IEEE Spectrum November, 2014 - 62

lEt thEM SEE
YoU SWEat
continued from page 50

Compared with ions and metabolites,

many of the biomarkers that doctors rely
on for diagnosis of stress, disease, poor
nutrition, injury, and other conditions
are far harder to detect because they
are found in blood and sweat in mere
nanomolar to picomolar concentrations
(a mere billionth or trillionth by weight).
But detecting their presence in sweat is
nevertheless possible.
Lately, some of the hardest-to-measure
biomarkers-small-protein cytokines-
are generating the most excitement.
Cells release cytokines under a number of circumstances, including trauma,
infection, and cancer. For example, the
concentration of a cytokine called interleukin 6 (IL-6) can increase up to a thousandfold during an infection.
Esther Sternberg and her colleagues
at the University of Arizona recently
demonstrated that several cytokines,

including IL-6, have the same concentration in sweat as they do in blood. This
means doctors could use sweat to diagnose a wide variety of physical and mental stresses. Right now, though, the tools
needed to measure the nanomolar to
picomolar concentrations of cytokines
in sweat are as big as a refrigerator, or
at best a suitcase. The trick here is getting the technology down to the size of
a wearable gadget. My colleagues and
I think that's possible and are working
toward that goal.
The basic problem is this: These biomarkers are present at such low concentrations that they can't generate enough
voltage or current themselves to overcome noise. A better strategy would be
to coat an electrode with a biorecognition element-basically a biochemical
puzzle piece custom designed to selectively match up to, grab, and hold the biomarker we are trying to sense. We would
then apply an alternating electrical signal
to the electrode. As biomarkers gather on
the electrode, they should act as a barrier

to electrical current, increasing the electrical impedance in a measurable way.
A more exotic and sensitive approach
would be to add a molecule called a
redox couple to the top of the biorecognition element. A redox couple inserted
in an electrochemical process makes
it easier for electrons to move from
a solution to an electrode. When the
biomarker binds to the biorecognition
element, it changes the shape of the element, bringing the redox couple closer
to the electrode, close enough to allow
it to dramatically increase the flow of
current. With support from the National
Science Foundation and a biochemist
in my lab, we recently demonstrated
sensing cytokines down to a level of less
than a 1-picomolar concentration using
this technique.
The Air Force is interested in the possibility of measuring cytokine biomarkers to monitor extreme stresses on pilots.
And it is even more interested in neuropeptide biomarkers that can give clues
to the state of the brain, like one called

invites you to where academia and industry meet ...
IEEE CCECE 2015
Canadian Conference on

IEEE IHTC 2015

Electrical and Computer
Engineering
Celebrating 30 Years of
Ocean Frontiers

International
Humanitarian Technology

Electrical
Power and Energy

Supporting Communities
Towards Resilience

Platinum Sponsor - London Hydro

Conference

Smarter Resilient Power Systems

Photo: Tourism London

Photo: Ottawa Convention Centre

Photo: HPA/Nova Scotia Tourism

Halifax, Nova Scotia, Canada

Ottawa, Ontario, Canada

London, Ontario, Canada

Call for Papers and Panels

Call for Papers and Industry Panels

May 3-6, 2015

IEEE EPEC 2015

May 31-June 4, 2015

October 26-28, 2015

http://ccece2015.org

http://ihtc.ieee.ca

http://epec2015.ieee.ca

Tweet us... @CCECE2015

Tweet us... @IEEE-IHTC

Tweet us... @EPEC2015

nov 2014

north american

SPectrUm.ieee.orG

http://www.ccece2015.org http://epec2015.ieee.ca http://ihtc.ieee.ca http://SPectrUm.ieee.orG

Table of Contents for the Digital Edition of IEEE Spectrum November, 2014