Construction And Performance Study Of Cholesterol Electrochemical Biosensor

Cholesterol is essential in the human body which is directly involved in the formation of cell membranes and is also a raw material for the synthesis of vitamin D,bile acids and steroid hormones.Approximately 75%of human cholesterol is synthesized by itself and 25%is taken from food.The level of cholesterol should be maintained at a normal concentration range both in foods and serum,and it is of great significance of the content determination for clinical disease diagnosis and prevention.In this thesis,the cholesterol electrochemical enzyme biosensors were constructed based on graphene and mediator materials in order to apply into the analysis or dectection of the practical samples.The synthesis of doped graphene material,its use for enzyme immobilization and enzyme immobilization methods,diffusion-typed electron mediator for homogeneous catalyst system were taken into main research,it was divided into the following sections:A graphene-doped material was synthesized with pyrrole as a nitrogen source,and graphite oxide was reduced by a hydrothermal method,followed by freeze-drying,and finally under high temperature calcination.And the cholesterol enzyme modified electrode was constructed for the detection with doped graphene as the carrier,ChOx as the catalyst,Nafion as the binder,and cyclic voltammetry was used into research,the response to cholesterol was 0.02⁵.46mmol/L,the sensitivity was higher in the low concentration range of 0.02⁰.49 mmol/L whereas there was a good linear relationship in the high concentration range of 0.49⁵.46mmol/L,the linear equation was I??A?=-9.184+0.539C?mmol/L?with R²=0.992 and a sensitivity of 7.7 mA·mol^-1·cm^-2.The system was with a strong anti-interference ability as well as good reproducibility and stability as a means of cholesterol detection.Cholesterol enzymatic biosensor using ChOx was constructed on the basis of TEMPO electrocatalytic oxidation on H₂O₂.The catalytic effect of TEMPO on H₂O₂ was confirmed,the catalytic range was 0¹66.7 mmol/L,the linear relationship was 0⁴.97 mmol/L with equation I??A?=38.831+21.397C?mmol/L?,R²=0.998 and a sensitivity of 305.67 mA·mol^-1·cm^-2.TEMPO was used as the catalyst for H₂O₂ and the conductive mediator between the electrode and the electrode with ChOx as a catalyst,then a homogeneous enzyme system biosensor was constructed for the detection of cholesterol,the response to cholesterol was 0.01².61 mol/L with the linear equation I??A?=42.016+3.659C?mmol/L?and R²=0.990.The detection limit was 1.64×10^-5 mol/L?S/N=3?with a sensitivity of 52.27 mA·mol^-1·cm^-2.The biosensor was with good performance in terms of anti-interference,reproducibility,stability and reproducibility.And the catalytic performance of cholesterol applications of TEMPO,TEMPO-OH and TEMPO-NH₂ catalysts were compared,the maximum response concentration of TEMPO-NH₂ to cholesterol was 2.2 mmol/L whereas the maximum response to cholesterol of TEMPO and TEMPO-OH was 2.6 mmol/L.Cholesterol enzymatic biosensor using ChOx was constructed on the basis of ABTS electrocatalytic oxidation on H₂O₂.The electrochemical catalytic effect of ABTS on H₂O₂ was confirmed,the catalytic range was 0²0 mmo L/L with the equation I??A?=33.654+26.505C?mmol/L?and R²=0.991,the detection limit was 8.19×10^-5 mol/L?S/N=3?with a sensitivity of378.64 mA·mol^-1·cm^-2.The detection of cholesterol homogeneous system enzyme biosensor was constructed with ABTS as a catalyst for H₂O₂ and the conduction between the electron and the electrode mediator,ChOx as a catalyst.The interaction between ABTS,cholesterol and ChOx was verified.And the response to cholesterol was 0.005².50 mmol/L,the linear equation was I??A?=18.330+10.410C?mmol/L?with R²=0.998,the detection limit was2.84×10^-5 mol/L with a sensitivity of 148.71 mA·mol^-1·cm^-2,showing good anti-interference,reproducibility,stability and reproducibility.The cholesterol enzyme biosensor constructed in this study is expected to be used for the analysis and detection of total or free cholesterol in food and serum samples such as meat,eggs,margarine and fish oil,and provides the control and good application prospects for the detection of cholesterol in serum and food.It is of great impact and significance of the study of cholesterol sensors.