Preparation And Sensing Application Of Metal-based Nanoenzymes

Nanozyme,a new type of artificial mimetic enzyme,has been widely used in many fields such as biosensing,environmental detection,food safety,medical diagnosis,and other fields due to their unique properties such as excellent stability,high catalytic activity,simple preparation,and low cost.In recent years,colorimetric sensing methods based on different nanozymes have been extensively applied in point-of-care testing(POCT)fields.However,the practical application of such nanozymes-based POCT methods still requires to be strengthened by continuously optimizing the design of new nanozymes and simple sensing signal readout.Based on this,we synthesized some new metal-based nanozymes with good oxidase-like activity and peroxidase-like activity,and successfully applied them into the construction of colorimetric and photothermometric sensing systems as the new POCT strategies for the analysis of some important life-related small molecules.This thesis is divided into four chapters as follows:Chapter 1:The development,classification,regulation mechanism of nanozymes were summarized,and the application of metal-based nanoenzymes in colorimetric and photothermometric sensing was also discussed.Chapter 2:Cobalt hydroxide nanoflakes(CoOOHNFs)were synthesized by using redox method and its oxidase-like properties were investigated carefully.CoOOHNFs could directly catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine(TMB)to generate its blue oxidation product(TMBox).Acid phosphatase(ACP)can hydrolyze ascorbyl phosphate(AAP)to produce ascorbic acid(AA),and the in situ AA can further reduce Co³⁺into Co²⁺.Which in turn leads to the decomposition of CoOOHNFs,resulting in the significant inhibition of CoOOHNFs nanozyme activity.Taking the advantage of the good photothermal response of TMBox under 808 nm laser irradiation,the color signal readout in this reaction system was successfully converted into a temperature signal,finally enabling a simple readout conversion of the proposed sensing system.Based on this,we successfully constructed a new simple and portable colorimetric and photothermometric sensing method for the detection of ACP with the limit of detection(LOD)of 0.0198 m U/m L and 0.0373 m U/m L,respectively.Chapter 3:We synthesized gold-copper nanoparticles(AuCuNPs)nanoparticles by the using"one-pot method"at room temperature for the first time,and investigated its oxidase-like activity characteristics.Under physiological p H conditions,AuCuNPs could oxidize the colorless TMB to its blue oxidation product(TMBox)in the presence of H₂O₂.Taking the benefit of the good photothermal effect of TMBox,we successfully established a new colorimetric and photothermometric sensing method for the detection of H₂O₂ with a LOD of 75.63?M and 108.9?M,respectively.This developed method not only breaks the limitation of low catalytic activity of conventional nanozymes under physiological p H conditions,but also extends the application of metal-based nanozymes for POCT analysis in biological and medicial analysis.Chapter 4:The progress and application of the colorimetric and photothermometric sensing methods based on metal-based nanozymes were summarized.The development direction of such nanozymes-based colorimetric and photothermometric POCT methods were also discussed and prospected.