▎ 摘　　要

NOVELTY - Preparation of electrochemical sensor involves polishing (i) a glassy carbon electrode into a mirror surface with alumina polishing powder, and cleaning with ultrapure water, dripping (ii) the electrode surface into gold-silver/reduced graphene oxide-polydopamine dispersion, drying, rinsing and drying, continuously dripping (iii) the electrode into apolipoprotein E4 capture antibody, rinsing and drying in a refrigerator at 4 degrees C, continuously dripping (iv) the electrode into bovine serum albumin solution to seal non-specific active sites on electrode surface, rinsing to remove unbound bovine serum albumin and drying, continuously adding (v) apolipoprotein E4 detection antibody solution at different concentrations, rinsing with ultrapure water, and drying in a refrigerator at 4 degrees C, and continuously dripping (vi) the electrode into detection antibody gold nanoparticle-reduced graphene oxide-polystyrene nanosheet-antibody solution, heat-preserving, rinsing with ultrapure water, and drying. USE - Preparation of electrochemical sensor based on gold nanoparticle-reduced graphene oxide-polystyrene nanosheet used for detecting apolipoprotein E4 (claimed) in immune analysis and biosensing technology. ADVANTAGE - The method enables preparation of electrochemical sensor based on gold nanoparticle-reduced graphene oxide-polystyrene nanosheet having improved stability and catalytic performance. The electrochemical sensor enables quantitative detection of apolipoprotein E4 with high sensitivity, desired selectivity and low detection limit. In the preparation of electrochemical sensor, the gold-silver/reduced graphene oxide-polydopamine is used a base material, and the gold-silver/reduced graphene oxide-polydopamine has excellent conductivity, large specific surface area and high catalytic activity, and can effectively reduce background signal. DETAILED DESCRIPTION - Preparation of electrochemical sensor based on gold nanoparticle-reduced graphene oxide-polystyrene nanosheet involves polishing (i) a glassy carbon electrode having a diameter of 3-5 mm into a mirror surface with alumina polishing powder, and cleaning with ultrapure water, dripping (ii) the electrode surface into 6 mu l, 1-3 mg/ml gold-silver/reduced graphene oxide-polydopamine dispersion, drying at room temperature, rinsing the electrode surface with ultrapure water, and drying at room temperature, continuously dripping (iii) the electrode into 6 mu l, 8-12 mu g/mL apolipoprotein E4 capture antibody, rinsing with ultrapure water, and drying in a refrigerator at 4 degrees C, continuously dripping (iv) the electrode into 3 mu l, 0.5-1.5 mg/mL 1% bovine serum albumin solution to seal non-specific active sites on the electrode surface, rinsing the electrode surface with ultrapure water to remove unbound bovine serum albumin, and drying in a refrigerator at 4 degrees C, continuously adding (v) 6 mu l, 0.03-2000 ng/mL apolipoprotein E4 detection antibody solution at different concentrations, rinsing the electrode surface with ultrapure water, and drying in a refrigerator at 4 degrees C, and continuously dripping (vi) the electrode into 6 mu l, 1.5-3.5 mg/mL detection antibody gold nanoparticle-reduced graphene oxide-polystyrene nanosheet-antibody solution, heat-preserving in a refrigerator at 4 degrees C for 40 minutes, rinsing with ultrapure water, and drying. An INDEPENDENT CLAIM is included for use of the electrochemical sensor based on gold nanoparticle-reduced graphene oxide-polystyrene nanosheet for detecting apolipoprotein E4. The detection method involves using an electrochemical workstation including a three-electrode system comprising a saturated calomel electrode which is a reference electrode, a platinum wire electrode which is an auxiliary electrode and the electrochemical sensor which is a working electrode, using 10 ml, 10 mmol/L potassium ferricyanide solution for testing, and using chronoamperometry to detect apolipoprotein under the condition of a detection voltage of -0.4 V, an input voltage of -0.4 V, a sampling interval of 0.1 second and a running time of 300 seconds. When the background current is stabilized, 10 mu l, 5 mol/L hydrogen peroxide solution is injected into 10 ml, 50 mmol/L phosphate buffer solution with a pH of 7.38 every 50 seconds, and the current changes are recorded.