This paper details the development of a mitochondria-based biofuel cell. We show that mitochondria can be immobilized at a carbon electrode surface and remain intact and viable. The electrode-bound mitochondria drive complete oxidation of pyruvate as shown by Carbon-13 NMR and serve as the anode of the biofuel cell where they convert the chemical energy in a biofuel (such as pyruvate) into electrical energy. These are the first organelle-based fuel cells. Researchers have previously used isolated enzymes and complete microbes for fuel cells, but this is the first evidence that organelles can Support fuel Cell-based energy conversion. These biofuel cells provide power densities of 0.203 +/- 0.014 mW/cm(2). which is in between the latest immobilized enzyme-based biofuel cells and microbial biofuel cells. while providing the efficiency of microbial biofuel cells. (c) 2008 Elsevier Ltd. All rights reserved.