Research On Enzyme-like Activity Of Au Nps And Construction Of Glucose Oxidase Mimic With Substrate-selectivity

Since the the enzyme-like activity of Fe3O4 nanoparticles was brought forward by Xiyun Yan,over forty kinds of nanomaterials have been found to possess enzyme-like activities.The enzyme-like activities of nanomaterials have become an international research hotspot,and been applied in biomedicine,environmental protection,industrial manufacture and many other aspects.Gold nanoparticles(AuNPs)with oxidase-like,peroxidase-like catalase-like and superoxide dismutase-like activities exhibit competitive research and application potential due to the multiple catalytic activities The improvement of the catalytic activity and substrate-selectivity is the key point and bottleneck in the research of enzyme-like activities of gold nanoparticles.Beyond that,more applications based on the superior advantages of AuNPs are expected to be establishedSpherical AuNPs of 5-60 nm with satisfactory monodispersity were synthesized.The activating ability of AuNPs to H2O2 and O2 oxidation was enhanced through the regulation of size,structure and and elemental composition.The enhanced catalytic activities were put into applicationOn the basis of the research on the peroxidase-like activity,AuNPs were coupled with Rituximab antibodies to label specifically malignant lymphoma cells of Raji with CD20 overexpressed on the surface.As AuNPs could scatter strongly in dark-field,as well as catalyze the oxidation of 3,3'-diaminobenzidin(DAB)to stain the cells,they were used as contrast agents for cell microimaging in dark and bright field simultaneously.Besides that,DAB deposition was found to exhibit even better scattering property than AuNPs in dark-field.Based on this discovery,a novel dark-field micro-imaging method of detecting malignant lymphoma sections processed by conventional immunohistochemical DAB staining was establishedMost research of mimic enzyme are focused on the improvement in catalytic activity,the catalytic mechanism,and the application in biomedicine,environmental protection and other aspects.In spite of the competitive advantages,lacking substrate-selectivity is still a significant deficiency for mental mimic enzymes,and there also remains a broad improvable space in catalytic activity.The progress of AuNPs catalyzed Glu oxidation was identified to be similar with nature glucose oxidase(GOD)catalyzed reaction that consumed oxygen and produced hydrogen peroxide and gluconic acid.A novel AuNPs-based GOD mimic with enhanced catalytic activity and substrate-selectivity was constructed based on aminophenylboronic acid(APBA)and molecular imprinting technology.On one side,AuNPs were carried by polystyrene microspheres and modified with APBA as recognition molecules to bind to the adjacent hydroxyls of Glu.On the other side,APBA could be initiated to polymerize and form molecularly imprinted polymer shells with specific binding sites for the template molecules of Glu.This AuNPs-based GOD mimic(MIP)not only realized substrate-selectivity,but also improved the catalytic efficiency by about 127 times by increasing the affinity to Glu.Beyond that,heptadecafluoro-n-octyl bromide nanoemulsions with a function of providing oxygen were introduced to build PFOB-MIP and gained an improvement in catalytic efficiency by about 270 times.The catalytic number of a single GOD molecule of 5000 U/mg was 1.25×10-4 s-1 while a single MIP and PFOB-MIP could reach up to 5.87×105 s-1 and 8.14×105 s-1,respectively.This molecular imprinting based GOD mimic was employed to detect the Glu in drinks and obtained similar results with GOD.Taking advantage of the molecular imprinting based GOD mimic,a good linear results were gained in the detection of blood Glu of 1-50 mM through both coloration and electrochemical paper-based chipsTo achieve a further improvement in the catalytic activity,AuNPs were composited with other precious mental elements.Composite nanomaterials of gold,silver and platinum with different compositing ratios and structures were prepared,and gold-platinum alloy nanoparticles(AuPtNPs)with the highest catalytic activity was screened out.AuPtNPs with a diameter around 10 nm of different Au-Pt ratio was prepared to explore the effect of compositing ratio to catalytic activity.Au-Pt alloy nanoparticles with a Au-Pt molar ratio of 1:1 were found to have the highest GOD-like activity due to the combined effects of size and elementary composition.Besides of that,AuPtNPs with more Au tend to exhibited catalase-like activity while AuPtNPs with more Pt tend to exhibited peroxidase-like activity under same pH.On this basis,AuPtNPs with enhanced GOD-like activity were adsorbed to the surface of magnetic microspheres to construct molecular imprinting based GOD mimics(AuPt-MMIP).The catalytic number of a single AuPt-MIP could reach up to 1.42x 106 s-1,and AuPt-MMIP was also easier to magnetic separated.The recovery ratio and the reusability was 95.55%and 93.31%after 3 times of reuse,respectively.In conclusion,high-performance AuNPs-based mimics were obtained through size controlling,molecular imprinting as well as elemental compositing,and applied into in vitro detection of malignant lymphoma and Glu.The relationships between regulation methods and the catalytic properties of AuNPs-based mimics were explored and elucidated.Three important conclusions could be drawn from the research.The peroxidase,GOD and catalase-like activities of gold-based nanoparticles exhibited obvious uptrend with the decrease of size.The construction of molecularly imprinted polymer shells led to an improvement in substrate-selectivity as well as catalytic efficiency.Besides that,controllable Ag and Pt composition contributed to increased catalytic activities.