Research On New Methods Of Biosensing Based On Several Nanomaterials For Detection HBV DNA And Glucose

In the 21st century,science and technology have been developed rapidly.The diversity of detection and analysis method made us know more about ourselves and the environment.We paid more and more attention to the environment and ourselves.Many testing methods and analysis method in the past have been eliminated.With the development of science and technology,there have been many new type detection means,biosensor is one of the representative.Biosensor used the biological active substances as sensitive unit,it converted the response signal into a physical chemical signals to analyze the target and testing by a transducer.Because of good specificity and strong anti-jamming capability,it made biosensor can high sensitive detection of target objects under the eomplex environment.Biosensor could detect the target in a short time.The operation was very simple,didn,t need a professional operation.These also made biosensor as a useful tool for detection.Biosensor had a broader development because of the advent of nanomaterials.Nanomaterial had the very high specific surface area,it could absorb a variety of target molecules.Different nanomaterials had different nature.We used nanomaterials in order to design a series of different kinds of biosensors.In this thesis,we used the outstanding performance of nanomaterials to design our experiments,which was used for the sensitive detection of hepatitis B virus(HBV)DNA,H2O2 and glucose.The detailed content was described as follows:(1)A novel versatile fluorescence polarization(FP)platform based on the SiO2 NP-DNA/Ag NC sandwich structure as a signal enhancer for optical detection of HBV DNA in biological media was developed.We designed two DNA probes:one was the Ag-DNA probe,the other was the En-DNA probe with guanine-rich DNA sequences was tagged at the 5'-terminus with a biotin molecule,which was utilized to link the En-DNA probe to SiO2 NPs through the noncovalent biological interaction of streptavidin at the surface.In the absence of target HBV DNA,a relatively small FP value could be found.What was interesting was that in the presence of target HBV DNA,the sandwich structure would be formed at the surface of SiO2 NPs resulting in a substantial increase of the FP value due to the enlargement of the molecular volume of the formed SiO2 NP-functionalized DNA/Ag NC sandwich structure with slow rotation.Therefore,the detection of target HBV DNA could be easily realized by monitoring the increased FP values in the presented method.The relative FP value AFP(AFP=FPT-FP0,where FP0 and FPT are the FP values before and after addition of target HBV DNA,respectively)was linearly related to HBV DNA within the concentration range of 1-800 nM.The limit of detection of this method was estimated to be 0.65 nM,which is three times the standard deviation corresponding to the blank sample detection and is at least one order of magnitude lower than those of the previously reported dyelabeled DNA/QD homogeneous biosensor system in FRET mode.Moreover,the proposed FP biosensors also exhibited a wider dynamic range than other methods.We believe that the new proposed biosensor may hold great promise as a versatile tool for nucleic acid analysis in bioanalytical and clinical diagnostic applications.(2)In this paper,hemin-functionahzed WS2 nanosheets(hemin/WS2-NSs)were synthesized by a simple wet-chemical strategy and it was used for the detection of H2O2 and glucose.To assess the peroxidase-like activity of the hemin/WS2-NSs,TMB-H2O2 reaction was used as a model reaction system.Hemin/WS2-NSs could effectively catalyze the reaction of peroxidase substrate 3,3,5,5,-tetramethylbenzidine(TMB)in the presence of H2O2 to produce the blue color reaction.we provide the first report that Hemin/WS2-NSs exhibit intrinsic peroxidase-like activity,which follows the typical Michaelis-Menten kinetics and ping-pong mechanism.Hemin/WS2-NSs have higher catalytic activity than HRP and better stability.We use hemin/WS2-NSs as a colorimetric biosensor for the detection of glucose with a linear range of 0.5×10-5-2.×10-4 M with a detection limit of 1.5×10-6 M.The present label-free colorimetric assay could be used to quantify glucose in human serum samples.(3)The g-C3N4-Fe3O4 nanocomposites were synthesized through a simple method and this new composite possesses excellent peroxidase-like activity,could effectively catalyze the reaction of peroxidase substrate TMB in the presence of H2O2 to produce the blue color reaction with a maximum absorbance at 369 nm and 652 nm.The catalytic activity of g-C3N4-Fe3O4 nanocomposites was dependent on temperature,pH,and time.Under our Experimental optimum assay conditions,we evaluated the sensitivity of the proposed label-free colorimetric method for the detection of H2O2 and glucose with a limit of detection of 0.3 ?mol L-1,0.25?mol L-1.We evaluated the applicability of the proposed method based on the g-C3N4-Fe3O4 for the determination of H2O2 glucose in complex samples,the results demonstrated that the sensing system has a high selectivity for H2O2 and glucose detection.These results indicated the validity of the proposed label-free colorimetric method for the determination of glucose in real biological samples.In conclusion,we used the outstanding performance of nanomaterials to design our experiments,which was used for the sensitive detection of hepatitis B virus(HBV)DNA and glucose.This work provides nanomaterials with a wider range of purposes and a more broad thinking to design new sensors.