"A bioelectric battery can be implanted into the human body and relies on oxygen in the internal body fluid to produce electrical energy. In this work, a battery that uses polypyrrole doped with a biological polyelectrolyte (dextran sulfate, an anti-coagulant) as the cathode and bioresorbable Mg alloy (AZ61) as the anode was developed. This battery exhibited a discharge capacity of 565 mA h g(-1) in phosphate buffered saline (PBS, pH = 7.4), a commonly used electrolyte in biological research; offering a specific energy density of similar to 790W h kg(-1). The electrochemical properties of the cathode, anode and battery itself were investigated in different aqueous electrolytes. Cyclic voltammetry, linear sweep voltammetry, AC impedance, galvanostatic charge/discharge, and field-emission scanning microscopy techniques were applied for characterization. (C) 2012 Elsevier B.V. All rights reserved."