Neural Probe Developed That Will Limit Damage To Cells And Biological Tissue

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Neural Probe Developed That Will Limit Damage To Cells And Biological

Tissue

http://medicalnewscenter.com/out/out.cgi?

http://www.sciencedaily.com/releases/2008/10/081015164334.htm

Engineering researchers at the University of Arkansas have developed

a neural probe that demonstrates significantly greater electrical

charge storage capacity than all other neural prosthetic devices.

More charge storage capacity means the device can stimulate nerves

and tissues with less damage and sense neural signals with better

sensitivity.

Findings of the project were published in Nanotechnology 2008 and

will be included in an upcoming issue of IEEE Transactions on

Biomedical Engineering.

The neural probe, made of gold and iridium oxide nanowires grown

vertically on a polymer or titanium substrate, will improve the

function and reliability of neural prosthetic devices. It has also

displayed superior biocompatibility and mechanical strength compared

to similar silicon structures.

" Our goal is to develop functional systems that can simultaneously

stimulate nerves or muscle cells and record physiological changes in

the human body, " said Hargsoon Yoon, research assistant professor in

the College of Engineering and lead researcher on the project. " Our

approach can minimize cell damage and even provide higher electrode

efficiency than commonly used electrodes. "

Needle probes are used as neural prostheses to help improve quality

of life for patients with severe impairments. Current clinical

applications of neural prosthetics include cochlear and retinal

implants, cardiac pacing and defibrillation, restoration of urinary

bladder function, functional electrical stimulation in paralyzed

individuals and deep brain stimulation for people with Parkinson's

disease and Tourette syndrome.

The research team, based at the university's Center for Wireless Nano-

, Bio- and Info-Tech Sensor and Systems, developed probes that

integrate free-standing, " hetero-structured " nanowires. Hetero-

structured means the nanowires have an inner core and outer layer.

Made of gold, the inner-core nanowires were grown vertically on

titanium and polymer substrates. The outer, functional layer, made of

iridium oxide, provides charge storage capacity for neural signal

sensing and stimulation.

Researchers repeatedly demonstrated an electrical storage capacity of

48.6 Coulombs per square centimeter. Units of electrical charge are

measured in Coulombs. Working with different materials, other major

research groups, including teams at Stanford University and

University of Southern California, have developed probes with less

than half the storage capacity of the University of Arkansas probe.

Because storage capacity is directly related to density of electrical

current needed to stimulate nerves and muscle cells, the probe can

transfer charge into biological cells and tissues using less voltage –

and less battery power – and thus can operate longer with less

tissue and cell damage.

" Electrodes with low-charge storage capacity require higher

stimulating voltage levels, " Yoon said. " It is this higher voltage

that can damage biological tissues and the electrode itself. "

Yoon collaborates with Vijay Varadan, distinguished professor of

electrical engineering and director of the university's High Density

Electronics Center, to develop a system that will include nanowire

electrodes, wireless communication and a power source for bio-

packaging. The wireless network will facilitate closed-loop dynamic

adjustments of the system and continuous monitoring of patients

during stimulation.

Varadan holds the College of Engineering's Twenty-First Century

Endowed Chair in Nano- and Bio-Technologies and Medicine and the

college's Chair in Microelectronics and High Density Electronics. In

addition to his position as director of the above center, he directs

the university's High Density Electronics Center. Varadan is also a

professor of neurosurgery in the College of Medicine at the

University of Arkansas for Medical Sciences in Little Rock, Ark.