1 extract by Diphenyl-1-picrylhydrazyl (DPPH) and 6.56 +-1.13mMeq. Fe II mg-1 extract by and Ferric Reducing Antioxidant Power (FRAP)), acting efficiently against Gram-negative (Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) bacteria, and showing a nitric oxide production inhibition over 47% when used at 0.01 ug mL-1. NMR and FTIR chemical characterization suggested that phlorotannins are present. Obtained fraction wE100 proved to be a promising candidate for further inclusion as wound healing agents, while the remaining fractions analyzed are potential sources for other biotechnological applications, giving emphasis to a biorefinery and circular economy framework to add value to this seaweed and the industry.
- Optimization of phycobiliprotein pigments extraction from red algae Gracilaria gracilis for substitution of synthetic food colorantsPublication . Pereira, Tatiana; Barroso, Sónia; Mendes, Susana; Amaral, Renata A.; Dias, Juliana R.; Baptista, Teresa; Saraiva, Jorge A.; Alves, Nuno; Gil, Maria M.The extraction of phycobiliprotein (PBP) pigments from red algae Gracilaria gracilis was optimized using maceration, ultrasound-assisted extraction (ultrasonic water bath and ultrasonic probe), high pressure-assisted extraction, and freeze-thaw. The experimental conditions, namely homogenization time (t1), buffer concentration (C), treatment time (t2), biomass: buffer ratio (R), and pressure (P), were optimized using Response Surface Methodology (RSM). The yield of phycoerythrin (PE) extracted, determined spectroscopically, was used as the response variable. Maceration was the most efficient extraction method yielding 3.6 mg PE/g biomass under the optimal conditions (t1 = t2 = 10 min; C = 0.1 M; R = 1:50). Scanning Electron Microscopy (SEM) analysis of the biomass before and after the cell disruption treatments revealed a more efficient cell wall rupture with maceration.