DNA Sensitivity Detection Based On Thin Film Nanopore

Due to the advantages of low cost,short time and high efficiency,single molecule detection technology based on nanopore has gradually become the most promising detection technology in the third generation of gene sequencing technology.Thin film nanopore,as a thin solid-state nanopore,has unique advantages in the field of DNA detection.To explore the detection of DNA molecular sensitivity in thin film nanopore,the transport of ions and DNA molecules in graphene nanopore was studied by molecular dynamics simulation and experiment,and the probe method to improve the detection of DNA sensitivity was explored.Specific work and results are obtained as follows:1)Molecular dynamics simulation was used to study the effects of applied voltage,solution concentration,diameter of graphene nanopore,number of graphene lamellae and wall charge of graphene nanopore on the transport characteristics of ions and DNA molecules in graphene nanopore.It was found that the ion current through the nanopore increases linearly with the increase of nanopore size,applied voltage and solution concentration,but decreases with the increase of graphene film layers;When the wall of the nanopore is charged,the ions which are opposite to the wall charged are easier to pass through the nanopore,and their contribution to the ion current is larger.the time of DNA passing through the nanopore decreases with the increase of applied voltage and nanopore size,but has no obvious correlation with solution concentration,but increases with the increase of graphene film layers;The current amplitude of the blocking ion increases linearly with the increase of applied voltage and solution concentration,but decreases with the increase of nanopore size and the number of graphene film layers;The shift time of DNA passing through positive holes on the wall is less than that of negative holes,which proves that the speed of DNA passing through holes can be slowed down by adjusting the wall charge of nanopore.2)Graphene samples were obtained by mechanical peeling method and transferred to silicon nitride substrates.Graphene nanopore was obtained by focused ion beam etching.The ion and DNA molecular detection experiments in graphene nanopore were carried out.It was found that the conductivity of nanopore is linear with the pore size,but has complexrelationship with the solution concentration;It is feasible to use graphene nanopore to detect DNA molecule.3)The comparative experiment of graphene nanopore and silicon nitride nanopore on DNA detection was studied,and it was found that the blocking ion current amplitude and the time of passing through the pore are obviously higher than those under silicon nitride nanopore.It proves that graphene nanopore has higher sensitivity in DNA detection and can achieve higher detection precision.4)The probe method to improve the sensitivity of DNA detection was preliminarily explored by using MATLAB simulation and experimental methods.It was found that probes with more bases can achieve high coverage rate and read the base information of DNA well;DNA bound to probes can produce larger blocking ion current value when passing through nanopore,which is different from the current signal of individual DNA.It shows that probes are feasible to detect DNA molecules.