We learned in introductory biology classes that mitochondria are the power plants of cells. A simple concept like this can be easily taken for granted, but chemists like Saint Louis University professor Shelley Minteer see creative applications. She proposed that mitochondria can be incorporated into a biofuel cell to make devices such as self-powered sensors for explosives.



Depictions of mitochondria.

Minteer and her colleagues immobilized intact mitochondria on carbon anodes. Cellular mitochondria are capable of oxidizing "fuels" such as pyruvate to produce energy, so the mitochondria on the anode should catalyze this reaction when pyruvate is present in the biofuel cell solution. The oxidation leads to a transfer of electrons to the electrode, producing power to turn on the sensor, leading to a positive signal.

Since pyruvate is in the fuel cell solution, one would expect a positive signal all the time. However, mitochondria naturally have many inhibitors that prevent them from processing biofuels. Oligomycin is one such inhibitor that shuts down power production—conveniently, nitroaromatics, common explosive materials, reverse this inhibition. Thus, by adding the inhibitor to a biofuel cell, a sensor is created, as significant power production will only occur when enough explosive chemicals are present to release the inhibition.

Minteer's sensor was able to detect explosives present in concentrations as low as one picomolar. In the presence of nitroaromatics, the sensor showed a 40-fold increase in power density compared to the inhibited state. The signal for the presence of explosives is no different if the concentration is 1 picomolar or 1 millimolar, so it only works as a threshold sensor, providing just a on or off signal. Minteer hopes that further engineering will allow concentration-specific detection, as well.

Minteer's research team successfully demonstrated that the unique properties of mitochondria have applications far outside of biology. She predicts that a mitochondria-catalyzed biofuel cell can "be used as a traditional electrochemical sensor or in the self-powered sensor design."

J. Am. Chem. Soc., 2008. DOI: 10.1021/ja807250b