Single Glass Conical Nano-bionic Channel Based On Photo-sensitive Polymer Modification

Ion channels embedded in biological membranes not only play a vital role in various physiological processes such as substance conversion and nerve conduction by regulating the selective transmembrane transport of molecules and ions but also widely applicated in vitro research as a versatile natural material.However,these ion channel proteins are not stable,not adjustable in size,and too sensitive to the external environment,which limits their practical application in vitro to a certain extent.Therefore,researchers have prepared a variety of solid-state bionic nanochannels.These bionic nanochannels can be functionally modified to simulate the material transmission and signal transduction functions of biological ion channels.They are widely used in biosensing,molecular ion detection,nanofluidic devices,etc.The dissertation is dedicated to studying the ion transport process of nanopores functionalized with spiropyran polymers to simulate the function of biological ion channels.The dissertation consists of four chapters:In the first chapter,the research progress of bionic solid-state nanopores and the classification of them based on different materials were firstly expounded.Then the three ion transport characteristics of nanopores were introduced.Apart from this,the application of solid-state nanopores in smart bionics,nano-sensor,and other aspects was summarized.Finally,the propositions for the thesis were put forward.In the second chapter,the process of prepar ing a single glass tapered nanochannel was first introduced briefly.Then the method and procedure of measuring the conical tip radius of the nanochannel was described.Finally,the results of using scanning electron microscope(SEM)and Nikon inverted fluorescence microscope to characterize the morphology of single glass conical nanochannel are described.In the third chapter,photo-sensitive molecule spiropyran-linked methacrylate(SPMA)was grafted into the inner wall of the glass conical nanochannel to form a layer of photosensitive homopolymer film by surface-induced atom transfer radical polymerization(SI-ATRP)reaction.Based on this functionalized nanopore,a lightcontrolled biomimetic switch with pH-dependent rectification characteristics was constructed.The experimental results showed that the surface of the inner wall of the nanochannels functionalized with poly-spiropyran-linked methacrylate(P-SPMA)is rich in the large number of spiropyran(SP)groups.The SP groups can undergo a configuration change under ultraviolet light radiation,from a hydrophobic SP structure ring to a hydrophilic merocyanine(MC)configuration,which can be converted into a hydrophobic structure under visible light irradiation.Based on this,the biomimetic switch can be reversibly opened and closed under alternating radiation of ultraviolet light and visible light.Moreover,repeatability performance is excellent.At the same time,the ring-opening MC structure is amphoteric,which has an acid-base balance in the electrolyte solution.By adjusting the pH of the solution,MC can be positively charged,negatively charged,or even uncharged.So that,different pH-dependent rectification mechanisms for the biomimetic nanochannel were implemented,namely positive rectification(anion-selective),negative rectification(cation-selective),and no rectification(non-selectivity).This pH-dependent rectifying reversible light-controlled biomimetic nanochannel provides a feasible idea for selective light-controlled drug release in different human environments.In the fourth chapter,the photo-sensitive molecule SPMA and the temperaturesensitive molecule methacrylic acid-N,N dimethyl-aminoethyl(DMAEMA)were copolymerized to the inner surface of the nanopore by SI-ATRP reaction.Therefore,a biomimetic device that responds to external stimuli was proposed.The alternating radiation of ultraviolet and visible light can make the biomimetic device act as a gate reversible opening and closing.Meanwhile,adjusting different environmental temperatures,the intermolecular hydrogen bond formed between the PDMAEMA part of the copolymer and the water molecule will be affected by the temperature.As a result,the morphology of the surface polymer will change and the surface properties of the nanopore will also change to regulate the ion current in the nanochannel.Besides,openloop MC is an amphoteric substance,which can be protonated and deprotonated over a wide pH range.Based on it,the nanochannel achieved a rectification inversion.This multi-response biomimetic nanochannel has important research significance for creating a more intelligent bionic system.