May 172010
== Summary == author: Nuno Nogueira
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A new approach to tiny fuel cells implanted in rats enables the devices to generate electricity for months using sugar in the rodents’ bodies

The advent of the artificial heart has spurred scientists to pursue synthetic kidneys and pancreases as well. Still, one key obstacle to realizing such devices is powering them after they have been implanted. Instead of having to constantly recharge them by hooking them up to some external system—or, worse, periodically removing them and replacing their batteries—researchers would prefer that these machines somehow harvest energy from their hosts.

Now there is hope that future implants might be powered not by batteries but by the fuels in our bodies that are used for energy. Scientists have shown that fuel cells implanted in rats can successfully generate electricity from sugar in the rodent’s bodies. The devices kept going for months at a time.

The most potent sugar-powered fuel cells to date, so-called glucose biofuel cells, rely on enzymes that harvest electricity from chemical reactions—for instance, the combination of glucose with oxygen, both available in the human (and rat) body. Compounds dubbed “redox mediators” then act like wires, transporting electric charge from these enzymes to electrodes that lead from the fuel cell to whatever device it is powering. Scientists are currently pursuing a variety of such devices to generate electricity in an environmentally friendly manner.

Unfortunately, the enzymes used in past glucose biofuel cells were not suitable for implants, because they either required highly acidic conditions to work or were inhibited by a variety of ions found in the body. The newly developed devices lack these constraints and are the first functional implantable glucose biofuel cells, with prototypes in rats stably generating power for at least three months.

“It becomes possible to envisage development of implantable robots capable of compensating for failing functions in human beings,” says researcher Philippe Cinquin, a biomedical engineer at Université Joseph Fourier in Grenoble, France.

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