Wiring the Brain at the Nanoscale

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july 7, 2005

Wiring the Brain at the Nanoscale

Nanowires in blood vessels may help monitor, stimulate neurons in the

brain

http://www.nsf.gov/news/news_summ.jsp?cntn_id=104288 & org=NSF & from=news

Working with platinum nanowires 100 times thinner than a human

hair--and using blood vessels as conduits to guide the wires--a team

of U.S. and Japanese researchers has demonstrated a technique that may

one day allow doctors to monitor individual brain cells and perhaps

provide new treatments for neurological diseases such as Parkinson's.

Writing in the July 5, 2005, online issue of The Journal of

Nanoparticle Research, the researchers explain it is becoming feasible

to create nanowires far thinner than even the tiniest capillary

vessels. That means nanowires could, in principle, be threaded through

the circulatory system to any point in the body without blocking the

normal flow of blood or interfering with the exchange of gasses and

nutrients through the blood-vessel walls.

The team describes a proof-of-principle experiment in which they first

guided platinum nanowires into the vascular system of tissue samples,

and then successfully used the wires to detect the activity of

individual neurons lying adjacent to the blood vessels.

Rodolfo R. Llinás of the New York University School of Medicine led

the team, which included Kerry D. Walton, also of the NYU medical

school; Masayuki Nakao of the University of Tokyo; and Ian Hunter and

A. Anquetil of the Massachusetts Institute of Technology.

" Nanotechnology is becoming one of the brightest stars in the medical

and cognitive sciences, " said Mike Roco, Senior Advisor for

Nanotechnology at the National Science Foundation (NSF), which funded

the research.

Already, the researchers note, physicians routinely use arterial

pathways to guide much larger catheter tubes to specific points in the

body. This technique is frequently used to study blood flow around the

heart, for example.

Following the same logic, the researchers envision connecting an

entire array of nanowires to a catheter tube that could then be guided

through the circulatory system to the brain. Once there, the wires

would spread into a " bouquet, " branching out into tinier and tinier

blood vessels until they reached specific locations. Each nanowire

would then be used to record the electrical activity of a single nerve

cell or small groups of them.

If the technique works, the researchers say, it would be a boon to

scientists who study brain function. Current technologies, such as

positron emission tomography (PET) scans and functional magnetic

resonance imaging (fMRI), have revealed a great deal about how neural

circuits process, say, visual information or language. But the view is

still comparatively fuzzy and crude. By providing information on the

scale of individual nerve cells, or " neurons, " the nanowire technique

could bring the picture into much sharper focus.

" In this case, we see the first-ever application of nanotechnology to

understanding the brain at the neuron-to-neuron interaction level with

a non-intrusive, biocompatible and biodegradable nano-probe, " said

Roco. " With careful attention to ethical issues, it promises entirely

new areas of study, and ultimately could lead to new therapies and new

ways of treating diseases. This illustrates the new generations of

nanoscale active devices and complex nanosystems. "

Likewise, the nanowire technique could greatly improve doctors'

ability to pinpoint damage from injury and stroke, localize the cause

of seizures, and detect the presence of tumors and other brain

abnormalities. Better still, Llinás and his coauthors point out, the

nanowires could deliver electrical impulses as well as receive them.

So the technique has potential as a treatment for Parkinson's and

similar diseases.

According to researchers, it's long been known that people with

Parkinson's disease can experience significant improvement from direct

stimulation of the affected area of the brain. Indeed, that is now a

common treatment for patients who do not respond to medication. But

the stimulation is currently carried out by inserting wires through

the skull and into the brain, a process that can cause scarring of the

brain tissue. The hope is, by stimulating the brain with nanowires

threaded through pre-existing blood vessels, doctors could give

patients the benefits of the treatment without the damaging side effects.

One challenge is to precisely guide the nanowire probes to a

predetermined spot through the thousands of branches in the brain's

vascular system. One promising solution, the authors say, is to

replace the platinum nanowires with new conducting polymer nanowires.

Not only do the polymers conduct electrical impulses, conductive, they

change shape in response to electric fields, which would allow the

researchers to steer the nanowires through the brain's circulatory

system. Polymer nanowires have the added benefit of being 20 to 30

times smaller than the platinum ones used in the reported laboratory

experiments. They also will be biodegradable, and therefore suitable

for short-term brain implants.

" This new class of materials is an attractive tool for

nanotechnology, " said MIT's Anquetil. " The large degrees of freedom

that they offer synthetically allow the rational design of their

properties. "

-NSF-