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- Improved osteoblast cell affinity on plasma-modified 3-D extruded PCL scaffoldsPublication . Domingos, M.; Intranuovo, F.; Gloria, A.; Gristina, R.; Ambrosio, L.; Bártolo, P. J.; Favia, P.Cellular adhesion and proliferation inside three-dimensional synthetic scaffolds represent a major challenge in tissue engineering. Besides the surface chemistry of the polymers, it is well recognized that scaffold internal architecture, namely pore size/shape and interconnectivity, has a strong effect on the biological response of cells. This study reports for the first time how polycaprolactone (PCL) scaffolds with controlled micro-architecture can be effectively produced via bioextrusion and used to enhance the penetration of plasma deposited species. Low-pressure nitrogen-based coatings were employed to augment cell adhesion and proliferation without altering the mechanical properties of the structures. X-ray photoelectron spectroscopy carried out on different sections of the scaffolds indicates a uniform distribution of nitrogen-containing groups throughout the entire porous structure. In vitro biological assays confirm that plasma deposition sensitively promotes the activity of Saos-2 osteoblast cells, leading to a homogeneous colonization of the PCL scaffolds.
- Influence of Aloe vera on water absorption and enzymatic in vitro degradation of alginate hydrogel filmsPublication . Pereira, Rúben F.; Carvalho, Anabela; Gil, M.H.; Mendes, Ausenda; Bártolo, Paulo J.This study investigates the influence of Aloe vera on water absorption and the in vitro degradation rate of Aloe vera-Ca-alginate hydrogel films, for wound healing and drug delivery applications. The influence of A. vera content (5%, 15% and 25%, v/v) on water absorption was evaluated by the incubation of the films into a 0.1 M HCl solution (pH 1.0), acetate buffer (pH 5.5) and simulated body fluid solution (pH 7.4) during 24 h. Results show that the water absorption is significantly higher for films containing high A. vera contents (15% and 25%), while no significant differences are observed between the alginate neat film and the film with 5% of A. vera. The in vitro enzymatic degradation tests indicate that an increase in the A. vera content significantly enhances the degradation rate of the films. Control films, incubated in a simulated body fluid solution without enzymes, are resistant to the hydrolytic degradation, exhibiting reduced weight loss and maintaining its structural integrity. Results also show that the water absorption and the in vitro degradation rate of the films can be tailored by changing the A. vera content.
- Body composition, strength static and isokinetic, and bone health: comparative study between active adults and amateur soccer playersPublication . Óscar M. Tavares; João P. Duarte; André O. Werneck; Daniela C. Costa; Paulo Sousa-e-Silva; Diogo Martinho; Leonardo G. O. Luz; Morouço, Pedro; João Valente-dos-Santos; Rui Soles-Gonçalves; Jorge Conde; José M. Casanova; Manuel J. Coelho-e-SilvaObjective: To compare tissue composition, total and regional bone mineral content and bone mineral density, static hand grip and knee joint isokinetic strength between amateur soccer players and Control Group. Methods: Cross-sectional study. Air displacement plethysmography was used to estimate body volume and, in turn, density. Body composition, bone mineral content and bone mineral density were assessed for the whole body and at standardized regions using dual energy X-ray absorptiometry. Static grip strength was assessed with an adjustable dynamometer, and peak torque derived from isokinetic strength dynamometer (concentric muscular knee actions at 60°/s). Magnitude of the differences between groups was examined using d-Cohen. Results: Compared to healthy active adults, soccer players showed larger values of whole body bone mineral content (+651g; d=1.60; p<0.01). In addition, differences between groups were large for whole body bone mineral density (d=1.20 to 1.90; p<0.01): lumbar spine, i.e. L1-L4 (+19.4%), upper limbs (+8.6%) and lower limbs (+16.8%). Soccer players attained larger mean values in strength test given by static hand grip protocol (+5.6kg, d=0.99; p<0.01). Conclusion: Soccer adequately regulates body composition and is associated better bone health parameters (bone mineral content and density at whole-body and at particular sites exposed to mechanical loadings).
- Semidirect products and crossed modules in monoids with operationsPublication . Martins-Ferreira, Nelson; Montoli, Andrea; Sobral, ManuelaWe describe actions, semidirect products and crossed modules in categories of monoids with operations. Moreover we characterize, in this context, the internal categories corresponding to crossed modules. Concrete examples in the cases of monoids, semirings and distributive lattices are given.
- Fabrication of channeled scaffolds with ordered array of micro-pores through microsphere leaching and indirect Rapid Prototyping techniquePublication . Tan, J. Y.; Chua, Chee Kai; Leong, K. F.Advanced scaffold fabrication techniques such as Rapid Prototyping (RP) are generally recognized to be advantageous over conventional fabrication methods in terms architectural control and reproducibility. Yet, most RP techniques tend to suffer from resolution limitations which result in scaffolds with uncontrollable, random-size pores and low porosity, albeit having interconnected channels which is characteristically present in most RP scaffolds. With the increasing number of studies demonstrating the profound influences of scaffold pore architecture on cell behavior and overall tissue growth, a scaffold fabrication method with sufficient architectural control becomes imperative. The present study demonstrates the use of RP fabrication techniques to create scaffolds having interconnected channels as well as controllable micro-size pores. Adopted from the concepts of porogen leaching and indirect RP techniques, the proposed fabrication method uses monodisperse microspheres to create an ordered, hexagonal closed packed (HCP) array of micro-pores that surrounds the existing channels of the RP scaffold. The pore structure of the scaffold is shaped using a single sacrificial construct which comprises the microspheres and a dissolvable RP mold that were sintered together. As such, the size of pores as well as the channel configuration of the scaffold can be tailored based on the design of the RP mold and the size of microspheres used. The fabrication method developed in this work can be a promising alternative way of preparing scaffolds with customized pore structures that may be required for specific studies concerning cell-scaffold interactions.
- An alternative method to produce metal/plastic hybrid components for orthopedics applicationsPublication . Silva, M.; Mateus, A.; Oliveira, D.; Malça, C.The demand for additive processes that provide components with high technological performance became overriding regardless of the application area. For medical applications, the orthopedics field—multimaterial orthoses and splints—can clearly benefit from direct additive manufacturing using a hybrid process instead of the traditional handmade manufacturing, which is slow, expensive, inaccurate, and difficult to reproduce. The ability to provide faster better orthoses, using innovative services and technologies, resulting in lower recovery times, reduced symptoms, and improved functional capacity, result in a significant impact on quality of life and the well-being of citizens. With these purposes, this work presents an integrate methodology, that includes the tridimensional (3D) scanning, 3D computer-aided design modeling, and the direct digital manufacturing of multimaterial orthoses and splints. Nevertheless, additive manufacturing of components with functional gradients, multimaterial components, e.g. metal/plastic is a great challenge since the processing factors for each one of them are very different. This paper proposes the addition of two advanced additive manufacturing technologies, the selective laser melting and the stereolithography, enabling the production of a photopolymerization of the polymer in the voids of a 3D metal mesh previously produced by selective laser melting. Based on biomimetic structures concept, this mesh is subject to a previous design optimization procedure in order to optimize its geometry, minimizing the mass involved and evidencing increased mechanical strength among other characteristics. A prototype of a hybrid additive manufacturing device was developed and its flexibility of construction, geometrical freedom, and different materials processability is demonstrated through the case study—arm orthosis—presented in this work.
- Multi-material NiTi-PEEK hybrid cellular structures by Selective Laser Melting and Hot Pressing: Tribological characterizationPublication . Costa, M. M.; Bartolomeu, F.; Palmeiro, J.; Guimarães, B.; Alves, N.; Miranda, G.; Silva, F. S.In this study, a multi-material NiTi-PEEK cellular structured solution was designed, produced and characterized targeting orthopedic applications. For that purpose, Selective Laser Melting (SLM) technique was used to produce NiTi cellular structures with different open-cell sizes and wall thicknesses. Hot Pressing (HP) technique was used to introduce PEEK in the open-cells of NiTi structures to obtain multi-material components. Morphological characterization showed that the selected SLM processing parameters were suited to achieve high-quality parts without significant defects. Tribological characterization proved an enhanced wear resistance to the multi-material specimens when compared with the mono-material NiTi structures. These multi-material structures are a promising solution for providing a customized stiffness and superior wear resistance to NiTi structures to be integrated in innovative orthopedic designs.
- A comparison of 3D poly(ε-caprolactone) tissue engineering scaffolds produced with conventional and additive manufacturing techniques by means of quantitative analysis of SR μ-CT imagesPublication . Brun, F; Intranuovo, F; Mohammadi, S; Domingos, M.; Favia, P; Tromba, GThe technique used to produce a 3D tissue engineering (TE) scaffold is of fundamental importance in order to guarantee its proper morphological characteristics. An accurate assessment of the resulting structural properties is therefore crucial in order to evaluate the effectiveness of the produced scaffold. Synchrotron radiation (SR) computed microtomography (μ-CT) combined with further image analysis seems to be one of the most effective techniques to this aim. However, a quantitative assessment of the morphological parameters directly from the reconstructed images is a non trivial task. This study considers two different poly(ε-caprolactone) (PCL) scaffolds fabricated with a conventional technique (Solvent Casting Particulate Leaching, SCPL) and an additive manufacturing (AM) technique (BioCell Printing), respectively. With the first technique it is possible to produce scaffolds with random, non-regular, rounded pore geometry. The AM technique instead is able to produce scaffolds with square-shaped interconnected pores of regular dimension. Therefore, the final morphology of the AM scaffolds can be predicted and the resulting model can be used for the validation of the applied imaging and image analysis protocols. It is here reported a SR μ-CT image analysis approach that is able to effectively and accurately reveal the differences in the pore- and throat-size distributions as well as connectivity of both AM and SCPL scaffolds.
- EditorialPublication . Bártolo, Paulo; Chua, C.K.Additive manufacturing (AM) technologies play a key role in the advancement of biomedical applications. In this issue, we share with the readers the roles of AM technologies in two applications for biomedical engineering, namely scaffolds for tissue engineering and a composite model for club foot.
- Additive manufacturing techniques for scaffold-based cartilage tissue engineeringPublication . Caseiro, Ana Rita; Almeida, Henrique A.; Bártolo, Paulo J.Articular cartilage damage is of great concern as it creates chronic pain and reduction of joint movement, leading to osteoarthritis. In current treatments, the resulting healing tissues lack structural organisation of cartilage and consequently have inferior mechanical properties when compared to native cartilage, therefore being prone to failure. Tissue engineering has long worked on cartilage regeneration and several requirements have been identified for the engineered structures to meet the desired function, by combining biodegradable and biocompatible materials, cells and growth factors, aiming at the production of biological structures closely resembling the native tissue.Within the scaffold based techniques for cartilage tissue production, conventional methods have shown limitations, especially regarding the control over the microstructure and repeatability of the produced constructs. Therefore, additive manufacturing techniques grew popular, allowing for a high level of control over the internal scaffold architecture and external shape of the construct, as well as guaranteeing its reproducibility.