The Study Of Superoxide Anion Radical Released From Cell Based On Polyamidoamine And Metal Nanoparticles Modified Electrode

Speroxide anion（O₂·^-）is one of the most important oxygen species（ROS）in organisms,its dynamic release process from living cells could provide abundant physiological and pathological information.Hence,evaluating dynamic changes of O₂·^-concentration is of great significance in cells.Poly（amidoamine）（PAMAM）dendrimers have been widely used in electrochemical sensor due to its unique properties,such as controllable surface functionality,internal void space,hydrophilicity and controllable size.Metal nanoparticles have become excellent substitutes for enzymes due to their relatively high chemical catalytic properties,large specific surface area and high surface energy.This dissertation focused on the study of the nonenzyme superoxide anion sensors based on utilizing PAMAM as the matrix for supporting metal nanoparticles（NPs）.The main contents were summarized as follows:1.In this chapter,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·^-released 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 2.53×10^–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 A was chosen as the stimulant to induce cancer cells（rat adrenal medulla pheochromocytoma cell（PC12））to generate O₂·^-.The electrochemical experiment results indicated that the levels of intracellular O₂·^-depended on the amount of Zymosan A.More importantly,the electrochemistry 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.2.From the first chapter,we found that the structure of PAMAM could avoid the aggregation of metal nanoparticles effectively.However,the higher surface energy of AgNPs would seriously affect the conductivity.In this chapter,AuNPs and PAMAM were combined skillfully by a simple one-step reaction to immobilize on the electrode.Transmission electron microscopy（TEM）investigations for the PAMAM-Au nanocomposites indicate that large amounts of small-sized Au nanoparticles were encapsulated into interior of the dendrimers.The electrochemical experimental results demonstrated that this sensor exhibited excellent detection capability for O₂·^-,and a wide linear range from 3.69×10^-11to 3.72×10^-5M was obtained with a limit of detection（LOD）of 0.0123 nM.Moreover,we further explored the effect of environment temperature on U87 cells and SOD enzyme.