Application And Research Of Biosensors Based On Metal Nanoclusters In Biomolecular Detection

Metal nanoclusters are composed of exact number of metal atoms and surface ligands,usually less than 3 nm in size,they are a kind of ultra-small fluorescent nanomaterials with unique properties,and have become a research hotspot in recent years.Metal nanoclusters have great application potential in the fields of biosensors,biomarkers and biological imaging due to their significant advantages of low toxicity and high biocompatibility to environment and biological tissues.In contrast to conventional fluorescent probes,as novel fluorescent sensing probes with high sensitivity and selectivity,metal nanoclusters have ultra-small size,excellent optical properties,unique physical and chemical properties,and some notable improvements have been made in the application research of molecular sensing,biomedical research and catalysis.Fluorometric and colorimetric detection methods have high sensitivity,fast response,simple operation,which can better meet the requirements of biological analysis and have attracted extensive attention by researchers.However,many detection methods realize the detection of samples through the change of single wavelength fluorescence signal or colorimetric signal,which are easily interfered by many factors such as probe concentration,light source and complex matrix of the samples.The dual-signal sensor based on ratiometric fluorometric and colorimetric response can compensate for these shortcomings and quickly,economically,and efficiently analyze unknown samples.In this paper,we have established a series of dual-signal biosensors based on metal nanoclusters for the detection of biomolecules.In the first chapter,we gave a brief overview of metal nanoclusters and systematically discussed and summarized the synthesis methods,fluorescence characteristics and applications of metal nanoclusters in biosensoring.Finally,the main research contents and significance of this paper were clarified.In the second chapter,we synthesized gold-platinum bimetallic nanoclusters（Au-Pt NCs）using guanosine monophosphate（GMP）as a capping agent,and constructed a novel ratiometric fluorometric and colorimetric dual-mode sensor based on Au-Pt NCs and o-phenylenediamine（OPD）in order to detect glucose sensitively.Au-Pt NCs possessed strong fluorescence and peroxidase-like mimetic activity.Under the oxidation of glucose oxidase（GOx）,glucose can be oxidized to generate hydrogen peroxide（H₂O₂）,Au-Pt NCs with peroxidase activity can oxidize colorless OPD to produce yellow2,3-diaminophenazine（DAP）,which showed obvious UV absorption peak at 420 nm.And the UV absorption peak of DAP overlapped with the fluorescence emission peak of Au-Pt NCs,therefore,the oxidation product DAP quenched the fluorescence of Au-Pt NCs based on inner filter effect（IFE）.Glucose can be quantitatively detected by ratiometric fluorometric and colorimetric method at the same time with linear ranges of 0.01-0.4 m M and 0.05-0.4 m M,respectively,and detection limits（LOD）of 7μM and 11μM,respectively.This dual-mode sensing method improved the accuracy of detection,had good selectivity,and it was profitable to detect glucose content in human serum,which provided a new idea for the development and application of glucose related sensors.In the third chapter,we established a novel dual-signal sensing system in order to determine the activity ofβ-galactosidase（β-Gal）based on a dual emission probe assembled from negatively charged gold-platinum bimetallic nanoclusters（Au-Pt NCs）and positively charged Rhodamine B（Rh B）.In the presence ofβ-Gal,4-nitrophenylβ-D-galactoside（PNPG）was hydrolyzed to produce p-nitrophenol（PNP）.The fluorescence quenching of Au-Pt NCs was induced by IFE between PNP and Au-Pt NCs.However,PNP had no effect on the fluorescence of Rhodamine B.In addition,PNP showed an obvious UV absorption peak at 400 nm.Therefore,we successfully constructed the ratiometric fluorometric and colorimetric dual-signal biosensor based on Au-Pt NCs and Rhodamine B for the sensitive detection ofβ-Gal.The linear detection ranges of ratiometric fluorometric and colorimetric method were 2.5-25 U/L and 15-55U/L,respectively.Besides,the LOD of Au-Pt NCs and Rhodamine B fluorescence probe forβ-Gal were 1.2 U/L and 5.2 U/L,respectively.The developed detection assay was utilized detect the activity ofβ-Gal in real samples with high reliability and good selectivity,which opened up a new way for the further application of Au-Pt NCs in chemical sensing and biological analysis.In the fourth chapter,we summarized the main research contents of this paper,and proposed the current challenges and future prospects of metal nanoclusters in the analysis.