The detection of O₂^•− is based on amperometry comprising of counter electrode and working electrodes. The counter electrode is a platinum plate (2.5×2.5mm) while the working electrodes (φ1mm) is an iron-porphyrin modified carbon electrode. Ag/AgCl was used as a reference electrode. The iron-porphyrin modified carbon electrode acts as O₂^•−detection sensor (Fig. 1).

The O₂^•− generation was measured in THP-1 cells (cell lines of myeloid leukemia patients) under the effect of differentiation inducer phorbol 12-myristate 13-acetate (PMA) in the absence and presence of exogenous addition 0.1 wt% Triton X at 25°C at a cell density of 3.0 × 10⁶ cells/well. Triton X is known to permeabilize the membranes of living cells. The results obtained showed no considerable changes in reduction currents for O₂^•− under the effect of inducer (PMA). However, the addition of Triton-X showed a fast increase in oxidation current for O₂^•− by about approximately 2 nA followed by a gradual drop which continued for a time span of more than 3 hours. We further investigated the effects of inhibitors for the activity of NADPH oxidase that catalytically produce ROS; apocynin were selected as inhibitors of NADPH oxidase [2].

The production of O₂^•−of real-time monitoring of NADPH oxidase inhibitory effect of PMA induced THP-1 cells using iron-porphyrin modified carbon electrode were detected by amperometory. The results shown in Fig.2 suggests that amperometory is mainly derived from the O₂^•−,whose expression is induced by NADPH oxidase.

[1] M. Yuasa et al. Polym. Adv. Technol. 16 (2005)287–292.

[2] S.Kasai et al. Analytica Chimica Acta 549 (2005)14-19.