Research On The Construction Of Impedance Sensor And Its Chiral Recognition Of Amino Acid

Chirality is a common phenomenon in nature.Chiral molecules with different configurations may have different properties.As a common chiral compound most amino acids exist in the body in the L-configuration except glycine;whereas,D-type amino acids only exist in the cell wall of bacteria and some antibiotics,which may be harmful to the human.Besides,amino acids are not only the basic building blocks of proteins,but also essential biomarkers for a variety of metabolic diseases.Therefore,the recognition of chiral amino acids is of great significance in many fields such as chemistry,biology,pharmacy and agronomy.In the development of technologies for the identification and analysis of chiral amino acids,electrochemical methods have attracted widespread attention due to their outstanding advantages such as low cost,easy operation,high sensitivity,and real-time online detection.Traditional electrochemical methods for identifying chiral amino acids by peak current or potentiometry can still be used,but their detection limits are difficult to meet clinical needs.In addition,traditional voltammetry can recognizes chiral amino acids,which has a strong dependence on the electrochemical activity of the target substance.That is,it is difficult to achieve recognition of weak and non-electrochemically active amino acids.The innovation of my thesis lies in the use of the advantages of electrochemical methods to develop some novel impedance type electrochemical sensors with an electron transfer resistance as the output signal.This approach can solve problem about the sensitivity of traditional voltammetry,and discriminate amino acids in the clinical requirement.Also our proposed method can achieve electrochemical recognition of weakly and non-electrochemically active chiral amino acids.The main tasks are as follows:?1?The use of bovine serum albumin?BSA?with a special spatial structure such as expansion ratio,hydrophobic displacement,etc.,thus being a chiral selector,successfully constructed a BSA-based impedance electrochemical sensor.The label-free sensor shows good recognition performance of weakly electrochemically active amino acids:L-aspartic acid?L-Asp?in a concentration range of 5 nM to10000 nM without other substance as a marker,and the minimum detection limit is0.6 nM.At the same time,the sensor experiment can elute the target substance by constructing a non-imprinted impedance electrochemical sensor for the first time,realizing the repeated use of the same sensor multiple times,greatly reducing the experimental cost and sensor preparation time.At the same time,the establishment of this method expands new approaches for the electrochemical chirality recognition of weak electrochemical activity and non-electrochemically active substances.?2?To achieve the sufficient identification of L-Asp and D-Asp,we used BSA as a chiral selector,and titanium dioxide?TiO2?as an amplifier.BSA/TiO2 composite was introduced with the desired biocompatibility,high stability,and low toxicity effectively amplifying the difference in the molecular interaction between two enantiomers on the sensor.The impedance signals of L-Asp and D-Asp have a good linear relationship in the concentration range of 1 nM to 1000 nM,the detection limits are 0.37 nM and 0.94 nM,respectively,their degree of separation that KL/KD is 1.8.This method was successfully applied to identify the percentage of L-Asp and D-Asp in racemic solution,and laid a good foundation for the simultaneous chiral identification of two enantiomers based on impedance-type electrochemical sensors.The experiment further explored the intermolecular interaction energies and hydrogen bonding forces of D-Asp and L-Asp with solutes and solvents in BSA through quantum calculation.The adsorption sites of the same fragment were calculated based on Boltzmann statistics.The number of D-Asp is more than 10³⁴times that of L-Asp.The theoretical calculation results are consistent with the experimental results,which provides a theoretical basis for the method used to distinguish chiral amino acids.?3?In order to expand the practicality of impedance-type sensors for the recognition of amino acids in weak electrochemical or non-electrochemical activity,the new recognition interface are developed.In the experiment,a newly emerging material MOF was used as the main body,and a chiral source L-histidine?L-His?was synthesized to form a nanocomposite with chiral recognition:L-histidine-ZIF-8?L-His-ZIF-8?,which is used as a membrane material for the sensor to specifically recognize L-glutamic acid?L-Glu?.In the concentration range of 0.1 nM to 50 nM,the interface impedance value of the MOF-based impedance electrochemical sensor increased with the increase of the concentration of L-Glu.An excellent linear relationship was obtained between the impendance signal and the logarithmic concentration of L-Glu,with a detection limit of up to 0.06 nM.Additionally,the recognition mechanism of the target substance L-Glu was analyzed and analyzed from the perspective of molecular structure,which provided a new idea for the synthesis of chiral MOF materials for amino acid enantiomeric recognition.