A Better Artificial Skin
Skin cells genetically engineered to be resistant to bacteria could reduce infections and improve the chances of survival among burn victims.
A patient’s skin cells, genetically modified and grown in a test tube, could provide the next generation of artificial skin. As a first step in creating such replacement skin, scientists in Cincinnati have engineered bacteria-resistant skin cells in the lab and are now testing them in animals. Ultimately, they hope to produce a type of artificial skin that can sweat, tan, and fight off infection.
“We’re using genetic modification to try to get the cultured skin to behave more like normal skin,” says Dorothy Supp, a researcher at the Cincinnati Shriners Hospital for Children who led the project.
Skin keeps us hydrated, cools us with sweat, and forms a blockade against foreign bacteria. Without skin’s protective covering, victims of severe burns suffer serious dehydration and are vulnerable to life-threatening bacterial infections. Grafts of healthy skin on the injured areas can help, but people with large burns often don’t have enough healthy skin to graft.
Over the past decade, artificial-skin products–made from scaffolds of collagen, the molecule that gives skin its structure and elasticity–have drastically improved burn victims’ chances of survival. Large sheets of the flexible mesh placed over open wounds encourage the growth of new dermis, the bottom layer of skin, which does not regenerate under normal circumstances. Surgeons can then transplant small pieces of the patient’s epidermis, the top layer of skin, which grows and spreads over the newly grown dermis.
More recently, scientists have begun seeding the collagen scaffolds with skin cells to help the skin grow: rather than transplanting epidermis onto the newly grown skin, scientists grow epidermis cells on the collagen scaffold and then transplant the entire sheet. In an experimental method developed by Steven Boyce of the University of Cincinnati, a patient’s own skin cells are biopsied and then grown in culture. The cells attach to a collagen scaffold, forming a skin-like structure and generating sheets up to 100 times the size of the original biopsy.
One of the remaining major problems with artificial skin is its vulnerability infection. It can take a week or two for blood vessels, which carry the immune system’s infection-fighting machinery, to connect to the newly growing dermis. “Without blood vessels, bacteria can grow and cause infection, and may destroy the graft and open the wound once more,” says Ioannis Yannas, a bioengineer and materials scientist at MIT who helped develop the first artificial-skin product. Currently, doctors must continually wrap wounds with antibacterial bandages.
So Supp and colleagues genetically modified skin cells to produce higher levels of an antibacterial protein. In a paper published in the current issue of the Journal of Burn Care and Research, Supp showed that these skin cells, when grown in a test tube, could kill more of a specific kind of bacteria than standard skin cells.
Supp cautions that the engineered cells are still a long way from clinical use. The true test of the bacteria-fighting properties will come in the complex environment of a real wound, which is littered with many different types of bacteria. The researchers are now planning experiments in animal models.
Ideally, Supp wants to create even better-cultured skin, with cells that can grow the molecular structures required to produce sweat, hair, and pigment. “If we can start with two cell types and add one or two genes at a time and get these structures to develop, that would be very exciting,” she says.
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. It has been developed commercially under the name IntegraTM and is used in massively burned patients, during plastic surgery of the skin, and in the treatment of chronic skin wounds.
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).
Synthetic skin
Another form of “artificial skin” has been created out of flexible semiconductor materials that can sense touch for those with prosthetic limbs. The artificial skin is anticipated to augment robotics in conducting rudimentary jobs that would be considered delicate and require sensitive “touch”. 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. A recent development in the synthetic skin technique has been made by imparting the colour 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, colour to be reflected by the skin can be controlled. This technology can be used in colour-shifting camouflages and sensors that can detect otherwise imperceptible defects in buildings, bridges, and aircraft.
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