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Researchers Pinpoint Neural Nanoblockers in Carbon Nanotubes
August 28, 2009A team of Brown University scientists has pinpointed why carbon nanotubes tend to block a critical signaling pathway in neurons. It's not the tubes, the team finds, but the metal catalysts used to form the tubes. The discovery means carbon nanotubes without metal catalysts may be useful in treating human neurological disorders. Results appear in Biomaterials.
PROVIDENCE, R.I. [Brown University] - Carbon nanotubes hold many exciting possibilities, some of them in the realm of the human nervous system. Recent research has shown that carbon nanotubes may help regrow nerve tissue or ferry drugs used to repair damaged neurons associated with disorders such as epilepsy, Parkinson's disease and perhaps even paralysis.
Yet some studies have shown that carbon nanotubes appear to interfere with a critical signaling transaction in neurons, throwing doubt on the tubes' value in treating neurological disorders. No one knew why the tubes were causing a problem.
Now a team of Brown University researchers has found that it's not the tubes that are to blame. Writing in the journal Biomaterials, the scientists report that the metal catalysts used to form the tubes are the culprits, and that minute amounts of one metal - yttrium - could impede neuronal activity. The findings mean that carbon nanotubes without metal catalysts may be able to treat human neurological disorders, although other possible biological effects still need to be studied.
"We can purify the nanotubes by removing the metals," said Lorin Jakubek, a Ph.D. candidate in biomedical engineering and lead author of the paper, "so, it's a problem we can fix."
Jakubek took single-walled carbon nanotubes to the laboratory of Diane Lipscombe, a Brown neuroscientist. The researchers zeroed in on ion channels located at the end of neurons' axons. These channels are gateways of sorts, driven by changes in the voltage across neurons' membranes. When an electrical signal, known as an action potential, is triggered in neurons, these ion channels "open," each designed to take in a certain ion. One such ion channel passes only calcium, a protein that is critical for transmitter release and thus for neurons to communicate with each other.
In experiments using cloned calcium ion channels in embryonic kidney cells, the scientists discovered that nickel and yttrium, two metal catalysts used to form the single-walled carbon nanotubes, were interfering with the ion channel's ability to absorb the calcium.
Because its ionic radius is nearly identical to calcium's, yttrium in particular "gets stuck and prevents calcium from entering and passing through. It's an ion pore blocker," said Lipscombe, who specializes in neuronal ion channels and is a corresponding author on the paper.
The experiments showed that yttrium in trace amounts - less than 1 microgram per milliliter of water - may disrupt normal calcium signaling in neurons and other electrically active cells, an amount far lower than what had been thought to be safe levels. With nickel, the amount needed to impede calcium signaling was 300 times higher.
"Yttrium is so potent that ... a very low nanotube dose" would be needed to affect neuronal activity, said Robert Hurt, professor of engineering and a corresponding author on the paper.
Jakubek said she was surprised that the metals turned out to be the cause. "Based on the literature, I thought it would be the nanotubes themselves," she said.
Spiro Marangoudakis, Jessica Raingo and Xinyuan Liu contributed to the paper. The National Institutes of Health, the National Science Foundation and the U.S. Environmental Protection Agency funded the research.
Brown University
Now a team of Brown University researchers has found that it's not the tubes that are to blame. Writing in the journal Biomaterials, the scientists report that the metal catalysts used to form the tubes are the culprits, and that minute amounts of one metal - yttrium - could impede neuronal activity. The findings mean that carbon nanotubes without metal catalysts may be able to treat human neurological disorders, although other possible biological effects still need to be studied.
"We can purify the nanotubes by removing the metals," said Lorin Jakubek, a Ph.D. candidate in biomedical engineering and lead author of the paper, "so, it's a problem we can fix."
Jakubek took single-walled carbon nanotubes to the laboratory of Diane Lipscombe, a Brown neuroscientist. The researchers zeroed in on ion channels located at the end of neurons' axons. These channels are gateways of sorts, driven by changes in the voltage across neurons' membranes. When an electrical signal, known as an action potential, is triggered in neurons, these ion channels "open," each designed to take in a certain ion. One such ion channel passes only calcium, a protein that is critical for transmitter release and thus for neurons to communicate with each other.
In experiments using cloned calcium ion channels in embryonic kidney cells, the scientists discovered that nickel and yttrium, two metal catalysts used to form the single-walled carbon nanotubes, were interfering with the ion channel's ability to absorb the calcium.
Because its ionic radius is nearly identical to calcium's, yttrium in particular "gets stuck and prevents calcium from entering and passing through. It's an ion pore blocker," said Lipscombe, who specializes in neuronal ion channels and is a corresponding author on the paper.
The experiments showed that yttrium in trace amounts - less than 1 microgram per milliliter of water - may disrupt normal calcium signaling in neurons and other electrically active cells, an amount far lower than what had been thought to be safe levels. With nickel, the amount needed to impede calcium signaling was 300 times higher.
"Yttrium is so potent that ... a very low nanotube dose" would be needed to affect neuronal activity, said Robert Hurt, professor of engineering and a corresponding author on the paper.
Jakubek said she was surprised that the metals turned out to be the cause. "Based on the literature, I thought it would be the nanotubes themselves," she said.
Spiro Marangoudakis, Jessica Raingo and Xinyuan Liu contributed to the paper. The National Institutes of Health, the National Science Foundation and the U.S. Environmental Protection Agency funded the research.
Brown University
Carbon Nanotubes Current Events and Carbon Nanotubes News RSSCaltech scientists develop DNA origami nanoscale breadboards for carbon nanotube circuits
In work that someday may lead to the development of novel types of nanoscale electronic devices, an interdisciplinary team of researchers at the California Institute of Technology (Caltech) has combined DNA's talent for self-assembly with the remarkable electronic properties of carbon nanotubes, thereby suggesting a solution to the long-standing problem of organizing carbon nanotubes into nanoscale electronic circuits.
Breakthrough in industrial-scale nanotube processing
Rice University scientists today unveiled a method for the industrial-scale processing of pure carbon-nanotube fibers that could lead to revolutionary advances in materials science, power distribution and nanoelectronics.
Next-generation microcapsules deliver 'chemicals on demand'
Scientists in California are reporting development of a new generation of the microcapsules used in carbon-free copy paper, in which capsules burst and release ink with pressure from a pen.
Study shows how carbon nanotubes can affect lining of the lungs
Carbon nanotubes are being considered for use in everything from sports equipment to medical applications, but a great deal remains unknown about whether these materials cause respiratory or other health problems.
Advance in 'nano-agriculture': Tiny stuff has huge effect on plant growth
With potential adverse health and environmental effects often in the news about nanotechnology, scientists in Arkansas are reporting that carbon nanotubes (CNTs) could have beneficial effects in agriculture.
A recipe for controlling carbon nanotubes
Nanoscopic tubes made of a lattice of carbon just a single atom deep hold promise for delivering medicines directly to a tumor, sensors so keen they detect the arrival or departure of a single electron, a replacement for costly platinum in fuel cells or as energy‐saving transistors and wires.
Friction force differences could offer a new means for sorting and assembling nanotubes
Nanotubes and nanowires are promising building blocks for future integrated nanoelectronic and photonic circuits, nanosensors, interconnects and electro-mechanical nanodevices. But some fundamental issues remain to be resolved - among them, how to position and manipulate the tiny tubes.
New biosensor can detect bacteria instantaneously
A research group from the Rovira i Virgili University (URV) in Tarragona has developed a biosensor that can immediately detect very low levels of Salmonella typhi, the bacteria that causes typhoid fever.
Researchers design new graphene-based, nano-material with magnetic properties
An international team of researchers has designed a new graphite-based, magnetic nano-material that acts as a semiconductor and could help material scientists create the next generation of electronic devices like microchips.
Pitt researchers harness carbon nanomaterials for drug delivery systems, oxygen sensors
Two nanoscale devices recently reported by University of Pittsburgh researchers in two separate journals harness the potential of carbon nanomaterials to enhance technologies for drug or imaging agent delivery and energy storage systems, in one case, and, in the other, bolster the sensitivity of oxygen sensors essential in confined settings, from mines to spacecrafts.
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