3 results
18 - Microfabricated gels for tissue engineering
- from Part III - Hydrogel scaffolds for regenerative medicine
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- By Gulden Camci-Unal, Harvard Medical School, Jesper Hjortnaes, Harvard Medical School, Hojae Bae, Harvard Medical School, Mehmet Remzi Dokmeci, Harvard Medical School, Ali Khademhosseini, Harvard Medical School
- Edited by Peter X. Ma, University of Michigan, Ann Arbor
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- Book:
- Biomaterials and Regenerative Medicine
- Published online:
- 05 February 2015
- Print publication:
- 24 July 2014, pp 317-331
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Summary
Introduction
Tissue engineering aims to develop biological substitutes that repair or replace damaged tissues or whole organs by combining technologies from engineering and medical sciences [1]. Although tissue engineering has enabled successful generation of various artificial tissue substitutes, such as skin [2], bladder [3], cartilage [4], bone [5], heart valves [6], and blood vessels [7], a number of challenges remain to be solved. It has been challenging to engineer large and vascularized organs such as the heart or liver. These tissues depend on adequate vascularization for the supply of nutrients and oxygen. In tissue engineering, this translates into not only creating the specific tissue but also making the highly organized vasculature. On the other hand, avascular tissues such as heart valves or cartilage depend on adequate diffusion for their supply of nutrients and oxygen. In terms of engineering, an avascular biomimetic construct cannot be too thick [8, 9], since this would lead to a limited supply of nutrients and oxygen [1]. Microfabrication strategies aim to overcome these limitations by controlling the size, geometry and features of three-dimensional (3D) in-vitro tissue-engineered constructs. Recent advances in biomaterials combined with developments in microengineering methods have enabled the development of vascular networks, prevascularized tissue constructs, and creation of well-ordered tissue constructs from microgel units with different cell types. [10].
Native tissues consist of cells that reside in a framework called the extracellular matrix (ECM). The ECM is composed of proteins (e.g. collagen), fibers (e.g. elastin), polysaccharides (e.g. hyaluronic acid), glycosaminoglycans (e.g. heparan sulfate), and growth factors (e.g. fibroblast growth factor). The ECM functions as a support system for cells to exert their biological function and can be viewed as the scaffolding environment for the tissues. Traditional tissue engineering uses synthetic scaffolds or biomaterials as molds to create tissue constructs. These scaffolds are typically porous, biocompatible, and degradable, and allow sufficient diffusion to occur [11]. Furthermore, such scaffolds enable cell adhesion, proliferation, and differentation, and tissue organization that are similar to those in their native counterparts [12]. Over time, the synthetic scaffold will degrade in vivo, while the cells deposit new natural scaffolding (ECM), thus leading to the formation of new tissue.
Dielectrophoretical fabrication of hybrid carbon nanotubes-hydrogel biomaterial for muscle tissue engineering applications
- Javier Ramón-Azcón, Samad Ahadian, Raquel Obregon, Hitoshi Shiku, Ali Khademhosseini, Tomokazu Matsue
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1621 / 2014
- Published online by Cambridge University Press:
- 30 January 2014, pp. 81-86
- Print publication:
- 2014
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- Article
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Dielectrophoresis (DEP) approach was employed to achieve highly aligned multi-walled carbon nanotubes (MWCNTs) within the gelatin methacrylate (GelMA) hydrogels in a facile, rapid, inexpensive, and reproducible manner. This approach enabled us to make different CNTs alignments (e.g., vertical or horizontal alignments) within the GelMA hydrogel using different electrode designs or configurations. Anisotropically aligned GelMA-CNTs hydrogels showed considerably higher conductivity compared to randomly distributed CNTs dispersed in the GelMA hydrogel and the pristine and non-conductive GelMA hydrogel. Adding 0.3 mg/mL CNTs to the GelMA hydrogel led to a slight increase in the mechanical properties of the GelMA and made it to behave as a viscoelastic material. Therefore, it can be used as a suitable scaffold for soft tissues, such as skeletal muscle tissue. 3D microarrays of skeletal muscle myofibers were then fabricated based on the GelMA and GelMA-CNTs hydrogels and they were characterized in terms of gene expressions related to the muscle cell differentiation and contraction. Owing to high electrical conductivity of aligned GelMA-CNTs hydrogels, the engineered muscle tissues cultivated on these materials demonstrated superior maturation and functionality particularly after applying the electrical stimulation (voltage 8 V, frequency 1 Hz, and duration 10 ms for 2 days) compared to the corresponding tissues obtained on the pristine GelMA and randomly distributed CNTs within the GelMA hydrogel.
Chapter 4 - Microfabrication techniques in materiomics
- Edited by Jan de Boer, University of Twente, Enschede, The Netherlands, Clemens A. van Blitterswijk, University of Twente, Enschede, The Netherlands
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- Book:
- Materiomics
- Published online:
- 05 April 2013
- Print publication:
- 02 May 2013, pp 51-66
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Summary
Scope
This chapter deals with an overview of basic microfabrication techniques. The goal is to explain to the reader how such techniques can be utilized in the field of materiomics. The basic processes used in microfabrication including photolithography, etching, electron beam lithography and micromoulding are explained. Some classic examples of these techniques as applied to materiomics are also shown. Furthermore, possible uses of such techniques, and the development and application of hybrid techniques to be able to answer fundamental questions about biological behaviour of materials, are also suggested.
Basic principles of microfabrication
Introduction
Techniques used to fabricate structures or devices smaller than 100 µm are commonly referred to as microfabrication techniques. Initially meant for the electronics industry, they have found a wide range of applications in diverse fields such as chemical engineering and the life sciences. Since the early 1990s, the application of microfabrication technologies in the area of chemical and biological analysis has been termed ‘micro total analysis systems’ (µTAS) (1). Microfabricated devices meant for µTAS initially offered the advantage of sample analysis on the microscale, but over the years, the evolution of these technologies has led to the facilitation of sample preparation, fluid handling, separation systems, cell handling and cell culturing in an integrated manner (1). The application of microtechnologies for the fabrication of devices or systems to study material properties benefits from cost efficiency, high performance, precision-based design flexibility, miniaturization and automated analysis. Miniaturization involves the convergence of multiple disciplines, such as fluid dynamics, material sciences, engineering and the life sciences, that need to join expertise in order to design functional systems. Moreover, these devices can be used to evaluate biological behaviour in vitro and can help us to test thousands of different biomaterials and surface properties without the complexity related to in vivo assays.