Electrochemical Analysis Of Non-redox Active Substances Based On Nanochannel Arrays

Many non-redox active species play key roles in various body functions.Electrochemical analysis methods have attracted more and more attention because of their advantages such as high spatial resolution,high temporal resolution,easy miniaturization and in situ real-time sensing.However,the electrochemical inactive ions are difficult to be detected directly based on their own Faraday signal,because their redox potential exceeds the potential window of water decomposition and the over-potential is too high to observe the response signal in the normal polarization window.In addition,in vivo environment is complex,containing many species with similar structure and great content difference,resulting in huge interference in vivo determination.Therefore,the development of effective electrochemical strategies for the in vivo analysis of non-redox active ions is of great significance for understanding and studying their ionic mechanism and their role in physiological or pathological diseases.According to extensive literature research and design,this paper aims to solve the critical scientific problems encountered in the in vivo electrochemical detection of non-redox active species,and are summarized as follows:(1)Functional mesoporous Carbon-Silica/AAO nanochannels with enhanced selectivity for K~+transport.K~+is an important electrochemical inactive ion in vivo,which is closely related to various physiological and pathological activities,such as nerve conduction,regulation of blood pressure and pH,and regulation of membrane potential in living cells.In this work,a highly selective functional asymmetric nanochannel electrochemical sensor was constructed,providing a new idea for the detection of other non-redox active species in vivo.At the beginning,a mesoporous carbon-silica film material(MCS)was designed and synthesized,and an asymmetric nanochannel(MCS/AAO)was constructed by combining MCS with anodic alumina porous array(AAO)with a pore size of about 40 nm.The negative charge property of MCS can filter cations,playing a selective role.On the other hand,MCS/AAO was functionalized by the acylation reaction of the carboxyl group on the surface of MCS with 4-aminobenzo-18-crown-6(Crown)molecule(Crown/MCS/AAO).The selective sensing of K~+was realized by the specific interaction between Crown molecule and K~+.The results demonstrated the functional nanochannel has high selectivity and high accuracy for the detection of K~+,with a good linear response to K~+in the content range of0.05 m M-1.00 m M.It has been successfully applied to the determination of K~+in serum of normal and hypertensive rats.The results indicated that compared with the normal rats,the concentration of K~+in the serum of hypertensive rats decreased by 41.1%,suggesting that K~+is an important factor in blood pressure regulation.(2)Artificial ion pump based on graphdiyne-functionalized nanochannel array for highly efficient transfer of acetylcholine across liquid/liquid interface.Acetylcholine(ACh)is an important non-redox active neurotransmitter in brain,which is closely related to neurodegenerative diseases such as Alzheimer’s disease.However,the amount of ACh in the brain is quite low,down to～nM,and lots of co-existing interferents,such as choline(Ch),which is very similar to its structure and2-3 magnitude higher than ACh.In order to solve the above scientific challenges,in this work,we put forward the strategy of artificial ion pump,built a liquid/liquid interface electrochemical detection platform based on graphdiyne-functionalized nanochannel array,and realized the trace detection of ACh in the brain.Firstly,graphdiyne was modified inside AAO to build a nano-limited environment(AAO/GDY).Then AAO/GDY was used to construct liquid/liquid interface electrochemical detection platform.On the other hand,a specific recognition ligand of ACh,calix[4]arene molecule(CX4-1),was synthesized as molecular facilitator to trigger the transfer of ACh cations across liquid/liquid interface(AAO/GDY/CX4-1).The negative charge property and porous structure of GDY can adsorb ACh.Combined with the specific interaction between CX4-1and ACh,GDY and CX4-1 synergistically accelerated the transport of ACh at the liquid/liquid interface and realized high sensitivity and high selectivity detection for ACh,with a good linear response to ACh in the concentration range of 0.2 nM-10 nM,and the detection limit was 0.078nM±0.013 nM.Finally,the liquid/liquid interface electrochemical detection platform was successfully applied to the online detection of ACh in the brain microdialysis of rats with memory impairment(MI)of different genders.The results indicated that the process of MI is closely related to gender.Compared with normal rats,the amount of ACh in the brain microdialysis of female rats decreased by 63.1%after 30 days of intraperitoneal injection of scopolamine(SCO),while that of male rats only decreased by 35.3%.The results showed that female rats were more likely to suffer from memory damage.