Fig. 2.

Optical and electrochemical metrics of the Ir-reducing capacity assay. (a) A redox-mediator (K₂IrCl₆, Ir^OX) is used to detect oxidative stress by probing the reducing capacities of a diluted serum sample. During a 1 h incubation, Ir^OX is converted to Ir^Red by accepting electrons from the sample's reductants. Independent measures of the residual Ir^OX are obtained optically (Abs at 490 nm) and electrochemically (reductive charge; Q.RED), while measures of the generated Ir^Red are obtained electrochemically (oxidative charge; Q.OX). (b) For the electrochemical measurement, three sequential electrical input voltages are imposed: (i) E1 is a 2-min imposed oxidation voltage (+0.7 V vs Ag/AgCl) that yields one metric (the cumulative oxidative charge during these 2 min; Q.OX); (ii) E2 is a 2-min imposed reduction voltage (+0.1 V vs Ag/AgCl) that yields a second metric (the cumulative reductive charge during these 2 min; Q.RED); and (iii) E3 is a 10-min imposed cyclic voltage (CV) that generates 2 additional metrics (Q.CV1 and Q.CV3) that reflect the dynamic balance between the reduction of the residual Ir^OX and oxidation of the generated Ir^Red. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)