Awhile ago on the show I mentioned a bit about bioelectrodes made from enzyme-coated nanotubes. Here’s the paper that was published on it:

http://www.nature.com/ncomms/journal/v2/n6/full/ncomms1365.html?WT.ec_id=NCOMMS-20110628

What I found really cool was that it provided a way to tap into the metabolic energy of a cell and turn it into electricity. Normally in biotic systems metabolism has to cycle in coenzymes like NAD+ (nicotinamide adenine dinucleotide) and move protons and their bond electrons through a complex electron transport chain to get usable energy out of the breakdown of glucose. These bioelectrodes allow you to directly harvest electricity from a catabolic reation. It had a very good efficiency as well – the voltage measured across the electrodes was nearly identical to the redox potential of the enzyme. There is very little energy being lost by transducing energy using this method.