Construction And Performance Study Of A Novel Superoxide Anion Electrochemical Sensor Based On Mn-SOD Mimic Enzyme

Reactive oxygen species（ROS）are important intracellular signaling molecules,mainly regulating DNA damage,protein synthesis,cell apoptosis,etc.However,the excessive amount of ROS accumulation in cells will lead to oxidative stress that causes various pathological events such as neurodegeneration,alzheimer disease,autoimmune diseases and cancer.Therefore,the selective and accurate measure of ROS are important to illuminate the mechanism of regulating signal transduction pathways and further exploit the potential application in clinical pathological diagnosis.Among various ROS,the superoxide anion radical(O₂^·-)is the most active one and involves in many physiological and pathological processes.The relationship between O₂^·-concentration and human health has attracted great attention.Therefore,it is very necessary to detect O₂^·-in vivo.The electrochemical sensors have been widely used in biological monitoring,food analysis,environment protection,clinical research and other fields due to theirsimple preparation,easy operation,fast response and low cost.The simulated enzyme overcomes the disadvantages of high cost,easy inactivation and difficult extraction of natural enzyme.In this dissertation,several O₂^·-electrochemical sensors based on simulated enzymes and nanomaterials are constructed.The details are as follows:1)A O₂^·-electrochemical sensors was fabricated by immobilizing gold nanoparticles（AuNPs）and Mn-cysteine（Mn-cys）onto the glassy carbon electrode（GCE）surface.Mn-Cys was synthesized by manganese sulfate and L-cysteine.Under the optimum conditions,the modified electrode in the testing process can obviously distinguish the reduction peak positions of O₂ with-0.3 V and H₂O₂ with-0.66 V due to the catalysis of Mn-Cys.The sensor has a sensitivity of 1.81×10³μA·mM^-1·cm^-2and a detection limit of1.27μM（S/N=3）.2)A O₂^·-electrochemical sensors was fabricated by immobilizing electrochemical reduction of graphene oxide（ERGO）and manganese porphyrin（MnTPPCL）onto the GCE surface.Simultaneous existence of MnTPPCL and ERGO showed good catalytic performance toward the electrochemical reduction of O₂^·-,the reducing potential of O₂^·-was-0.3 V.Under the optimum experimental conditions,the sensor showed good selectivity,reproducibility and stability with the sensitivity of 22.2μA·m M^-1·cm^-2 and the detection limit was 3.97μM（S/N=3）.3)A O₂^·-electrochemical sensors was fabricated by immobilizing multiwalled carbon nanotubes（MWCNTs）and macrocyclic complexes of manganese（Mn-APB）onto the glassy carbon electrode（GCE）surface.The sensor showed good catalytic performance toward the electrochemical reduction of O₂^·-due to the synergistic effect of Mn-APB and MWCNTs.The preparation conditions and detection conditions of the electrode were optimized by experiments.Under the optimum conditions,the prepared sensor has good analytical performance with the sensitivity of 140μA·mM^-1·cm^-2and the detection limit of3.75μM（S/N=3）.In addition,the prepared sensor has good selectivity,reproducibility and stability.