Laccase Inhibition by Arsenite/Arsenate: Determination of Inhibition Mechanism and Preliminary Application to a Self-Powered Biosensor

The reversible inhibition of laccase by arsenite (As3+) and arsenate (As5+) is reported for the first time. Oxygen-reducing laccase bioelectrodes were found to be inhibited by both arsenic species for direct electron-transfer bioelectrodes (using anthracene functionalities for enzymatic orientation) and for mediated electron-transfer bioelectrodes [using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as an electron mediator]. Both arsenic species were determined to behave via a mixed inhibition model (behaving closely to that of uncompetitive inhibitors) when evaluated spectrophotometrically using ABTS as the electron donor. Finally, laccase bioelectrodes were employed within an enzymatic fuel cell, yielding a self-powered biosensor for arsenite and arsenate. This conceptual self-powered arsenic biosensor demonstrated limits of detection (LODs) of 13 mu M for arsenite and 132 mu M for arsenate. Further, this device possessed sensitivities of 0.91 +/- 0.07 mV/mM for arsenite and 0.98 +/- 0.02 mV/mM for arsenate.