Transcript Silk Sericin: A Versatile Material for Tissue Engineering and Drug

SILK SERICIN:
MATERIAL
ENGINEERING
DELIVERY
Huma Mehreen Sadaf
10-arid-1824
Department of Botany
A
FOR
AND
VERSATILE
TISSUE
DRUG
BACKGROUND..
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Tissue
engineering
is
to
improve
the
understanding of tissue pathology to improve or
sustain tissue function.
Choice of suitable biomaterials is crucial because
they must replicate the biological and mechanical
functions of the natural extracellular matrix
(ECM), thereby representing an artificial ECM.
In this regard, growing efforts have been devoted
to the study of naturally derived materials
because they are biocompatible and have the
potential advantage of biological recognition.
BACKGROUND..

Recently, interest in biomaterials research has
shifted
increasingly
toward
functional
biomaterials,
targeting
applications
in
regenerative medicine through the development
of improved tissue scaffolds, and toward new
drug delivery systems.
INTRODUCTION…
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Silk sericin (SS) is one of the two major proteins
forming the silkworm cocoon,
the other one is silk fibroin.
In the cocoon, fibroin is a fibrous protein in the
form of a delicate twin thread and enveloped by
successive sticky layers of SS forming the silk.
CONTD…
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In the silk industry, SS is removed from fibroin
to improve the luster, softness, smoothness,
whiteness, and dyeability of the fibers while SS is
discarded in wastewater.
CONTD…
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Indeed, SS is an unutilized by-product of the
textile industry.
SS has recently been proven to exhibit important
biological activities, making it potentially useful
in
pharmacological,
cosmetic,
and
biotechnological applications.
Accordingly, much effort has been dedicated to
the recovery of SS from industrial wastewater.
EXTRACTION…
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Sericin, also known as “silk glue”, is a globular
protein.
In the textile industry, SS is separated from
fibroin via the “degumming” of the cocoons and is
discharged in wastewater.
Several methods based on heat treatment are
currently available for the extraction of SS from
silk cocoons.
BIOCOMPATIBILITY AND IMMUNOLOGICAL
RESPONSE
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A significant consideration in the
application of any biomaterial is
its potential activation of the
immune
system
i.e.
its
biocompatibility.
This is in fact one of the main
determinants of the success or
failure of a biomaterial in tissue
engineering
and
regenerative
medicine applications.
CONTD…
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The innate immune system is the first
barrier to any foreign body in the host and
as such, it plays an important role in
determining the course of a potential
immune response to foreign substances.
Therefore, macrophage response through
the expression and release of first-response
pro-inflammatory cytokines is most often
assessed in the biocompatibility evaluation
of materials.
CONTD…
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Sericin was reported to be immunologically inert on the
basis that in its soluble form, it failed to induce, the
short- and long-term expression and release TNF-α.
When associated with crystalline fibroin, triggered
significant release of TNF-α from macrophages in
comparison with SS alone under the same conditions.
CONTD…
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This indicates that SS-mediated activation is
dependent on physical association with the core
fibroin fibers.
Moreover, SS did not trigger the production of anti-SS
antibodies after intravenous injection in rabbits.
ABILITY TO PROMOTE CELL
PROLIFERATION…
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Serum-free media was supplemented with SS to
culture different cells including:
Human epithelial cells
Human embryonic kidney transformed cells
Human hepatoblastoma cells
Murine hybridoma
It significantly promoted the growth of these cell
lines by shortening the lag phase of the cell cycle
and by inducing early entrance of the cultures in
their logarithmic phase.
SS-BASED BIOMATERIALS FOR TISSUE
ENGINEERING
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The polar side chains of SS enable the easy crosslinking and blending of SS with other polymers to
yield improved biodegradable materials.
Several of
techniques are often combined to
fabricate SS matrices comprising films, scaffolds,
and hydrogels.
Stable biomaterials are thus fabricated while
achieving the controlled release of soluble SS,
which
promotes
cell
growth
and
tissue
regeneration.
BONE TISSUE ENGINEERING
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SS also attracted much attention in bone tissue
engineering. SS was indeed found to effectively
promote the growth and proliferation of
osteoblasts, which adhered and spread well on
SS-coated surfaces.
EFFECT OF SS ON SKIN TISSUES
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Macroscopically, ROS generation due to chronic
exposure of the skin to UV radiation ultimately results
in premature skin aging expressed as wrinkle
formation, along with hyper-pigmentation and the
formation of sunburn cells.
SS has skin moisturizing and anti-wrinkle effects,
which are due to its high serine content, and its AA
composition is very similar to that of the skin’s natural
moisturizing factor (NMF).
This has led to the use of SS not only in the biomedical
field but also in the food and cosmetics industries.
SKIN TISSUE REPAIR WITH SS-BASED
MATERIALS…
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Notably, some skin repair and wound
healing materials incorporating SS have
already been developed and several
clinical trials have been reported
whereby SS enhanced the adhesion,
migration, and growth of keratinocytes
and fibroblasts, increased collagen
production,
and
improved
reepithelialization in skin wounds.
Actually, due to the numerous materials
proposed in this regard, more clinical
trials are to be expected.
WOUND HEALING AND TISSUE
REGENERATION…
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For the growth of keratinocytes and fibroblasts in
particular, this has led to new applications of SS in
regenerative
medicine
and
as
wound-healing
biomaterials.
These cells, aside from producing regulatory cytokines
for the wound healing process, are involved in the reepithelialization and the production of ECM proteins
that play critical roles in healing.
SS: A VEHICLE FOR DRUG DELIVERY…
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Delivery systems are used to improve the effects
of active compounds by targeting their delivery
site to achieve the desired bioactivity.
Owing to its amphiphilic character (polar side
chains and hydrophobic domains), SS may be
used as a vehicle as it easily binds charged
molecules.
Because of their amphiphilic character, the
particles efficiently trapped both hydrophobic
and hydrophilic drugs.
CONTD…
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Several SS formulations (films, gels, and
sponges) for drug delivery application were
reported.
The drug release rate was controlled by the type
of formulation and SS concentration.
Additionally, their small size increase the
availability of loaded drugs to less accessible
areas such as deeper tissues.
CONCLUSIONS…
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SS has been a material of great interest in recent
years because of its prospective biomedical and
biotechnological applications.
Its potential lies in its biochemical and
biophysical properties, which vary with the
source and method of protein isolation.
SS is hence a unique protein due to its properties,
and accordingly it has been widely applied in
tissue engineering.
FUTURE PROSPECTS…
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SS could serve as a vehicle for cell
transplantation and as a proliferative inducer.
New advancements are likewise needed for the
applications of SS in drug delivery systems to
take advantage of its interesting properties.
However, due to the large amounts of SS
eliminated in the silk wastewaters, the cost of its
recovery from the silk industry remains high,
requiring the development of more efficient and
cheaper methods to alleviate this concern.
REFERENCE…
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Lallepak L., G. Mario, Y. Guang, W. Qun. Silk
sericin: A versatile material for tissue
engineering and drug delivery, Biotechnology
Advances: 1-40, 2015.