▎ 摘　　要

NOVELTY - Preparation of modified electrochemical DNA sensor includes mixing graphite powder and n-hexyl pyridinium hexafluorophosphate ionic liquid, grinding, putting into compact glass electrode tube, and inserting copper wire as conductor to obtain ionic liquid-modified carbon paste electrode (CILE); mixing chloroauric acid and sodium nitrate, performing potentiostatic deposition, washing, and vacuum-drying to obtain gold nanoparticles (AuNPs)/CILE; and dispersing with graphene oxide (GO), drying, performing constant potential reduction in phosphate buffer solution (PBS), washing, and drying. USE - Method for preparation of modified electrochemical DNA sensor (claimed) used for detecting Listeria monocytogenes gene sequence. DETAILED DESCRIPTION - Preparation of modified electrochemical DNA sensor comprises: (A) mixing graphite powder and n-hexyl pyridinium hexafluorophosphate ionic liquid at mass ratio of 2:1, grinding to obtain ionic liquid-modified carbon paste, putting into compact glass electrode tube, inserting copper wire as conductor, and reacting to obtain ionic liquid-modified carbon paste electrode (CILE); (B) mixing chloroauric acid and sodium nitrate to obtain electrolytic solution, depositing gold particles into surface of CILE through potentiostatic deposition using CILE as working electrode, platinum sheet as auxiliary electrode, saturated calomel electrode as reference electrode, washing with distilled water, and vacuum-drying to obtain gold nanoparticles (AuNPs)/CILE; (C) dispersing with graphene oxide (GO), naturally drying to obtain modified electrode GO/AuNPs/CILE, subjecting to constant potential reduction using phosphate buffer solution (PBS), thoroughly washing with double distilled water, and drying under nitrogen atmosphere to obtain partially reduced graphene oxide (p-RGO)/AuNPs/CILE; (D) soaking p-RGO//AuNPs/CILE in ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide dissolved in PBS, activating carboxyl group on surface of modified electrode, drip coating surface with amino-containing modified probe single-stranded DNA (ssDNA) sequence buffer solution to carry out covalent bonding of amino-modified probe sequence and carboxyl group forming an amide bond and a stable fixed ssDNA probes, naturally drying, and washing twice with 0.5 wt.% sodium dodecyl sulfate (SDS) solution and thrice with distilled water respectively to remove non-adsorbed probe sequence and obtain fixed probe sequence electrode (ssDNA/p-RGO/AuNPs/CILE); (E) directly coating ssDNA/p-RGO/AuNPs/CILE surface with target sequence-containing PBS, hybridizing at room temperature, and washing with 0.5 wt.% SDS and with distilled water twice to remove unhybridized target sequence and obtain hybridized electrode dsDNA/p-RGO/AuNPs/CILE; and (F) soaking in methylene blue (MB) adsorption solution, taking out, washing with 0.5 wt.% SDS and with distilled water twice, and measuring MB electrochemical behavior in tris-hydrochloride buffer solution through differential pulse voltammetry, in 1 mmol/L potassium ferricyanide and 0.5 mol/L potassium chloride mixed solution through cyclic voltammetry at scan rate of 100 mV/s, and in 10 mmol/L ferricyanide/ferrocyanide ions and 0.1 mol/L potassium chloride mixed solution through electrochemical impedance spectroscopy at frequency of 104-0.1 Hz.