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 (O 2 • − ) sensor was constructed based on Ag nanoparticles (NPs) / poly (amidoamine) (PAMAM) dendrimers and used to investigate the dynamic process of O 2 • − 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 O 2 • − with a super low detection limit (LOD) of 2.530 × 10 –13   M (S/N = 3) and wide linear range of 8 orders of magnitude. It could fulfill the requirement of real-time measurement O 2 • − released from living cells. Furthermore, zymosan was chosen as the stimulant to induce O 2 • − generation from cancer cells (rat adrenal medulla pheochromocytoma cell (PC12)). The electrochemical experiment results indicated that the levels of intracellular O 2 • − depended on the amount of Zymosan. A large amount of O 2 • − 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 O 2 • − concentration at a normal physiological range. These findings are of great significance for evaluating the metabolic processes of O 2 • − in the biological system, and this work has the tremendous potential application in clinical diagnostics to assess oxidative stress .