Construction of an ultrasensitive non-enzymatic sensor to investigate the dynamic process of superoxide anion release from living cells.

In this work, a novel non-enzymatic superoxide anion (O2•-) sensor was constructed based on Ag nanoparticles (NPs) / poly (amidoamine) (PAMAM) dendrimers and used to investigate the dynamic process of O2•- release from living cells. The AgNPs/PAMAM nanohybrids were characterized by transmission electron microscopy (TEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The fabricated electrode exhibited excellent catalytic activity toward the reaction of O2•- with a super low detection limit (LOD) of 2.530 × 10-13M (S/N = 3) and wide linear range of 8 orders of magnitude. It could fulfill the requirement of real-time measurement O2•- released from living cells. Furthermore, zymosan was chosen as the stimulant to induce O2•- generation from cancer cells (rat adrenal medulla pheochromocytoma cell (PC12)). The electrochemical experiment results indicated that the levels of intracellular O2•- depended on the amount of Zymosan. A large amount of O2•- generated in the living cells by added heavy stimulant could damage cells seriously. More importantly, a vitro simulation experiment confirmed the role of superoxide dismutase (SOD) for the first time because it could maintain the O2•- concentration at a normal physiological range. These findings are of great significance for evaluating the metabolic processes of O2•- in the biological system, and this work has the tremendous potential application in clinical diagnostics to assess oxidative stress.