The toxicity-related current changes, i.e., “true” signals, can be calculated by subtracting the ΔI values measured during the abiotic control experiments ( Fig. S4) from those measured during the Cu(II)-challenge tests operated in the CP mode ( Fig. 3). It is important to note that Oprozomib no similar subtraction/correction can be done for the sensors operated in the ER mode because of the varying anode potentials. The toxicity-related ΔI, in general, followed a similar trend to the total ΔI (toxicity plus electrodeposition). It increased as the anode potential increased from −0.41 V to −0.1 V but then decreased as the anode potential further increased to 0.1 V ( Fig. 6). The toxicity-related ΔI values at low CPs (?−0.1 V) were found to be consistent with purine predicted by a kinetic model developed by Stein et al. (2011) for heavy-metal toxicity MFC sensors. The decrease in the toxicity-related ΔI at high anode potentials could be related to the occurrence of power overshoots.