Research On The Rectification Characteristics Of Asymmetric Nanochannels And Its Application In DNA Detection

The technology of single-molecule detection on nanochannels has the advantages of simple method,no need for labels,and real-time monitoring.It has attracted wide attention in the fields of biology and chemistry.Compared with biological nanochannels,solid-state nanochannels have not only adjustable pore size and shape,but also excellent thermal and chemical stability under various conditions(p H,temperature,concentration,etc.).Therefore,they are widely used in the detection of nucleic acid,proteins and single cells.However,before applying solid-state nanochannels to the technology of single-molecule,the ion current rectification(ICR)of the channel cannot be ignored.ICR mainly studies the ion transport inside the channel.by changing the external stimulus,we can achieve the selective transport of ions in nanochannels based on gating mechanism..The ICR of solid-state nanochannels can better help us understand the translocation process of single-molecule substances inside nanochannels.Based on this,we take advantage of the conductivity,oxidation-reduction characteristics and good reversibility of polyaniline(PANI),and combine it with solid-state nanochannels to prepare positively charged PANI nanochannels.By imposing external stimuli,we change the Surface charge inside the channel and study the mechanism of ion transport.Finally,the prepared asymmetric PANI nanochannel was used to study DNA translocation in a crowded environment in vitro.The specific research is as follows:Firstly,we prepare inconsistent concentrations of aniline monomer and oxidant solutions.based on the template method,we make aniline polymerize along the inside of the nanochannel.Finally we successfully synthesize an asymmetric PANI nanochannel.By changing external stimuli,such as salt concentration,salt gradient,anion species,p H,transmembrane voltage,grid voltage,etc.,we found that these factors will affect the surface charge state inside the PANI nanochannel,and then affect the rectification of ionic current.Especially when preparing nanochannel devices based on gate voltage,the charge of PANI can be changed directly and in real time by applying gate voltage,and the ion selectivity of the nanochannel can be controlled.This not only provides theoretical support for ion diodes,energy harvesting and ion filtration,but more importantly,it can also be used for single-molecule detection,and real-time regulation of molecular perforation behavior,which provides DNA sequencing,proteins and virus detection Endless possibilities.Secondly,the study of ion transport inside the PANI nanochannel can be better used for DNA detection.By using the prepared asymmetric PANI nanochannel,we add different concentrations of PEG8000 to the buffer solution to simulate the crowded environment in vitro.Then we study the DNA translocation process in the crowded environment.The addition of the crowding agent improves the detection sensitivity and resolution of the nanochannel,and a rare double-pulse signal and current surge signal are observed.It is speculated that this is related to the adsorption and desorption of DNA on the pore wall.This experiment provides a kinetic analysis for the study of DNA perforation behavior,and puts forward a feasible idea for DNA sequencing and the detection of other small-sized protein molecules.