Tissue engineering is a scientific field that refers tothe practice of combining scaffolds, cells and biologically active molecules toform functional tissues.� The knowledgefrom this area can be used to facilitate clinical procedures involving repair ofdamaged tissues and organs. In addition to natural biomaterials, which includecollagen, gelatin, silk protein-based biomaterials or cellulose-, glucose-,chitosan polysaccharide-based biomaterials, synthetic materials likebio-textiles have attracted great attention as potential fabrication methodsfor engineered tissue constructs. Some examples of the commercial bio-textilesin market include Tigr Matrix, Ultrapro and Intergard, which are used to treatpelvic organ prolapse, hernia and vascular diseases. Generally, bio-textilescan be divided into four categories: synthetic, hydrogel-based, natural, andcomposite fibres.

1.      Syntheticfibres are used in vascular prosthesis, cartilage scaffolds, andtissue-engineered bladder due to their high mechanical strength andcontrollable surface morphology, which can help in better interaction of thematerial with the host tissue. Micro and nano synthetic fabricated fibres havethe ability to mimic the intricate fibrillar microstructure of the naturalextracellular matrix (ECM). The fibrous synthetic fibres can be fabricatedthrough electrospinning or blow spinning. These methods are advantageous forfabricating cardiovascular or skin scaffolds where mechanical strength isrequired. However, synthetic fibres lack the ability to encapsulate cells.

2.     Hydrogelbased fibres find their application in soft tissue engineering, drug deliveryand implantable sensors. Hydrogels are 3D polymeric structures capable ofcollapsing and re-swelling in response to different environmental stimuli invivo, such as pH, temperature, electric fields and enzyme substrates. Thesematerials provide a viable and nurturing environment for the cells to grow andproliferate. Wetspinning and microfluidic spinning are two approaches throughwhich hydrogel-based fibres can be fabricated. Microfluidic spinning generallyoffers better control over fibre shape and size compared to wetspinning.

3.     Naturalfibres like protein or polysaccharide-based fibres are highly biocompatible anddegrade into harmless products inside the body. Collagen threads used fordegradable sutures can be manufactured by wetspinning or meltspinning methods.Chitosan with anti-bacterial properties is used in drug delivery and woundhealing applications. These fibres are usually fabricated using wetspinning orelectrospinning methods. Another example is the use of silk fibroin (SF) yarnsprocessed into weft-knitted fabrics spaced by a monofilament of polyethyleneterephthalate (PET) to treat bone loss in the craniofacial complex.

4.     Compositefibres are a combination of two or more constituent materials. Each constituentpart of the composite material remains distinct and serves a specific function.In hybrid systems, on the other hand, the constituents can be mixed throughoutthe construct. The combination typically results in improved strength,toughness and stiffness of the biomaterial.

For the above four subcategories of bio-textiles,microstructure, mechanical properties and the cellular distribution of thetissue construct can be controlled through knitting, weaving or braidingtextile method. These are shown below in figure 1.

The knitted structure is highly flexible and can be constructed into a 3D complex structure, however it becomes difficult to adjust properties in different directions. As an example, knitted structures like the knitted silk collagen sponge scaffolds have been used in tendon and ligament regeneration.� Weaving method offers the ability to create structures with anisotropic properties. However, it is less flexible compared to the knitted structure. Woven structures mimic the properties of cardiac tissues and the cartilage. Lastly, braided structures possess excellent flexibility and are good for load bearing tissues. Hence, braided structures can be used for load bearing fixations and wound closure applications.

It is clear that bio-textiles have a great potential in various applications in the tissue engineering field. Different textile techniques that have the ability to control the microstructure make bio-textiles a suitable tool for various medical applications. Despite advancements in the area of bio-textiles, implantable fabrics still have limited applications due to inability to capture the in vivo environment using synthetic fibres. This challenge can be addressed with the use of advanced biomaterials by incorporating properties that will lead to better host-material interaction and integration. ���

References:

1.       Tissue Engineering and Regenerative Medicine. (2013, July 22). Retrieved October 7, 2018, from https://www.nibib.nih.gov/science-education/science-topics/tissue-engineering-and-regenerative-medicine

2.      Akbari, M., Tamayol, A., Bagherifard, S., Serex, L., Mostafalu, P., Faramarzi, N., Khademhosseini, A. (2016). Textile Technologies and Tissue Engineering: A Path Toward Organ Weaving. Advanced Healthcare Materials, 5(7), 751-766. https://doi.org/10.1002/adhm.201500517

3.      Ribeiro, V. P., Silva-Correia, J., Nascimento, A. I., da Silva Morais, A., Marques, A. P., Ribeiro, A. S., � Reis, R. L. (2017). Silk-based anisotropical 3D biotextiles for bone regeneration. Biomaterials,123, 92-106. https://doi.org/10.1016/j.biomaterials.2017.01.027��� ����������

About the author: Simran Dayal is a final year undergraduate student of biomedical engineering at the University of Tennessee, Knoxville, USA. Her areas of interest include tissue engineering, regenerative medicine, biomaterials and gene therapy & drug delivery systems.