Engineers from the Massachusetts Institute of Technology have developed
an implantable fuel cell that generates power through glucose oxidation, which
could help patients who are paralyzed and amputees move their arms and legs
again, according to a recent paper published by PLoS One.
“As implantable electronic devices become increasingly prevalent in
the diagnosis, management and treatment of human disease, there is a
correspondingly increasing demand for devices with unlimited functional
lifetimes that integrate seamlessly into their host biological systems,”
the researchers wrote. “In particular, micropower implantable electronics
beg the question of whether such electronics can be powered from their
surrounding tissues.”
The glucose fuel cell
The glucose fuel cell was first discovered in the 1970s when scientists
utilized enzymes to run a glucose fuel cell to power a pacemaker. However, the
idea of using a glucose fuel cell was abandoned for lithium-ion batteries
because they could provide more power.
“[The glucose fuel cell has] been the holy grail of medical devices
for a long time, but nobody could run it off such low power,” Rahul
Sarpeshkar, PhD, associate professor of electrical engineering at the
Massachusetts Institute of Technology, told O&P Business News.
Sarpeshkar and colleagues chose a different route to power the glucose
fuel cell. The team spent years working on cochlear implant and brain machine
interfaces for human applications — such as for deafness, blindness and
paralysis — that ran on ultra-low-power. With this background they were
motivated to fabricate a silicon chip that had no biological components but
mimicked the activity of cellular enzymes through a roughened platinum catalyst
that strips electrons from glucose.
“As a loose analogy to our work, a cleverly fabricated solar panel,
even if it is not the world’s best, can be combined with an
ultra-low-power car to make an interesting overall transportation solution that
no one else may have imagined possible,” Sarpeshkar said. “You need
the ultra-low-power car with the solar panel to create a car that functions
solely on solar energy harvested from one’s surroundings. You need the
ultra-low-power electronics and the glucose fuel cell to create a brain-machine
interface that functions on energy harvested from its surroundings. One
innovation alone is not enough to make an overall system that is useful.”
Once the idea was there, Sarpeshkar and colleagues needed to find the
best environment to implant the chip. They determined cerebrospinal fluid
— virtually acellular, under minimal immune surveillance with a
hundred-fold lower protein content and glucose levels comparable to blood and
other tissue — to be a promising environment for an implantable fuel cell.
“Cerebrospinal fluid is a particularly nice place to implant our
glucose fuel cell due to its low cellular and protein content — which can
cause biofouling in some implants — and because of its relatively good
glucose content,” Sarpeshkar said. “So that’s like running the
car on a road where there is good sunlight and not too many potholes that could
eventually wreck the car.”
The next step
Sarpeshkar and colleagues will need to test the glucose fuel cell in
animals before it can go through FDA trials.
“This is still years away from being an implantable medical device
that is approved by the FDA,” Sarpeshkar said. “I don’t think
it’s too far in the future, but it’s not going to be in people for at
least another 5 to 10 years.”
“[The glucose fuel cell] might open people’s eyes a little bit
into thinking about different power sources rather than just using a battery or
an inductive power coil. In general, it’s about designing smaller, lower
power, higher performance medical devices that run seamlessly with their
environments and with a lifetime supply of energy, so you never have to do
re-surgery to replace the battery and the patient doesn’t have to
constantly wear an external coil that powers an ultra capacitor implanted
inside them,” he said. — by Casey Murphy
References:
Rapoport BI. A glucose fuel cell for implantable brain-machine
interfaces. PLoS One. 2012;doi:10.1371/journal.pone.0038436.
Disclosure: Sarpeshkar has no relevant financial disclosures.