Artificial skin is
skin grown
in a laboratory. It can be used as skin replacement for people who have
suffered
skin trauma, such as severe
burns or
skin diseases, or other purposes.
Background
The skin is the largest
organ in the
human body.[1]
Skin is made up of two layers, the epidermis and the dermis. The
epidermis is the outer layer of skin that keeps vital fluids in and
harmful bacteria out of the body. The dermis is the inner layer of skin
that contains blood vessels, nerves, hair follicles, oil, and sweat
glands.[2]
Severe damage to large areas of skin exposes the human organism to
dehydration and
infections that can result in death.
Traditional ways of dealing with large losses of skin have been to
use skin grafts or from a different person/cadaver. The former approach
has the disadvantage that there may not be enough skin available, while
the latter suffers from the possibility of
rejection or infection. Until the late twentieth century, skin
grafts were constructed from the patient's own skin. This became a
problem when skin was too far damaged or when too much of the organ was
ruined.[3]
Synthetic skin was invented by John F. Burke, chief of Trauma
Services in Massachusetts General Hospital. He was assisted by Ioannis
V. Yannas, a chemistry professor at Massachusetts Institute of
Technology, Cambridge, Massachusetts. In the 1970s, they created a
polymer with collagen fibers and sugar molecules. A small porous was
formed. When the porous was placed on the wound, skin cells around it
seemed to encourage a faster healing process. This allowed the healing
process to continue at a much faster rate. They also created a skin from
shark cartilage and cowhide. When this skin dried and was sterilized, it
could be made into a thin membrane in which materials could pass through
like with the original dermis. Silicon was then added to create a
protective top layer to represent the epidermis. This added layer
protected the new dermis as well as the inner fluids of the body. The
synthetic dermis allowed blood vessels to grow, but couldn’t produce
hair follicles or sweat glands.[4]
In the late 1970s, medical researchers began experimenting with
sheets of artificial skin that could be permanently grafted onto
patients who have no other options. Two Boston surgeons discovered a
successful new artificial skin design in 1981 that is known as Integra.
Instead of replicating the function of healthy skin, Integra “tricks”
real skin cells into growing a new dermis, which would replace the
damaged dermis.[5]
Progress
Research is continually being done on artificial skin. Typically, a
collagen scaffold is used (the
protein
that underlies the structure of skin), which can be additionally seeded
with patient's own cells,[6][7][8]
or with
foreskin from newborns that has been removed during
circumcision.The edges of the scaffold meet with the healthy skin,
allowing the new skin to heal quicker. Artificial skin can be used to
save patients who have lost more than 50% of their own skin to burns,
skin disorders, or certain forms of cancer.[9][10]
Additional technologies, such as an
autologous
spray-on skin produced by
Avita Medical,[11]
are being tested in efforts to accelerate
healing
and minimize scarring.
The
Fraunhofer Institute for Interfacial Engineering and Biotechnology
is working towards a fully
automated process for producing artificial skin. Their goal is a
simple two-layer skin without blood vessels that can be used to study
how skin interacts with consumer products, such as creams and medicines.
They hope to eventually produce more complex skin that can be used in
transplants.[12]
Hanna Wendt, and a team of her colleagues in the Department of
Plastic, Hand and Reconstructive Surgery at Medical School Hannover
Germany, have found a method for creating artificial skin using
spider silk. Before this, however, artificial skin was grown using
materials like
collagen. These materials did not seem strong enough. Instead, Wendt
and her team turned to spider silk, which is known to be 5 times
stronger than
Kevlar.
The silk is harvested by “milking” the silk glands of golden orb web
spiders. The silk was spooled as it was harvested, and then it was woven
into a rectangular steel frame. The steel frame was 0.7 mm thick and the
resulting weave was easy-to-handle, as well as easy to sterilize. Human
skin cells were added to the meshwork silk and were found to flourish
under an environment providing nutrients, warmth and air. However at
this time, using spider silk to grow artificial skin in mass quantities
is not practical because of the tedious process of harvesting spider
silk.[13]
Australian researchers are currently searching for a new, innovative
way to produce artificial skin. This would produce artificial skin
quicker, and in a more efficient way. The skin produced would only be 1
millimeter thick and would only be used to rebuild the epidermis. They
can also make the skin 1.5 millimeters thick, which would allow the
dermis to repair itself if needed. This would require
bone marrow from a donation or from the patient's body. The bone
marrow would be used as a “seed," and would be placed in the grafts to
mimic the dermis. This has been tested on animals and has been proven to
work with animal skin. Professor Maitz said, “In Australia, someone with
a full-thickness burn to up to 80 per cent of their body surface area
has every prospect of surviving the injury…However their quality of life
remains questionable as we're unable, at present, to replace the burned
skin with normal skin…We're committed to ensuring the pain of survival
is worth it, by developing a living skin equivalent.”[14]
Synthetic skin
Another form of “artificial skin” has been created out of flexible
semiconductor materials that can sense touch for those with
prosthetic limbs.[15][16]
The artificial skin is anticipated to augment
robotics in conducting rudimentary jobs that would be considered
delicate and require sensitive “touch”.[15][17]
Scientists found that by applying a layer of rubber with two parallel
electrodes that stored electrical charges inside of the artificial skin,
tiny amounts of pressure could be detected. When pressure is exerted,
the electrical charge in the rubber is changed and the change is
detected by the electrodes. However, the film is so small that when
pressure is applied to the skin, the molecules have nowhere to move and
become entangled. The molecules also fail to return to their original
shape when the pressure is removed.[18]
thumbnail
Artificial Microfluidic Skin for In Vitro Perspiration Simulation and
Testing
An artificial skin has also been recently demonstrated at the
University of Cincinnati for in-vitro sweat simulation and testing,
capable of skin-like texture, wetting, sweat pore-density, and sweat
rates. The sweat simulator employs a simple bi-layer membrane design to
resolve all drawbacks associated with use of commercial membranes. A
bottom 0.2 µm track etched polycarbonate membrane layer provides
flow-rate control by creating a pressure drop and therefore a constant
sweat flow. A top photo-curable layer provides skin-like features such
as sweat pore density, hydrophobicity, and wetting hysteresis. Key
capabilities of this sweat simulator include: constant ‘sweat’ rate
density without bubble-point variation even down to ~1 L/hr/m2;
replication of the 2 pores/mm2 pore-density and the ~50 µm texture of
human skin; simple gravity-fed flow control; low-cost and disposable
construction.[19]