Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Polymers promote nerve regeneration

13.02.2003


Ames Laboratory researcher’s microscale channels steer neurons to rewire damaged nerves



Using microscale channels cut in an ultrathin biodegradable polymer, a researcher at the U.S. Department of Energy’s Ames Laboratory is working to regrow nerve cells. The technique, which may one day allow the paralyzed to walk and the blind to see, has been proven to work for peripheral nerve regeneration in laboratory rats.

Nerve cells are unlike most other biological tissue. When a nerve is severed, the part of the neuron "downstream" of the injury typically dies off. And neurons in the human body can be several feet long. Grafting, which works well for other tissue such as skin, isn’t the best option because of loss of nerve function where the donor tissue is removed and the difficulty in getting the nerve cells to line up and reconnect.


"Nerve cells aren’t able to easily bridge gaps of more than one centimeter," says Surya Mallapragada, an Ames Laboratory associate in Materials Chemistry and a chemical engineering professor at Iowa State University. "Peripheral nervous system (PNS) axons – the part of the nerve cell which carries the impulses – normally have a connective tissue sheath of myelin guide their growth, and without that guidance, they aren’t able grow productively."

Since the nervous system carries electrical impulses, it helps to think of nerve cells in terms of electrical wiring. Bundles of nerves are like an electrical cable with multiple wires. When a nerve "cable" is cut and cells die, it would be as though the copper wire downstream of the damage disappeared, leaving only the empty plastic insulation tubes. In order for new copper wiring to push out across the gap and fill in the empty insulation tubes, you’d need a way to guide the wires into the empty insulation. And that’s where Mallapragada’s research comes in.

By working on a cellular scale, she has developed a way to help guide neurons so they grow in the right direction. Starting with biodegradable polymer films only a few hundred microns thick (100 microns equals 0.004 in. – significantly less than the thickness of a human hair), Mallapragada and her colleagues have developed methods for making minute patterns on these incredibly thin materials.

"We’ve made grooves three to four microns deep to help channel nerve cell growth," Mallapragada said. "The grooves have a protein coating and we’ve also ’seeded’ them with Schwann cells to help promote this growth." Schwann cells naturally form the myelin sheath around the PNS cells. When guided by this sheath, nerves will grow at a rate of three to four millimeters per day.

The polymers, primarily poly(lactide-co-glycolide) and polyanhydrides, degrade when exposed to water, and Mallapragada has worked to develop thin film polymers that bulk degrade in layers over a period of time ranging from a few days to almost a year.

To put the microscale grooves in the polymers, she has used both laser etching and reactive ion etching, relying on the Ames Lab’s Environmental and Protection Sciences Program and the Microanalytical Instrumentation Center’s Carver and Keck Laboratories and for the necessary equipment and expertise. After promising in vitro tests, Mallapragada worked with collaborators at Iowa State University’s College of Veterinary Medicine to conduct trials on rats. Small segments of the rats’ sciatic nerves, which deliver nerve messages to the hind legs, were removed and the severed nerves "spliced" using the polymer film. Though initially unable to use their legs, the rats started to regain use of their legs after three weeks and were able to function normally after six weeks.

Although the technique has shown great promise with PNS cell growth, getting similar results with the central nervous system, which includes the brain, spinal cord and optic nerve, is another matter. CNS cells grow differently than peripheral nerves, presenting special problems. Oligodendrocytes, the connective tissue of the CNS, can actually inhibit nerve growth.

Mallapragada has focused the next phase of her research on the optic nerve to try to better understand how CNS neurons work and grow.

"There are other factors at work, such as chemical and electrical cues," Mallapragada said. "Other researchers have had some success injecting adult (rat) stem cells into the site of the damaged optic nerve. Our hope is to eventually develop arrays of microelectrodes that will allow us to interface the optic nerve with a retinal chip … a bioartificial optic nerve, if you will."

The retinal chip, first developed at Johns Hopkins University, uses chip technology to replace the eye’s rods and cones. The technology transfers the digital images to the optic nerve via electrodes, but is limited by the inability to create electrodes that are small enough and numerous enough to create a resolution sufficient for the brain to decipher the input as it does with normal "sight."

"This research is a strong step forward in our basic understanding of nerve cell growth and how to engineer materials that help the body repair itself," said Ari Patrinos, Director of the Office of Biological and Environmental Research. "We hope the groundwork laid by Ames Laboratory will soon pave the way for human subjects to benefit from this technology."


Mallapragada was honored for this and related polymer research in 2002 by being named one of the world’s top 100 young innovators by Technology Review, a technology magazine published the Massachusetts Institute of Technology. She is also associate director of the Microanalytical Instrumentation Center at Iowa State University.

The research was funded by the DOE Office of Science’s Office of Biological and Environmental Research; and the National Science Foundation. Ames Laboratory is operated for the DOE by Iowa State University. The Lab conducts research into various areas of national concern, including energy resources, high-speed computer design, environmental cleanup and restoration, and the synthesis and study of new materials.

Surya Mallapragada | EurekAlert!
Further information:
http://www.external.ameslab.gov/

More articles from Life Sciences:

nachricht Solving the efficiency of Gram-negative bacteria
22.03.2019 | Harvard University

nachricht Bacteria bide their time when antibiotics attack
22.03.2019 | Rice University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The taming of the light screw

DESY and MPSD scientists create high-order harmonics from solids with controlled polarization states, taking advantage of both crystal symmetry and attosecond electronic dynamics. The newly demonstrated technique might find intriguing applications in petahertz electronics and for spectroscopic studies of novel quantum materials.

The nonlinear process of high-order harmonic generation (HHG) in gases is one of the cornerstones of attosecond science (an attosecond is a billionth of a...

Im Focus: Magnetic micro-boats

Nano- and microtechnology are promising candidates not only for medical applications such as drug delivery but also for the creation of little robots or flexible integrated sensors. Scientists from the Max Planck Institute for Polymer Research (MPI-P) have created magnetic microparticles, with a newly developed method, that could pave the way for building micro-motors or guiding drugs in the human body to a target, like a tumor. The preparation of such structures as well as their remote-control can be regulated using magnetic fields and therefore can find application in an array of domains.

The magnetic properties of a material control how this material responds to the presence of a magnetic field. Iron oxide is the main component of rust but also...

Im Focus: Self-healing coating made of corn starch makes small scratches disappear through heat

Due to the special arrangement of its molecules, a new coating made of corn starch is able to repair small scratches by itself through heat: The cross-linking via ring-shaped molecules makes the material mobile, so that it compensates for the scratches and these disappear again.

Superficial micro-scratches on the car body or on other high-gloss surfaces are harmless, but annoying. Especially in the luxury segment such surfaces are...

Im Focus: Stellar cartography

The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.

A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...

Im Focus: Heading towards a tsunami of light

Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.

"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

International Modelica Conference with 330 visitors from 21 countries at OTH Regensburg

11.03.2019 | Event News

Selection Completed: 580 Young Scientists from 88 Countries at the Lindau Nobel Laureate Meeting

01.03.2019 | Event News

LightMAT 2019 – 3rd International Conference on Light Materials – Science and Technology

28.02.2019 | Event News

 
Latest News

Solving the efficiency of Gram-negative bacteria

22.03.2019 | Life Sciences

Bacteria bide their time when antibiotics attack

22.03.2019 | Life Sciences

Open source software helps researchers extract key insights from huge sensor datasets

22.03.2019 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>