Fluorescent And Photothermal Sensing Based On The Peroxidase Mimics Activity Of The BSA@Au Nanoclusters

Nanoenzymes are a class of nanomaterials that possess the catalytic activity like natural enzymes.They are a new type of artificial enzyme mimics.Different from natural enzymes and other biocatalysts,the catalytic activity of nanoenzymes mainly derived from their special nanostructures,which can improve their stability,catalytic activity and processability,making up for the shortcomings of natural enzymes to a certain extent,and therefore nanoenzymes have a wide range of applications in the fields of biomedicine,environmental protection and energy technology.As an interdisciplinary field between nanotechnology and biology,nanoenzymes combine the advantages of both nanomaterials and enzymes.On the one hand it has an enzyme-like catalytic activity,while on the other hand it retains the unique physicochemical properties of the nanomaterial.Peroxidase-like enzymes account for more than half of these nanoenzymes.However,most of the current studies on peroxidase-like activity mainly focus on catalytic color development reactions,failing to take full advantage of the unique properties of nanomaterials themselves,which are relatively single in terms of the principles of method construction and lack further extended applications.Therefore,the development of new sensing methods using the peroxidase-like activity of nanoenzymes and the physicochemical properties of nanomaterials,is of great importance for the development of nanoenzymes in analytical sensing.Gold nanoclusters are a class of multifunctional nanoenzymes that combine enzyme-like activity and luminescent properties,which are widely used in analytical sensing.In this thesis,gold nanoclusters protected by bovine serum albumin（BSA@Au NCs）were synthesised by using a chemical reduction method.Based on the dual properties of BSA@Au NCs,which have excellent peroxidase-like activity and fluorescent properties,a fluorescent sensor for monitoring human uric acid levels and a photothermal sensing platform for monitoring heavy metal ion contamination in the environment have been constructed.Details of the work contents and results are as follows:（1）Based on the peroxidase-like activity and fluorescence properties of BSA@Au NCs,this work constructd a fluorescent sensing method for the detection of hydrogen peroxide and uric acid using a dual inner filter effect.The peroxidase-like activity of BSA@Au NCs can cause the oxidation of 3,3’,5,5’-tetramethylbenzidine（TMB）to produce a blue product（ox TMB）.This work found that the two absorption peaks of ox TMB overlapped with the excitation and emission peaks of BSA@Au NCs,respectively,causing efficient quenching on the fluorescence of BSA@Au NCs.Experimental and computational results suggested that this quenching mechanism can be attributed to the dual inner filter effect（IFE）.A facile fluorescence sensing method for the detection of hydrogen peroxide（H₂O₂）and uric acid（UA）was developed based on dual IFE,using the dual nature of BSA@Au NCs as peroxidase mimics enzymes and fluorescent reporters.Under the optimal detection conditions,the detection range of H₂O₂was 0.50-50μmol/L with a detection limit of 0.44μmol/L,and the detection range of UA was 0.50-50μmol/L with a detection limit of 0.39μmol/L.The method developed has been successfully applied to the determination of UA in human urine and has potential for application in biomedicine.（2）Based on the peroxidase-like activity of BSA@Au NCs and the photothermal effect of ox TMB,this work constructd a photothermal sensing method for the quantitative detection of Hg²⁺using a thermometer.By studying the peroxidase-like activity of BSA@Au NCs,it was found that the strength of the activity was related to the amount of Au⁺contained on the surface.Using the efficient and specific binding between Hg²⁺and Au⁺,the peroxidase-like activity of BSA@Au NCs can be inhibited,thus hindering the production of ox TMB.The amount of Hg²⁺and ox TMB were inversely proportional.Due to the photothermal conversion properties of ox TMB under near infrared laser irradiation,simple,low cost and convenient quantitative detection of Hg²⁺in the environment can be achieved by temperature signal readout with a detection range of 0.5-15μmol/L and a detection limit of 0.17μmol/L.The method evaluates the Hg²⁺adsorption performance of the adsorbents chitosan and activated carbon to screen for highly efficient Hg²⁺adsorbents.The method took advantage of the instantaneous readings of portable thermometers,realizing quantitative detection of Hg²⁺under resource-limited conditions,and also provided a new strategy for the instrument-free detection of Hg²⁺in a variety of complex scenarios.