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Artificial Skin =LINK=



Skin substitutes have been a topic of study since the 15th century BC. Experts found the first written report of the skin xenograft (which is skin from animals) in a document called the Papyrus of Ebers. The use of a human skin allograft (skin from another human donor) was first described in 1503. Today, experts still use similar technologies in medical centers around the world.




artificial skin


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Experts have worked for about 2 decades to create skin-like circuits, or pieces of fake skin that can act like real skin. They can bend, twist, and stretch, then bounce back to their regular form, similar to how your skin keeps its form.


Single-layer durable skin substitutes. These are made from collagen sheets or other products. They can replace the outer layer of the skin or the thick layer just underneath it (epidermis and dermis). The collagen these are made from can come from cows, pigs, or even humans.


Composite skin substitutes. These are artificial skin options from either skin grafts or lab-made tissue. They also include allografts (tissue from another human) and xenografts (tissue from animals).


Zhenan Bao, PhD, a chemical engineer at Stanford University, and her research team studied printable versions of artificial skin. They created a way to print stretchy and strong pieces of skin-like material. This process uses the same tools used to make solid silicon chips.


Because the process is already in place for silicon chips, Bao and her team believe this can lead to mass production of artificial skin. Factories that make these chips can switch from solid materials to rubbery ones.


Artificial skin is a collagen scaffold that induces regeneration of skin in mammals such as humans. The term was used in the late 1970s and early 1980s to describe a new treatment for massive burns. It was later discovered that treatment of deep skin wounds in adult animals and humans with this scaffold induces regeneration of the dermis.[1] It has been developed commercially under the name Integra and is used in massively burned patients, during plastic surgery of the skin, and in treatment of chronic skin wounds.[2]


Alternatively, the term "artificial skin" sometimes is used to refer to skin-like tissue grown in a laboratory, although this technology is still quite a way away from being viable for use in the medical field. 'Artificial skin' can also refer to flexible semiconductor materials that can sense touch for those with prosthetic limbs (also experimental).


The skin is the largest organ in the human body.[3] Skin is made up of three layers, the epidermis, dermis and the fat layer, also called the hypodermis. 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.[4] 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 from the patient (autografts) or from an unrelated donor or a 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 had been damaged extensively, making it impossible to treat severely injured patients with autografts only.[5]


A process for inducing regeneration in skin was invented by Dr. Ioannis V. Yannas (then an assistant professor in the Fibers and Polymers Division, Department of Mechanical Engineering, at Massachusetts Institute of Technology) and Dr. John F. Burke (then chief of staff at Shriners Burns Institute in Boston, Massachusetts). Their initial objective was to discover a wound cover that would protect severe skin wounds from infection by accelerating wound closure. Several kinds of grafts made of synthetic and natural polymers were prepared and tested in a guinea pig animal model. By the late 1970s it was evident that the original objective was not reached. Instead, these experimental grafts typically did not affect the speed of wound closure. In one case, however, a particular type of collagen graft led to significant delay of wound closure.[6] Careful study of histology samples revealed that grafts that delayed wound closure induced the synthesis of new dermis de novo at the injury site, instead of forming scar, which is the normal outcome of the spontaneous wound healing response. This was the first demonstration of regeneration of a tissue (dermis) that does not regenerate by itself in the adult mammal.[7][8][9][10][11][12] After the initial discovery, further research led to the composition and fabrication of grafts that were evaluated in clinical trials.[11][13] These grafts were synthesized as a graft copolymer of microfibrillar type I collagen and a glycosaminoglycan, chondroitin-6-sulfate, fabricated into porous sheets by freeze-drying, and then cross-linked by dehydrothermal treatment.[14] Control of the structural features of the collagen scaffold (average pore size, degradation rate and surface chemistry) was eventually found to be a critical prerequisite for its unusual biological activity. In 1981 Burke and Yannas proved that their artificial skin worked on patients with 50 to 90 percent burns, vastly improving the chances of recovery and improved quality of life.[15][16] John F. Burke also claimed, in 1981, "[The Artificial skin] is soft and pliable, not stiff and hard, unlike other substances used to cover burned-off skin."[17]


Several patents were granted to MIT for the creation of collagen-based grafts that can induce dermis regeneration. U.S. Patent 4,418,691 (December 6, 1983) was cited by the National Inventors Hall of Fame as the key patent describing the invention of a process for regenerated skin (Inductees Natl. Inventors Hall of Fame, 2015[18]). These patents were later translated into a commercial product by Integra LifeSciences Corp., a company founded in 1989.[19] Integra Dermal Regeneration Template received FDA approval in 1996, and the FDA listed it as a "Significant Medical Device Breakthrough" in the same year.[20] Since then, it has been applied worldwide to treat patients who are in need of new skin to treat massive burns[21] and traumatic skin wounds,[22] those undergoing plastic surgery of the skin,[23] as well as others who have certain forms of skin cancer.[24]


In clinical practice, a thin graft sheet manufactured from the active collagen scaffold is placed on the injury site, which is then covered with a thin sheet of silicone elastomer that protects the wound site from bacterial infection and dehydration. The graft can be seeded with autologous cells (keratinocytes) in order to accelerate wound closure, however the presence of these cells is not required for regenerating the dermis.[10] Grafting skin wounds with Integra leads to the synthesis of normal vascularized and innervated dermis de novo, followed by re-epithelization and formation of epidermis. Although early versions of the scaffold were not capable of regenerating hair follicles and sweat glands, later developments by S.T Boyce and coworkers led to solution of this problem.[25]


Research is continually being done on artificial skin. Newer technologies, such as an autologous spray-on skin produced by Avita Medical,[29] 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.[30]


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 or 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.[31]


Another form of "artificial skin" has been created out of flexible semiconductor materials that can sense touch for those with prosthetic limbs.[33][34] The artificial skin is anticipated to augment robotics in conducting rudimentary jobs that would be considered delicate and require sensitive "touch".[33][35] 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.[36] A recent development in the synthetic skin technique has been made by imparting the color changing properties to the thin layer of silicon with the help of artificial ridges which reflect a very specific wavelength of light. By tuning the spaces between these ridges, color to be reflected by the skin can be controlled.[37] This technology can be used in color-shifting camouflages and sensors that can detect otherwise imperceptible defects in buildings, bridges, and aircraft. 041b061a72


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