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- Biofabrication Strategies for Tissue EngineeringPublication . Bártolo, Paulo Jorge; Domingos, Marco; Patrício, Tatiana; Cometa, Stefania; Mironov, Vladimir; Bártolo, Paulo JorgeThe success of Tissue Engineering (TE) strongly relies on the capability of designing biomimetic scaffolds closely resembling the host tissue environment. Due to the functional multitude of the native tissues, the considerations are complex and include chemical, morphological, mechanical and biological factors and their mutability with time. Nonetheless, to trigger and/or assist the “natural healing mechanism’’ of the human body it seems essential to provide an appropriate biomechanical environment and biomolecular signalling to the cells. Novel biomanufacturing processes are increasingly being recognized as ideal techniques to produce 3D biodegradable structures with optimal pore size and spatial distribution, providing an adequate mechanical support for tissue regeneration while shaping in-growing tissues. In this chapter, we discuss in detail the most recent advances in the field of biofabrication, providing and updated overview of processes and materials employed in the production of tissue engineering constructs. Bioprinting or ‘’scaffold-less’’ strategies are also presented in this work. They are based on the precise deposition of high-density tissue spheroids or cell aggregates being advantageous alternatives to the current scaffold-based tissue engineering approach.
- 3D shape prior active contours for an automatic segmentation of a patient specific femur from a CT scanPublication . Almeida, D.; Folgado, J.; Fernandes, P.R.; Ruben, RuiThe following paper describes a novel approach to a medical image segmentation problem. The fully automated computational procedure receives as input images from CT scan exams of the human femur and returns a three dimensional representation of the bone. This patient specific iterative approach is based in 3D active contours without edges, implemented over a level set framework, on which the evolution of the contour depends on local image parameters which can easily be defined by the user but also on a priori information about the volume to segment. This joint approach will lead to an optimal solution convergence of the iterative method. The resulting point cloud can be an excellent starting point for a Finite Element mesh generation and analysis or the basis for a stereolitography for example.
- Recent Advances in Additive BiomanufacturingPublication . Pereira, Rúben Filipe Brás; Bartolo, PauloThe principles of tissue engineering and regenerative medicine have been used for the development of innovative medical therapies for engineering tissues and organs. These therapies involve the use of biomaterials, cells, and biologically active molecules, according to two fundamental strategies: the top-down and bottom-up approaches. Top-down approaches, which are the most commonly used, involve the implantation of porous scaffolds, with or without living cells and bioactive agents, into the defect site in the patient. In these approaches, scaffolds act as temporary templates for the seeded cells, mimicking the properties of the native extracellular matrix and providing an adequate environment for the growth of the new tissue. Scaffolds can be produced by using either conventional or additive techniques, resulting in structures with different levels of porosity, pore size, interconnectivity, and spatial distribution. Additive biomanufacturing techniques allow significantly more control over the scaffold characteristics (e.g., architecture, porosity, permeability, etc.), enabling the automatic and reproducible fabrication of scaffolds in a wide range of polymeric, ceramic, and composite materials. Some of these techniques also allow the fabrication of constructs encapsulating living cells. This chapter describes the most recent advances in the top-down approach to fabricate scaffolds for tissue regeneration, presenting the most important additive biomanufacturing techniques and processable materials. Future perspectives in the field and challenges for future research are also discussed.
- Photocrosslinkable Materials for the Fabrication of Tissue-Engineered Constructs by StereolithographyPublication . Pereira, Rúben F.; Bártolo, Paulo J.Stereolithography is an additive technique that produces three-dimensional (3D) solid objects using a multi-layer procedure through the selective photoinitiated curing reaction of a liquid photosensitive material. Stereolithographic processes have been widely employed in Tissue Engineering for the fabrication of temporary constructs, using natural and synthetic polymers, and polymer-ceramic composites. These processes allow the fabrication of complex structures with a high accuracy and precision at physiological temperatures, incorporating cells and growth factors without significant damage or denaturation. Despite recent advances on the development of novel biomaterials and biocompatible crosslinking agents, the main limitation of these techniques are the lack number of available photocrosslinkable materials, exhibiting appropriate biocompatibility and biodegradability. This chapter gives an overview of the current state-of-art of materials and stereolithographic techniques to produce constructs for tissue regeneration, outlining challenges for future research.
- PrefacePublication . Fernandes, Paulo Rui; Bártolo, Paulo JorgeThis book is a contribution for Tissue Engineering seen as multidisciplinary field involving scientists from different backgrounds like medicine, chemistry, material science, engineering and biology with a focus on the development of mathematical methods that are quite relevant to understand cell biology and human tissues as well to model, design and fabricate optimized and smart scaffolds.
- Permeability Evaluation of Flow Behaviors Within Perfusion BioreactorsPublication . Freitas, D.; Almeida, H.A.; Bártolo, P. J.Tissue engineering aims to produce artificial tissue in order to create or repair damaged tissue. It is evident that scaffolds are of extreme importance, because they will be the support structure of the new tissue. This new tissue is cultivated in vitro in a bioreactor in which is placed the scaffold. In order to control the cell culture process inside of a bioreactor, it is essential to know the fluid flow inside the scaffold for an adequate exchange of nutrients and metabolic waste. A novel multifunctional bioreactor with a perfusion system module comprised of three different inlet and outlet membranes is being developed. This research work will evaluate the permeability of the scaffold under the three different inlet and outlet diffusion membranes of the culture chamber.
- Electrospinning for Medical ApplicationsPublication . Song, Wenhui; Mitchell, Geoffrey R.; Burugapalli, KrishnaThere is a natural connection between a variety of electrospun fibres and biomedical applications. The most commonly quoted application of electrospun fibres is their use as scaffolds in tissue engineering for regenerative medicine. There are also many other applications, which include drug delivery systems, membrane systems and analytical functionality. This chapter identifies the key challenges in each of these topics, as well as the particular role of electrospun fibres in addressing these challenges.
- Chapter 8: Structure Development in Electrospun FibresPublication . Mitchell, Geoffrey R.; Mohan, Saeed D.; Davis, Fred J.; Ahn, Kyung-Hwa; Al-Azab, Mohamed; El Hadi, Ahmed; Elliott, Delyth; Kariduraganavar, Mahadevappa Y.; Nagarajan, Anitha; Nazhipkyzy, Meruyert; Geoffrey R MitchellElectrospinning is a process which transforms polymer solutions in to solid fibres in ∼25 ms. In the case of an amorphous polymer, the resultant molecular organisation may not be so different from that of the solution. However, polymers are rich in different types of ordering processes and these may be encountered during electrospinning. In many areas of polymer processing, the processing procedures can have a significant impact on the structure and hence properties of the final product as the selection of the chemical configuration
- IntroductionPublication . Davis, Fred J.; Mohan, Saeed D.; Ibraheem, Muaathe A.This chapter provides a basic introduction to the topics described in this book. The principles of electrospinning, in terms of the influence of an electric field on a droplet of polymer melt or solution is introduced, and a review of some of the experimental parameters, and their relationship towards the properties of the fibres produced is given. A brief summary of the types of materials that can be electrospun is included, together with methods for their characterisation. Finally, a short review of potential applications for electrospun fibres is discussed.
- Chapter 13. Future Perspectives on ElectrospinningPublication . Mitchell, Geoffrey R.; Sperrin, MalcolmAlthough the origins of electrospinning date back over 100 years, it is intense activity in the last 21 years which has led to considerable improvements in our knowledge of electrospinning and the broad-ranging opportunities for commercial application. The recent development of melt electrospinning provides a new additive manufacturing tool, providing routes to structures from nanometres to millimetres. Here, we consider where this rollercoaster of a topic is heading and its future prospects.
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