Tissue engineering is a scientific field that refers to
the practice of combining scaffolds, cells and biologically active molecules to
form functional tissues.� The knowledge
from this area can be used to facilitate clinical procedures involving repair of
damaged tissues and organs. In addition to natural biomaterials, which include
collagen, gelatin, silk protein-based biomaterials or cellulose-, glucose-,
chitosan polysaccharide-based biomaterials, synthetic materials like
bio-textiles have attracted great attention as potential fabrication methods
for engineered tissue constructs. Some examples of the commercial bio-textiles
in market include Tigr Matrix, Ultrapro and Intergard, which are used to treat
pelvic organ prolapse, hernia and vascular diseases. Generally, bio-textiles
can be divided into four categories: synthetic, hydrogel-based, natural, and
composite fibres.
1.
Synthetic
fibres are used in vascular prosthesis, cartilage scaffolds, and
tissue-engineered bladder due to their high mechanical strength and
controllable surface morphology, which can help in better interaction of the
material with the host tissue. Micro and nano synthetic fabricated fibres have
the ability to mimic the intricate fibrillar microstructure of the natural
extracellular matrix (ECM). The fibrous synthetic fibres can be fabricated
through electrospinning or blow spinning. These methods are advantageous for
fabricating cardiovascular or skin scaffolds where mechanical strength is
required. However, synthetic fibres lack the ability to encapsulate cells.
2.
Hydrogel
based fibres find their application in soft tissue engineering, drug delivery
and implantable sensors. Hydrogels are 3D polymeric structures capable of
collapsing and re-swelling in response to different environmental stimuli in
vivo, such as pH, temperature, electric fields and enzyme substrates. These
materials provide a viable and nurturing environment for the cells to grow and
proliferate. Wetspinning and microfluidic spinning are two approaches through
which hydrogel-based fibres can be fabricated. Microfluidic spinning generally
offers better control over fibre shape and size compared to wetspinning.
3.
Natural
fibres like protein or polysaccharide-based fibres are highly biocompatible and
degrade into harmless products inside the body. Collagen threads used for
degradable sutures can be manufactured by wetspinning or meltspinning methods.
Chitosan with anti-bacterial properties is used in drug delivery and wound
healing applications. These fibres are usually fabricated using wetspinning or
electrospinning methods. Another example is the use of silk fibroin (SF) yarns
processed into weft-knitted fabrics spaced by a monofilament of polyethylene
terephthalate (PET) to treat bone loss in the craniofacial complex.
4.
Composite
fibres are a combination of two or more constituent materials. Each constituent
part of the composite material remains distinct and serves a specific function.
In hybrid systems, on the other hand, the constituents can be mixed throughout
the 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 the
tissue construct can be controlled through knitting, weaving or braiding
textile 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.