Hybrid Tunnel

May Help Severed nerves Guide Back to Health :

Building a tunnel formed by two hard and soft materials to guide the re-connection of severed nerves can be the first step to help patients who have suffered extensive nerve trauma recover feeling and movement, according to a team biomedical engineering.
"Damage to the nerves in both the central nervous system and peripheral nervous system is a major health problem," said Mohammad Reza Abidian, assistant professor of biomedical engineering, Penn State. "According to the National Spinal Cord Injury Statistical Center, there are approximately 290,000 people in the U.S. who suffer from spinal cord injuries, with about 12,000 new injuries occurring each year."
Spontaneous nerve regeneration is limited to small injuries peripheral nervous system injury and actively suppressed in the central nervous system. When a nerve in the peripheral nervous system is a bit short, nerves can regenerate and reconnect. However, if the distance between the two is too late, growth can deviate and fail to connect.
The researchers, who published their findings in the current issue of the health of Advanced Materials, developed a new hybrid line consists of a soft material called hydro-gel, as an outside wall next to an interior wall made of an electrically active polymer conducting serve to guide tunnel regeneration and re-connection of severed nerve endings.
Abidian says the method may offer advantages over current surgeries used to reconnect severed nerves.
"Autografts are currently the gold standard value to close the gaps," said Abidian. "This is an operation that takes the nerve from another part of the body - for example - of a tendon, and then grafted into the injured nerve."

However, the operation can be painful and often there are mismatches in size between severed nerve endings and the new grafted nerve, Abidian said.
The researchers used arose  a hydro-gel is permeable and more likely to be accepted by the body. However, because the hydro-gel expands in water and liquid from the expansion and collapse of the tunnel to reduce the capacity of regeneration of the nerve endings and connecting said Abidian. A second pattern is created by adding a conductive polymer, poly (3.4-ethylene dioxythiophene) - PEDOT - the design to form a wall that can mechanically support and reinforce the hydrogel. PEDOT is a stable material that can conduct electricity to aid electrical signals pass through the nerve.
To ensure nutrients and oxygen reach the nerve endings of regeneration, the team created a spiral PEDOT maintaining the structural integrity of the wall, but allowed some nutrients and air to reach the nerve.
The researchers tested the three designs - friction hydrogel, hydrogel wall completely covered PEDOT and PEDOT hydrogel wall partially covered - for device implantation in 10 mm nerve gaps in rats and measurement of muscle mass and muscle strength in late contractions nerves. These measurements can indicate whether the nerve has reconnected separated.
They also analyzed the optical images of cross sections of nerves to assess their relative health.
According Abidian, PEDOT spiral design generated significantly greater muscle mass than other designs, but not enough to generate muscle autograft is used as control in the study design.
The photographs of the spiral design PEDOT showed that health of the nerve itself was almost indistinguishable from a nerve photographed after autograft operation.
Abidian said the next step will be to secure funding to test the design when the spaces between the severed nerves are so great that even autograft operations are ineffective. He said he hoped that the design can be used to create other types of medical implants such as neural interfaces.
"This design shows that, yes, it can work," said Abidian. "But now we have to see if the electrical impulses and chemicals can pass through the gaps much more to guide and modulate axonal regeneration."
Abidian worked with Eugene Daneshvar, a graduate student in biomedical engineering; Brent Egeland, surgical resident in plastic surgery, Daryl Kipke, a professor of biomedical engineering, principal investigator in the Laboratory of Neural Engineering and director of the Center for Neural Communication Technology,Cederna Paul, section chief of plastic surgery and associate director of the department of surgery and Melanie Urbanchek, research assistant professor of plastic surgery section, all of the University of Michigan