Using SERS Sensitive Reaction Strategy To Detect Superoxide Anion Radical

Superoxide radical(O₂^·-)is a kind of substance obtained by oxygen reduction under the condition of single electron.The increase of O₂^·-will lead to changes in the double-stranded structure of DNA,resulting in gene mutations,and then produce tumors(the average concentration of O₂^·-in normal blood is 3.0μmol/L).Therefore,the monitoring and evaluation of O₂^·-in organism is particularly important.Due to the relatively short survival time of O₂^·-,currently only electron paramagnetic resonance（EPR）method can be used for direct detection.However,EPR instrument is not only very expensive,but also difficult to operate,so it is not suitable for routine analysis.The commonly used detection methods include electrochemical method,fluorescence method and bioluminescence protein method,but the electrochemical method needs to construct a more complex sensor,and the selectivity is not high.Fluorescence method is usually photobleaching and sensitive.The linearity of bioluminescence protein method is narrow,and the sensitivity is generally not high.Surface Enhanced Raman Scattering Spectroscopy（SERS）technology is often used in the trace detection of biomarkers because of its fast,sensitive,safe,and nondestructive detection.Most of the commonly used SERS substrates are gold（Au）or silver（Ag）nanosols synthesized by hydrothermal method.They show strong hydrophilicity and have good enhancement effect on hydrophilic substances,so they can be used for direct or indirect detection of trace biomarkers.O₂^·-itself does not have Raman scattering,in this thesis,2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-a]pyrazine-3-one（CLA）chemiluminescence reagent was made from SERS probe,CLA can react with O₂^·-particularity to generate two oxygen ethane analogues（herculean task）,through the change of the signal,thereby realizing methods used in SERS indirectly,rapid,and sensitive detection of target objects.The main research contents are as follows:1.Because CLA has good water solubility,CLA can be modified on the surface of gold nanoparticles.In this work,the SERS probe molecules of Au NPs/CLA were formed by mixing CLA and Au NPs solution evenly.The linear range was 50 μmol/L—50 nmol/L,and the linear relationship was good（R²=0.9868）.The limit of detection was 9.0 nmol/L,and the sensitivity was high.At the same time,the limit of detection of O₂^·-produced by UV irradiation in Ti O₂ in sunscreen is 72.8 nmol/L.2.Intracellular O₂^·-level is associated with many diseases.It has been reported in relevant literature that O₂^·-level in cancer cells presents a tendency of high expression.Due to the interfering substance inside the cell is more,in order to reduce the influence of interfering substance,and the work was synthesized liposome wrapped Au NPs/used CLA of SERS nano reaction system,used in the detection of intracellular O₂^·-,liposome used package of SERS probe can reduce cytotoxicity,also can improve the selectivity of probe molecules,but also increased the enrichment effect of O₂^·-,for later detection in the cell concentration of O₂^·-laid a solid foundation.The SERS nanometer reaction system wrapped by liposomes showed good linearity in the concentration range of 20μmol/L—50 nmol/L,R²=0.9904,the limit of detection was 9.85 nmol/L,and the sensitivity was high.