A Metabolic Biofuel Cell: Conversion of Human Leukocyte Metabolic Activity to Electrical Currents

Presently, there are few options for supplying power to implantable medical devices. The ultimate goal of this preliminary work is to develop an implantable biofuel cell device that may be used within the physiological environment for low-power implantable medical device applications (such as miniature biosensors) [1-3]. A biofuel cell (BFC) is an electrochemical or galvanic device that couples the oxidation of a biofuel (such as glucose) at the anode to the reduction of molecular oxygen to water at the cathode. Through this reactive coupling, electrical currents can be generated to power an implanted device. With the movement of electrons through the circuit from the anode to the cathode through the device, it is necessary to also have the simultaneous movement of positive charge between the two electrodes to satisfy the requirements of a closed circuit. This positive charge takes the form of protons that travel from the anode through an electrolyte to the cathode where water is the final byproduct.Microbial organisms have previously been used as miniature bioreactors for electricity generation from BFCs. The microbes metabolize a substrate (such as glucose or acetate) and subsequently transfer high energy electrons to the anode of the BFC [4-14]. Electrons derived from these biofuels are subsequently transferred to the anode across the plasma membrane of the cells, while protons are also simultaneously released by the cells into the extracellular space. In another type of BFC - referred to here as an enzymatic biofuel cell (EnzBFC) for differentiation - specific enzymes are immobilized at the anode and cathode [15-21]. At the anode, glucose oxidase may be used to oxidize glucose to gluconolactone, while a laccase enzyme or bilirubin oxidase may be tethered to the cathode surface to reduce oxygen to water.Electron transfer between cellular metabolic processes and electrodes has previously only been observed for microbes confined to the anode of a biofuel cell (BFC)