ENGR0011 Schaub 4:00
Group R15
THE POTENTIAL BENEFITS OF USING CARBON NANOTUBES IN
NEURAL INTERFACING OUTWEIGH THE RISKS
Victor Hoang (vih10@pitt.edu)
INTRODUCTION: THE RISE OF
NANOTUBE USAGE IN NEUROSCIENCE
Carbon nanotubes – the do-it-all wonder child of
modern science – have long had a niche in a variety of
fields, from architecture to computer chip production.
Materials scientists have used these incredibly strong,
electrically conductive, hollow molecules of carbon for more
than a decade, adding them to batteries to increase durability
and creating light-emitting structures in telecommunications
[1]. In the past few years, major breakthroughs have been
made concerning carbon nanotube implementation in the
brain. Researchers at the University of Texas have
demonstrated that carbon nanotubes have the ability to
communicate electrical signals to neurons [1]. This suggests
that carbon nanotubes could potentially be used as an
electrical interface in neural prosthetics. If this is the case,
people suffering from nerve damage in the eye, brain, and
spinal cord could have a more effective and efficient option
in terms of neural prosthetic implants.
While there are inherent risks in experimenting
with a relatively new technology, it is my belief that the
potential benefits of using carbon nanotubes as a neural
interface outweigh those risks. The concern with nanotube
usage in the brain lies in the unpredictable nature of cellular
reactivity [5]. Although this is a legitimate concern, carbon
nanotubes offer promise and an alternative to patients
currently suffering due to inefficient neural prosthetic
devices [2]. As a future biomedical engineer, I recognize that
my job will be to one day improve patient care through
medical advances, as is detailed in the Biomedical
Engineering Society’s code of ethics. Along with
understanding the value of knowing the ethical implications
of nanotube use, it is important to understand the value of
writing a research-based position paper. Due to my research,
I believe that carbon nanotube use in neural interfacing is a
breakthrough technology that can benefit humanity.
AT THE NANOMOLECULAR LEVEL:
CARBON NANOTUBES AT A GLANCE
A carbon nanotube is a cylinder which has a wall of
single graphite atoms [4]. The strength of the nanotube lies
in its unique sp2 bonding structure, where each individual
carbon atom is bonded to three neighbors [3]. These carboncarbon bonds produce a tensile strength up to 63 GPa, which
is 50x higher than steel [5]. At certain pressures the atomic
bonding of the nanotube changes, allowing multiple
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nanotubes to link together to form a longer chain [4].
Therefore nanotubes are exceedingly strong yet still flexible.
The key characteristic of carbon nanotubes which makes
them useful in neural prosthetics is their minuscule size.
Nanotubes can be manufactured to scales thousands of times
smaller than most widely used neural prosthetic devices [2].
These characteristics all factor into the unexplored potential
that carbon nanotubes have in neuroscience.
A NEW OPTION: THE ROLE OF CARBON
NANOTUBES IN NEURAL PROSTHESES
Like the nervous cells of our brain, carbon
nanotubes are excellent electrical signal conductors [7]. This
means that the carbon nanotube has the ability to form
mechanical contacts with cellular membranes, which allows
it to act as a functional link to brain structures [7]. This is
important because it is a completely new way of
approaching neural prostheses.
The main problem with existing technologies in
neural prosthetics lies in the reactive cellular response
following insertion of a neural prosthetic device in the brain
[2]. The brain’s biological response is to release astrocytes
and microglial cells to insulate the prosthetic device and
shield the surrounding damaged tissue [2]. This ultimately
leads to device failure, because a long-term link with brain
structures cannot be established. Although testing is still in
the preliminary stages, researchers at the University of Texas
have found a possible solution to this problem through the
use of carbon nanotubes [1]. These researchers have found
that the surface of carbon nanotubes can be coated with
molecules that look friendly to brain cells [1]. Nicholas
Kotov, an associate professor of chemical engineering at the
University of Michigan, states “surface modifiers need to be
chosen so that the cell considers the nanotubes part of its
natural environment” [1]. New technologies are shifting
toward mimicking the natural function of the brain by
simulating the electrical properties of a neuron [6]. Because
carbon nanotubes have the capacity to transmit electrical
signals from neurons to the brain, they are an ideal electrical
interface for neural prostheses. Existing methods fail
because the cells in the brain treat prosthetic implants as
foreign entities; if carbon nanotubes can mimic actual cells,
more effective and longer lasting neural prosthetic devices
can be created.
Carbon nanotube implementation in the brain is an
innovative technology important for patient care. The
ultimate goal of biomedical engineering is improving the
quality of life for patients. Through my research of carbon
Victor Hoang
nanotube usage in neural prostheses, I have concluded that
the existing methods of neural prosthetic device
implementation are inefficient. There is no sense in
continuing the use of silicon devices, metal plating, or
surface-sensing electrodes – they are simply not effective
over a long period of time due to their reactivity with cells in
the brain. If my goal as a biomedical engineer is to improve
the experience of patients, I would want to create a neural
prosthetic device that functions as naturally as possible,
acting like a cluster of nerves. If there is even the slightest
possibility that that can be achieved through the use of
carbon nanotubes then I would commit to understanding and
using the new technology as soon as possible. At the same
time it would be irresponsible of me to ignore the potential
risks that are associated with carbon nanotubes.
Understanding the problems with a technology is just as
important as understanding the technology itself.
FINAL CONCERNS: ETHICAL
IMPLICATIONS OF NANOTUBE USE
As exciting as nanotube technology is, and as
tempting as it may be to push the boundaries of this medical
advancement, it is important to not lose sight of the code of
ethics that binds all professional engineers. As the first
fundamental canon of the National Society of Professional
Engineers’ Code of Ethics states, “Engineers shall hold
paramount the safety, health, and welfare of the public” [9].
Carbon nanotube use in neural interfacing is an incredibly
delicate process that requires implementation of an electrode
into the brain. There is no room for error in such a
procedure, as the lives of patients are at stake. A faulty
neural prosthetic device has an immediate and tangible
negative effect on the health of patients, which violates this
canon. Only through rigorous testing, data collection, and
device modification can biomedical engineers ensure that
carbon nanotube integration in neural prostheses will have
no negative effects on patients.
In terms of advancement in carbon nanotube
research, the Biomedical Engineering Society’s code of
ethics states that “biomedical engineers involved in health
care activities shall consider the broader consequences of
their work in regard to cost, availability, and delivery of
health care” [10]. Biomedical engineers should focus their
research on aspects of nanotube usage that can improve the
welfare of patients. The problem with research in a new
technology is investing resources into a variety of projects
simply for the sake of obtaining information. This is
inefficient because valuable time and money is wasted on
projects that make no difference in the healthcare of patients.
Focusing the bulk of nanotube research on projects that can
benefit patient care will result in the development of more
research projects that can potentially improve healthcare.
As a future biomedical engineer, I understand the
value of abiding by a code of ethics. It is critical to
understand that the engineering profession is a profession
that is dedicated to others. Only through the application of
an ethical code that is based on impartiality and integrity can
the best methods for improving patient care be utilized.
UNCERTAINTY IN NANOTECHNOLOGY:
RISKS OF NANOTUBE USAGE
The problem with carbon nanotube use is the same
problem faced with any relatively new technology – the
scarce availability of experimental data. Simple physics
states that as a particle shrinks, the ratio of its surface area to
its mass rises [5]. Therefore a nanoparticle has a
comparatively larger surface area which can lead to greater
reactivity. The concern that scientists have with inserting
carbon nanotubes into the brain is the unpredictable nature
of cellular reactions [1]. For example, a research experiment
headed by Chiu-Wing Lam at NASA’s Johnson Space
Center found that in the lungs of mice, carbon nanotubes
caused lesions that progressively worsened over time [5].
Another example lies in the field of bioimaging, where
nanoparticles known as “quantum dots” could potentially be
used to detect tumors [5]. However, the quantum dots are
typically made up of cadmium selenide, which can be toxic
in bulk quantities [5]. These examples illustrate the problem
with nanotube usage. There is a lack of reliable data, which
makes it difficult to discern whether an experimental result
is the norm or a fluke. Regulatory agencies suffer from the
same problem. The National Institute for Occupational
Safety and Health acknowledges that “minimal information”
is available on the health risks associated with nanomaterials
contact [5]. These factors combine to create an atmosphere
of uncertainty regarding nanotube usage in neural
interfacing. The potential benefits are clear, but the data is
lagging behind the technology.
While the concerns with nanotube usage are
legitimate, I believe that it is necessary to continue advanced
research in this technology. The potential benefits of carbon
nanotube usage in neuroscience could restore damaged
nerves and improve neural prosthetics. Even if it takes years
to understand the negative consequences, there is no doubt
that carbon nanotube technology can improve human lives.
REFLECTION: EDUCATIONAL VALUE OF
A RESEARCH-BASED POSITION PAPER
Research-based position papers have value in any
freshman engineering curriculum at any engineering school
in the country because students have the opportunity to
research topics that genuinely interest them. In a study done
at Vanderbilt University, Dr. Paul King found that research
projects in the freshman bioengineering curriculum led to
“increased retention and interest on the part of the students”
[11]. Interested, motivated students are more likely to
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immerse themselves into researching and developing their
own stance on a topic.
My personal experience with this research-based
position paper was very positive. I chose to research the role
of carbon nanotubes in neural interfacing because I had read
articles on the topic and found it to be interesting. After
researching the topic, I understood the potential benefits of
the technology and concluded that current neural prostheses
were ineffective and inefficient. Because of my genuine
interest, I reached out to a graduate professor here at the
university, Dr. Tracy Cui, who is researching the exact same
topic in her lab. After meeting with her one-on-one and
discussing the details of my position paper, she offered me a
research position in the university’s neural tissue
engineering lab. Because of my position paper, I went from
reading online articles about experiments involving carbon
nanotubes to actually encapsulating carbon nanotubes onto
gold-sputtered monomers myself in a state-of-the-art lab.
The position paper sparked my interest and led me to seek
out an opportunity where I could apply my knowledge.
Discussing the ethics of nanotube usage and
learning about the professional engineering code of ethics is
valuable knowledge as well. Understanding the guidelines
and ideals for my eventual profession and how they apply to
my research topics gives me the opportunity to better
appreciate the engineering profession.
hopes that creating a synthetic brain may one day be
possible [8]. These innovative medical breakthroughs are an
example of the type of work that can be accomplished by
well-educated engineers. Producing motivated engineers that
research topics that genuinely interest them leads to these
types of advances.
There are endless possibilities regarding carbon
nanotube usage in neuroscience. The potential to benefit
millions of lives is clear, and I believe that the only limiting
factor is the creativity of the human mind, not the lack of
experimental data. As long as the ethical implications of
nanotube technology are understood and the code of ethics is
followed, there is little reason to stop advancing nanotube
usage. Integrating carbon nanotubes into neural prostheses
could repair damaged optic nerves and damaged cochlear
nerves. Spinal cord paralysis patients could resume normal
lives through nerve repairs. All of this can potentially be
achieved through nanotube technology and that is why I
believe that the potential benefits of using carbon nanotubes
in neural interfacing outweigh the risks.
The only question I have is – how far can we go?
REFERENCES
[1] K, Bourzac. (2006). “This Is Your Brain on
Nanontubes.” Technology Review. (Online Article).
http://www.technologyreview.com/news/405853/this-is-youbrain-on-nanotubes/
[2] N, Tokas. (2010). “Carbon Nanotube-based Neural
Prosthetics – Where Smaller is Better.” Nanotech Now.
(Online Article). http://www.nanotechnow.com/columns/?article=460
[3] P, Harris. (2010). “Carbon nanotube science and
technology.” The University of Reading Personal Web
Pages. (Online Article).
http://www.personal.reading.ac.uk/~scsharip/tubes.htm#Hist
ory
[4] D, Memetic. (2010). “Nanotubes.” Tech FAQ. (Online
Article). http://www.tech-faq.com/nanotubes.html
[5] P, Ross. (2006). “Tiny Toxins?” Technology Review.
(Online Article).
http://www.technologyreview.com/featuredstory/405743/tiny-toxins/
[6] J, Laskaris. (2011). “An Emerging Tool in
Neuroscience.” MD Buyline. (Online Article).
http://www.mdbuyline.com/an-emerging-tool-inneuroscience
[7] M, Berger. (2012). “Carbon nanotube rope stimulates
neural stem cells.” Nano Werk. (Online Article).
http://www.nanowerk.com/spotlight/spotid=26029.php
[8] E, Mankin. (2011). “Functioning Synapse Created Using
Carbon Nanotubes.” Neuroscience News. (Online Article).
http://neurosciencenews.com/synapse-using-carbonnanotubes-synthetic-brain/
CONCLUSION: THE FUTURE OF CARBON
NANOTUBE USAGE
More than 5 million Americans live with
disabilities resulting from a traumatic brain injury [2].
Neurodegeneration in the brain can lead to severe motor
conditions from loss of limb control to complete paralysis
[2]. Nerve damage correction has been attempted for
decades through the implementation of neural prosthetic
devices. Recent technological advances in the field have
shown that carbon nanotubes can be used in neural
interfacing to create more efficient and longer lasting
prosthetic devices. The main problem with the nanotube
technology is the lack of experimental data available. As a
future biomedical engineer, I believe that it is crucial to
utilize this technology to improve patient care. While it is
important to understand the risks involved with nanotube
implementation, it is equally important to push the
boundaries of this exciting breakthrough.
Already scientists have found that carbon
nanotubes can be used as a scaffold to physically repair
damaged nerves [6]. Thomas Webster, an associate professor
of materials science and biomedical engineering at Brown
University, has demonstrated that carbon nanotubes help
stem cells stay in place after they are injected into damaged
brain cells [1]. Engineering researchers at the University of
Southern California have built a carbon nanotube synapse
circuit which can reproduce the function of a neuron, raising
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Victor Hoang
[9] (2012). “NSPE Code of Ethics for Engineers.” National
Society of Professional Engineers. (Online Article).
http://www.nspe.org/Ethics/CodeofEthics/index.html
[10] (2012). “Biomedical Engineering Society Code of
Ethics.” Biomedical Engineering Society. (Online Article).
http://www.bmes.org/aws/BMES/pt/sp/ethics
[11] P, King. (2002). “Freshman Biomedical Engineering
Design Projects: What Can Be Done?” American Society for
Engineering Education. (Online Article).
http://www.vanth.org/docs/005_2002.pdf
ACKNOWLEDGEMENTS
I would like to thank the University of Pittsburgh
for having no classes on Monday, October 8th so that I could
write my paper. I would also like to thank Cheese for
sharing his Doritos with me. Finally, I would like to shout
out my roommate Chris for editing my paper.
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