The miniaturization of electrical sensors coupled with the development of flexible silicon technology paves the way for a wide variety of medical sensors that can be implanted into the human body. One of the major obstacles facing the development of such devices, not to mention artificial organs, is how they are powered. Currently devices need to be constantly recharged via an external power source or, as is the case with battery-powered pacemakers, replaced altogether. Now a team of French researchers has implanted a new type of biofuel cell into rats that overcomes these problems by generating electricity from a potentially limitless source - sugar in the rat’s bodies.

The new type of Glucose BioFuel Cell (GBFC) developed by a team from Joseph Fourier University in Grenoble, France, headed by Philippe Cinquin, harvests energy from glucose and oxygen in the body using enzymes. Glucose and oxygen flows into the device and enzymes catalyze the oxidation of glucose to generate electricity. The electric charges is then transported from these enzymes via compounds dubbed “redox mediators” to electrodes that lead from the biofuel cell to the device it is powering.

Previous attempts at developing such implants have failed either because the enzymes require highly acidic conditions to work, or were inhibited by charged particles of chlorine, or urate anions, present in the fluid surrounding the cells. To overcome these problems Cinquin and his team confined glucose enzymes inside graphite discs that were placed into dialysis bags, which use plastics already clinically approved for implants.

The fuel cells were surgically implanted into the abdominal cavity of two rats and were able to produce a peak power of 6.5 microwatts. Technology Review reports that the power remained around two microwatts for a period of 11 days in one rat, and the other rat showed byproducts of glucose oxidation in its urine for three months, indicating the device lasts at least that long.

Pacemakers require 10 microwatts, but the team’s prototype fuel cell’s two electrodes took up just 0.266 milliliters of the 5-milliliter fuel cell. So in principle a milliliter’s worth of these electrodes could generate a peak power level of 24.4 microwatts. Cinquin and his team also believe they can improve efficiency of the fuel cells. "I'm optimistic that we will get tens of milliwatts in future versions," he said.

The team’s findings appear in a paper entitled, “A Glucose BioFuel Cell Implanted in Rats,” published in the journal PLoS ONE.

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