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 Researchers uncover protein-based “cancer signature”
05.12.2016 | Universität Basel

nachricht The Nagoya Protocol Creates Disadvantages for Many Countries when Applied to Microorganisms
05.12.2016 | Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

IHP presents the fastest silicon-based transistor in the world

05.12.2016 | Power and Electrical Engineering

InLight study: insights into chemical processes using light

05.12.2016 | Materials Sciences

High-precision magnetic field sensing

05.12.2016 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>