12.7 Applications
277
offers the advantage of making more complex and more detailed and dimensionally
precise design of these scaffolds more possible. This will result in bone regrowth
which is as close to the original tissue as possible. Materials used for these include
polycaprolactone and hydroxyapatite composite (Liu et al. 2019). Such scaffolds
have been tested in vitro and in vivo on laboratory animals (commonly regeneration
of bones in damaged rat skull regions). The use of hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 )
is with the aim of using a material which is the same as that found in the bone tissue.
It acts as the dispersed phase in the composite while the polymer acts as the matrix.
The membranes or scaffolds could be required to remain in place for different
periods of time; therefore, the collagen material needs to be designed for specific
applications. This is done by for example varying the degree of cross-linking which
in turn affects the rate of degradation (Moses et al. 2008). Composites of collagen
with varying degree of degradation could also be used. Most of the commercially
available tissue scaffolds are based on bovine and porcine-based collagen, and fish
waste could potentially replace or augment the use of bovine or porcine collagen
in tissue regeneration. Many aquatic vertebrates including fish collagen, like human
collagen, are mostly of type 1 (Zhang et al. 2018). Collagen alone usually does not
possess sufficient mechanical properties to act as a scaffold or membrane for tissue
regeneration; it is therefore often used as a composite alongside other materials such
as carbon, minerals or other polymers. The mechanical properties can also be further
enhanced by cross-linking with crosslinkers such as glutaraldehyde or ribose (Bai
et al. 2018).
12.7.4 Biomedical Implants
The biocompatibility of collagen makes it an excellent material for implants and
tissue replacement. An example of such is in corneal implants into the eye. Corneal
repair generally requires replacement of the damaged cornea with an artificial one
which is implanted into the eyes to replace the old one. The material from which
such is made needs to be biocompatible and be retained in the eye and allow growth
and proliferation of new corneal cells. Fish scales have been tested as ideal candidate
as a biocompatible corneal replacement. Scales from the collagen-based artificial
cornea have the advantage of not requiring human corneal donor, and it eliminates
the chance of an undesired immune response. Obtaining this from a widely available
resource such as fish scales which is not limited to only a particular region also offers
the prospect of having multiple producers across the world. The arrangement of the
collagen structure is quite important in tissue regeneration as the micro- and nanostructure must allow sufficient space for oxygen transport to the cells growing within
and also allow for cell adhesion. To address this, a similar material which already
possesses an extracellular matrix structure similar to the microporous structure of
the cornea is used. This approach was used by Lin et al. (2010). Scales from tilapia
fish were decalcified using nitric acid treatment and living behind the organic part
which comprises of collagen. With the calcified part of the scales removed, what is
277
offers the advantage of making more complex and more detailed and dimensionally
precise design of these scaffolds more possible. This will result in bone regrowth
which is as close to the original tissue as possible. Materials used for these include
polycaprolactone and hydroxyapatite composite (Liu et al. 2019). Such scaffolds
have been tested in vitro and in vivo on laboratory animals (commonly regeneration
of bones in damaged rat skull regions). The use of hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 )
is with the aim of using a material which is the same as that found in the bone tissue.
It acts as the dispersed phase in the composite while the polymer acts as the matrix.
The membranes or scaffolds could be required to remain in place for different
periods of time; therefore, the collagen material needs to be designed for specific
applications. This is done by for example varying the degree of cross-linking which
in turn affects the rate of degradation (Moses et al. 2008). Composites of collagen
with varying degree of degradation could also be used. Most of the commercially
available tissue scaffolds are based on bovine and porcine-based collagen, and fish
waste could potentially replace or augment the use of bovine or porcine collagen
in tissue regeneration. Many aquatic vertebrates including fish collagen, like human
collagen, are mostly of type 1 (Zhang et al. 2018). Collagen alone usually does not
possess sufficient mechanical properties to act as a scaffold or membrane for tissue
regeneration; it is therefore often used as a composite alongside other materials such
as carbon, minerals or other polymers. The mechanical properties can also be further
enhanced by cross-linking with crosslinkers such as glutaraldehyde or ribose (Bai
et al. 2018).
12.7.4 Biomedical Implants
The biocompatibility of collagen makes it an excellent material for implants and
tissue replacement. An example of such is in corneal implants into the eye. Corneal
repair generally requires replacement of the damaged cornea with an artificial one
which is implanted into the eyes to replace the old one. The material from which
such is made needs to be biocompatible and be retained in the eye and allow growth
and proliferation of new corneal cells. Fish scales have been tested as ideal candidate
as a biocompatible corneal replacement. Scales from the collagen-based artificial
cornea have the advantage of not requiring human corneal donor, and it eliminates
the chance of an undesired immune response. Obtaining this from a widely available
resource such as fish scales which is not limited to only a particular region also offers
the prospect of having multiple producers across the world. The arrangement of the
collagen structure is quite important in tissue regeneration as the micro- and nanostructure must allow sufficient space for oxygen transport to the cells growing within
and also allow for cell adhesion. To address this, a similar material which already
possesses an extracellular matrix structure similar to the microporous structure of
the cornea is used. This approach was used by Lin et al. (2010). Scales from tilapia
fish were decalcified using nitric acid treatment and living behind the organic part
which comprises of collagen. With the calcified part of the scales removed, what is