Small Molecule Biomarker Sensors Based On Nanocatalytic Materials

The levels of small molecular biomarkers in the human body often indicate the presence of diseases and play an important role in clinical diagnosis and human health monitoring.Traditional methods for detecting small molecule biomarkers mainly include chromatography,fluorescence,enzyme-linked immunosorbent assay,etc.These methods have high sensitivity and selectivity,but the operation is complicated,and the detection time-consuming.In addition,these methods need expensive instruments and professional operators,which limit their application in point-of-care tests.Alternatively,electrochemical biosensors have been widely used in clinical diagnosis,environmental monitoring,food safety,and scientific research due to their ease to use,low cost,rapid response,high sensitivity,and portability.In recent years,the combination of nanomaterials and electrochemical sensors has further improved the sensor performance.In this thesis,two nano-catalytic materials were designed and synthesized to modify the electrochemical biosensor for the detection of neurotransmitter 5-hydroxytryptamine(5-HT)and insulin,respectively.1.Senary high-entropy alloy nanoparticles were synthesized by the thermal reduction method and loaded on the graphene nanofibers(GNF)as a catalyst for the electrochemical detection of 5-HT.Both cyclic voltammetry and amperometric method were used to characterize the modified electrode.The electrode shows good catalytic activity for the electro-oxidation serotonin,and the response current shows a good linear relationship with the concentration of serotonin in the range of 0.01?50.0 ?M,and the limit of detection(LOD)is 10 n M.At the same time,the electrochemical biosensor also shows high selectivity,which can distinguish serotonin from interfering substances.The sensor was used to detect serotonin in real human serum samples,showing potential in clinical diagnostics and neuroscience research.2.Graphene-like nickel hydroxide nanosheets were synthesized by the microwave method for electrochemical oxidation of insulin,and carbon black was mixed to enhance the conductivity.The catalyst weight ratio and the p H values of the background solution were optimized.As a result,the optimal weight ratio and p H value were 1:1and 13,respectively.In optimal conditions,the electrochemical detection of insulin showed high sensitivity,the response current shows a good linear relationship in the range of 0.01-100 ?M,and the LOD is 2.6 n M.Furthermore,the electrochemical biosensors based on nickel hydroxide nanosheets have good selectivity and reproducibility.This sensor can be used to measure the insulin concentration in the supernatant of ? cells(INS-1E)solution,which is expected to be used in the screening and evaluation of diabetes drugs.In this dissertation,the disposable screen-printed electrode was combined with modified nano-catalytic materials,and electrochemical characterization was carried out by an electrochemical workstation.Sample pollution was avoided,and the test response is fast.Test samples or real samples needed are only 5 ? 10 ?L.The two sensors have great potential in clinical detection and drug evaluation.