Percorrer por autor "Bártolo, Paulo J."
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- 3D printing of new biobased unsaturated polyesters by microstereo-thermal-lithographyPublication . Gonçalves, Filipa A. M. M.; Costa, Cátia S. M. F.; Fabela, Inês G. P.; Farinha, Dina; Faneca, Henrique; Simões, Pedro N.; Serra, Arménio C.; Bártolo, Paulo J.; Coelho, Jorge F. J.New micro three-dimensional (3D) scaffolds using biobased unsaturated polyesters (UPs) were prepared by microstereo-thermal-lithography (μSTLG). This advanced processing technique offers indubitable advantages over traditional printing methods. The accuracy and roughness of the 3D structures were evaluated by scanning electron microscopy and infinite focus microscopy, revealing a suitable roughness for cell attachment. UPs were synthesized by bulk polycondensation between biobased aliphatic diacids (succinic, adipic and sebacic acid) and two different glycols (propylene glycol and diethylene glycol) using fumaric acid as the source of double bonds. The chemical structures of the new oligomers were confirmed by proton nuclear magnetic resonance spectra, attenuated total reflectance Fourier transform infrared spectroscopy and matrix assisted laser desorption/ionization-time of flight mass spectrometry. The thermal and mechanical properties of the UPs were evaluated to determine the influence of the diacid/glycol ratio and the type of diacid in the polyester's properties. In addition an extensive thermal characterization of the polyesters is reported. The data presented in this work opens the possibility for the use of biobased polyesters in additive manufacturing technologies as a route to prepare biodegradable tailor made scaffolds that have potential applications in a tissue engineering area.
- Additive manufacturing of tissues and organsPublication . Melchels, Ferry P.W.; Domingos, Marco; Klein, Travis J.; Malda, Jos; Bártolo, Paulo J.; Hutmacher, Dietmar W.Additive manufacturing techniques offer the potential to fabricate organized tissue constructs to repair or replace damaged or diseased human tissues and organs. Using these techniques, spatial variations of cells along multiple axes with high geometric complexity in combination with different biomaterials can be generated. The level of control offered by these computer-controlled technologies to design and fabricate tissues will accelerate our understanding of the governing factors of tissue formation and function. Moreover, it will provide a valuable tool to study the effect of anatomy on graft performance. In this review, we discuss the rationale for engineering tissues and organs by combining computer-aided design with additive manufacturing technologies that encompass the simultaneous deposition of cells and materials. Current strategies are presented, particularly with respect to limitations due to the lack of suitable polymers, and requirements to move the current concepts to practical application.
- 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.
- Cell-instructive pectin hydrogels crosslinked via thiol-norbornene photo-click chemistry for skin tissue engineeringPublication . Pereira, Rúben; Barrias, Cristina C.; Bártolo, Paulo J.; Granja, Pedro L.Cell-instructive hydrogels are attractive for skin repair and regeneration, serving as interactive matrices to promote cell adhesion, cell-driven remodeling and de novo deposition of extracellular matrix compo nents. This paper describes the synthesis and photocrosslinking of cell-instructive pectin hydrogels using cell-degradable peptide crosslinkers and integrin-specific adhesive ligands. Protease-degradable hydro gels obtained by photoinitiated thiol-norbornene click chemistry are rapidly formed in the presence of dermal fibroblasts, exhibit tunable properties and are capable of modulating the behavior of embedded cells, including the cell spreading, hydrogel contraction and secretion of matrix metalloproteases. Keratinocytes seeded on top of fibroblast-loaded hydrogels are able to adhere and form a compact and dense layer of epidermis, mimicking the architecture of the native skin. Thiol-ene photocrosslinkable pec tin hydrogels support the in vitro formation of full-thickness skin and are thus a highly promising plat form for skin tissue engineering applications, including wound healing and in vitro testing mod
- Combined Elastic and Shear Stress Solicitations for Topological Optimisation of Micro-CT Based ScaffoldsPublication . Almeida, Henrique A.; Bártolo, Paulo J.Advanced additive manufacturing technologies, namely Biomanufacturing, are being used to fabricate scaffolds with controlled architecture for tissue engineering applications. These technologies combined with computer-aided design (CAD) enable to produce three-dimensional structures layer-by-layer in a multitude of biomaterials. Actual prediction of the effective mechanical properties of scaffolds produced by Biomanufacturing, is very important for tissue engineering applications. A novel computer based technique for scaffold design is topological optimisation. Topological optimisation is a form of "shape" optimisation, usually referred to as "layout" optimisation. The goal of topological optimisation is to find the best use of material for a body that is subjected to either a single load or a multiple load distribution. In this research work, a topological optimization strategy is presented to find out the best material use for a construct subject to either a single load or a multiple load distribution, maximising its mechanical behaviour under tensile and shear stress solicitations. The proposed topological optimization scheme enables the design of ideal topological architectures based on existing biologic Micro-CT data for the design of biomimetic scaffolds.
- Electrospun polycaprolactone (PCL) degradation: An in vitro and in vivo studyPublication . Dias, Juliana R.; Sousa, Aureliana; Augusto, Ana; Bártolo, Paulo J.; Granja, Pedro L.Polycaprolactone (PCL) is widely used in tissue engineering due to its interesting properties, namely biocompatibility, biodegradability, elastic nature, availability, cost efficacy, and the approval of health authorities such as the American Food and Drug Administration (FDA). The PCL degradation rate is not the most adequate for specific applications such as skin regeneration due to the hydrophobic nature of bulk PCL. However, PCL electrospun fiber meshes, due to their low diameters resulting in high surface area, are expected to exhibit a fast degradation rate. In this work, in vitro and in vivo degradation studies were performed over 90 days to evaluate the potential of electrospun PCL as a wound dressing. Enzymatic and hydrolytic degradation studies in vitro, performed in a static medium, demonstrated the influence of lipase, which promoted a rate of degradation of 97% for PCL meshes. In an in vivo scenario, the degradation was slower, although the samples were not rejected, and were well-integrated in the surrounding tissues inside the subcutaneous pockets specifically created.
- Experimental assessment of hybrid mould performancePublication . Pontes, Antonio J.; Queirós, Miguel P.; Martinho, Pedro G.; Bártolo, Paulo J.; Pouzada, António S.Hybrid moulds are a novel approach for rapid tooling of injection moulds that combines conventional machining for the mould structure and rapid prototyping techniques for the moulding blocks (core and cavity). In this study, two routes were used for producing the moulding blocks: selective laser sintering of stainless steel-based powder (hard tool) and epoxy resin vacuum casting (soft tool). The experimental work was based on a complex tridimensional commercial part. The mouldings were made in polypropylene, and the processing performance was monitored online in terms of pressure and temperature at the impression. The performance of the moulding blocks was analysed in terms of thermal and cycle performance and structural integrity. The epoxy tooling route is more adequate for fine detailing than selective laser sintering but is not adequate for parts with extensive ribs or deep bosses. The structural integrity of the less costly epoxy composite can be compromised during ejection, this suggesting the need to evaluate the stress field by simulation at the design stage of the mould.
- Extruded bioreactor perfusion culture supports the chondrogenic differentiation of human mesenchymal stem/stromal cells in 3D porous poly(ɛ-caprolactone) scaffoldsPublication . Silva, João C.; Moura, Carla; Borrecho, Gonçalo; Matos, António P. Alves de; Silva, Cláudia L. da; Cabral, Joaquim M. S.; Bártolo, Paulo J.; Linhardt, Robert J.; Ferreira, Frederico CasteloNovel bioengineering strategies for the ex vivo fabrication of native-like tissue-engineered cartilage are crucial for the translation of these approaches to clinically manage highly prevalent and debilitating joint diseases. Bioreactors that provide different biophysical stimuli have been used in tissue engineering approaches aimed at enhancing the quality of the cartilage tissue generated. However, such systems are often highly complex, expensive, and not very versatile. In the current study, a novel, cost-effective, and customizable perfusion bioreactor totally fabricated by additive manufacturing (AM) is proposed for the study of the effect of fluid flow on the chondrogenic differentiation of human bone-marrow mesenchymal stem/stromal cells (hBMSCs) in 3D porous poly(ɛ-caprolactone) (PCL) scaffolds. hBMSCs are first seeded and grown on PCL scaffolds and hBMSC–PCL constructs are then transferred to 3D-extruded bioreactors for continuous perfusion culture under chondrogenic inductive conditions. Perfused constructs show similar cell metabolic activity and significantly higher sulfated glycosaminoglycan production (≈1.8-fold) in comparison to their non-perfused counterparts. Importantly, perfusion bioreactor culture significantly promoted the expression of chondrogenic marker genes while downregulating hypertrophy. This work highlights the potential of customizable AM platforms for the development of novel personalized repair strategies and more reliable in vitro models with a wide range of applications.
- Numerical Calculations in Tissue EngineeringPublication . Almeida, Henrique de Amorim; Bártolo, Paulo J.The design of optimized scaffolds for tissue engineering is a key topic of research, as the complex macro- and micro- architectures required for a scaffold depends not only on the mechanical properties, but also on the physical and molecular queues of the surrounding tissue within the defect site. Thus, the prediction of optimal features for tissue engineering scaffolds is very important for its mechanical, vascular or topological properties. The relationship between high scaffold porosity and high mechanical properties is contradictory, as it becomes even more complex due to the scaffold degradation process. A scaffold design strategy was developed, based on the finite element method, to optimise the scaffold design regarding the mechanical and vascular properties as a function of porosity. Scaffolds can be considered as a LEGO structure formed by an association of small elementary units or blocks. In this research work, two types of family elementary scaffold units were considered: non-triple periodic minimal surfaces and triple periodic minimal surfaces that describe natural existing surfaces. The main objective of this work is to present the undergoing research based on numerical simulations for the evaluation and prediction of the scaffold's behaviour under structural and vascular loading, and its topological optimisation.
- Optimization of Thermoplastic Pre-Pregs OvermouldingPublication . Carreira, Pedro; Alves, Nuno; Carina Ramos; Bártolo, Paulo J.The search for new technological concepts in the field of injection of thermoplastic polymers, in order to optimize the process and reduce cycle time, faced us with a new concept in moulding, where two different technologies are proposed to be unified. The fabric impregnated with thermoplastic is an example of a quite new product that combines the potential of polymers with long reinforcing fibres. In order to process this new product, injection of polymers and thermoforming will be applied in only one operation. To allow cycle time prediction for this new technique, changes will be made in the formulation of conventional injection cycle time, in order to comprise the new necessary stages. In this work a new approach is proposed to obtain moulded parts of thermoplastic polymers with functional fabric only in a single processing cycle. The description of the new stages and its mathematical formulation is made, in function of the time needed to complete each one. The results presented come from processing parameters optimization using the Particle Swarm Optimization (PSO) algorithm.