Biomimetic Applications Of Glass Conical Nanochannel

In living systems,there are a variety of biological nanochannels in cell membrane,endoplasmic reticulum membrane and nuclear envelope,which offer response to external environment stimuli and play key roles in signaling,mass transfer,transportation and nerve conduction.Inspired by these asymmetric structures and responsive ion transport of biological ion channels,synthetic nanochannels are being utilized and countless materials have been developed rapidly to stimulate the functions of their biological counterparts.Compared with the biological ion channels,artificial nanochannels possess the advantages of controllable geometry and size,excellent mechanical robustness,and functionalizational convenience.The nanodevices constructed by functional modification of artificial nanopores have been widely used in chemistry,biomedicine,material sciences,molecular biology and other fields.In this dissertation,the ion transport properties of the functionally modified glass conical nanochannels have been observed under various kinds of stimuli.The dissertation consists of six chapters.In the first chapter,the origin of artificial nanopores and complicated preparation technologies,the principle and influence factors of ion rectifier phenomenon and the applications of artificial nanopores in the biomimetic ion channels have been extensively reviewed.Finally,the plans for the dissertation have been put forward.The second chapter comprises of the detailed descriptions of fabrication process for single glass conical nanopores,the measurement method for the radius of the nanopores and the characterization of the morphology of nanochannelsThe third chapter includes the details regarding the combination of two glass conical nanochannels with silicone tube,and the detection of ionic current in KCl electrolyte solution via linear sweep voltammetry(LSV).The experimental results presented in this chapter,exhibit a very comprehensive idea that when the nanochannels are arranged in a series mode,the I-V curve appears as S shaped,if the directions of the diode rectifier nanochannels are same.However,In case of parallel arrangement,the ionic current is nearly equal to the sum of the current of two glass conical nanochannels applied with the same voltage and the diode rectifier curve turns out to be the same as obtained in series mode.This combination of nanochannels can be split into different functional modifications,and can be employed to build a logic switch.In the fourth chapter,a copolymer Poly[2-(dimethylamino)ethyl methacrylate]-co-[4-vinyl phenylboronic acid](P(DMAEMA-co-VPBA)),having undergone pH-,temperature-,and sugar-induced conformational transitions,was integrated into a single glass conical nanochannel to realize tri-stimuli based ion transport.The copolymer P(DMAEMA-co-VPBA)was introduced into the surface of the single glass conical nanopore channel via atom transfer radical polymerization(ATRP).In acid solution system,the tertiary amino groups of PDMAEMA backbone are protonated,in order to render the interior surface of the nanochannel as positive.Meanwhile,the phenylboronic acid groups of PVBA backbone are ionized under basic medium,causing the nanochannel to have a negative charge.The PDMAEMA backbone and PVBA backbone modified on the surface of nanochannel make up with each other in such a way that the nanodevice rectifies ion current in a broad range of pH.Moreover,the P(DMAEMA-co-VPBA)-modified nanochannel is capable of switching the conductivity between "low" and "high" ionic current states by tuning the temperature for the change of effective cross section owing to the conformational change of the copolymer brushes with temperature.The ionic current of P(DMAEMA-co-VPBA)modified nanochannel increases significantly when the temperature goes beyond the lower critical solution temperature(LCST).Furthermore,the P(DMAEMA-co-VPBA)modified nanochannel portrays commendable sugar responsive capacity,which can reversibly switch between the non-rectifying and rectifying states.In the fifth chapter,the details are enlisted about Poly-spironaphthoxazine polymers(P-SPMA),capable of offering response to light stimulus,its successful modification onto the surface of glass conical nanochannels via atom transfer radical polymerization(ATRP).The experimental results obtained,indicate the breaking of C-O bonds between the polymer brushes,resulting into the generation of phenolic hydroxyl functionalities on the channel surface upon UV-365 nm irradiation.This part of dissertation further elaborates the idea that under basic symmetric electrolyte conditions,the exposed phenolic hydroxyl groups were underwent ionization,exhibiting the cation-selective behaviour of the channel.The final part of the chapter includes the conclusion of the detailed and comprehensive experimental study carried out in the quest of completion for this dissertation and it sums up the whole story with the point that the present study will benefit the design of nanofludic devices for nanoscale chemical delivery and intracellular drug delivery.The final chapter includes the summarization of the key innovations in the research work and the possible future prospects of the mentioned work.