Design And Application Of Novel Electrochemical Sensors For Glutamic Acid

L-Glutamate(L-Glu)is one of the 20 standard amino acids used by all organisms.It is considered the primary neurotransmitter in the mammalian brain that facilitates normal brain function.It is also found in many food products in the form of monosodium glutamate(MSG),which is added to enhance flavour.Due to the important role of L-Glu in nutrition,clinical application and food proeessing industry,the rapid and sensitive detection of this amino acid in food as well as in organism like serum is crucial to the development of medicine,pathology as well as that of food and drug production or processing industries.A lot of researches on methods for detection of L-Glu have increased significantly over the last decade.However,electrochemical sensing offer a method of analysis which has the advantages such as fast,user friendly,low cost,smart instruments,good selectivity,high sensitivity compared with classical techniques.Therefore,electrochemical biosensors for the detection of L-Glu have been of great research interest in recent years.This paper mainly discussed the preparation of novel L-Glu electrochemical sensors through the molecular imprinted technology as well as different nanomaterials.And the sensors can be applied to the determination of pig serums.The surface morphologies of different electrodes were characterized by means of scanning electron microscopy(SEM),transmission electron microscopy(TEM),cyclic voltammetry(CV),and electrochemical impedance spectroscopy(EIS).The linearity relationship curve was established by differential pulse voltammetry(DPV).Moreover the properties of selectivity,stability,repeatability and recovery were also investigated.The main research content is as follow:In the second chapter,a molecularly imprinted polymer(MIP)based glutamic acid sensor with multi-walled carbon nanotubes(MWCNTs)decorated on a glass carbon electrode(GCE),named as MIP/MWCNTs/GCE was developed in this work.It was prepared through the electropolymerization using L-glutamic acid(L-Glu)as a template and 4,6-diaminoreorcion as the monomer,then the template molecule was eluted with acetonitrile/formic acid(1:1).The reaction conditions were optimized as electrochemical polymerization with 23 cycles,pH 5.0,template/monmer=1:4,elution time of 2 min.The prepared materials and molecularly imprinted polymer were characterized by using scanning electron microscope(SEM)and transmission electron microscope(TEM)as well as electrochemical methods.The electrochemical properties of different electrodes were investigated via differential pulse voltammetry(DPV),showing that the electrode of MIP/MWCNTs/GCE exhibited excellent catalytic oxidation activity to L-Glu.And a good linear response of the peak currents were observed for L-Glu concentrations ranging from 1.00x10-8 sto 1.00x10-5 mol/L(R2=0.9923),with a detection limit of 5.13×109 mol/L(S/N=3).The electrode performed excellent selectivity,high sensitivity and good stability,which was successfully applied to the detection of L-Glu in pig serum samples with a recovery rate of 97.40%?104.0%.This work is of geat significant that may provide a new way to the determination of L-Glu in the fields of animal nutrition and biomedical enginerring.In the third chapter,a poly tryptophan(PTrp)film modified carbon nanotubes electrode(PTrp/MWCNTs/GCE)was prepared through the electropolymerization for sensitive deternination of L-glutamate(L-Glu).The morphologies of electrode surface were characterized by transmission electron microscopy(TEM).The electrochemical behaviors and reaction mechanism of L-Glu were investigated through cyclic voltammetry(CV)and differential pulse voltammetry(DPV),indicating that PTrp/MWCNTs/GCE exhibited excellent electrocatalytic oxidation activity to L-Glu in 0.10 mol/L CH3COOH?CH3COONa buffer solution(pH=3.90).The peak currents of the modified electrode showed a good linear relationship with the concentration of L-Glu in the range of 5.000×l0-8?1.500×10-5 mol/L with a detection limit of 2.580×10-8 mol/L(S/N=3).In partieular,this electrode displayed high selectivity,good stability and reproducibility,which can be successfully applied to detection of L-Glu in pork serum samples with recoveries of 94.83%?104.5%,making it suitable for the analysis of animal breeding field.In the fourth chapter,the adsorption models between poly L-tryptophan,poly L-aspartic acid,poly L-lysine and other poly amino acid compounds with L-glutamic acid were established using Materials Studio 8.0 software.After optimizing the structure by Geometry Optimization,the adsorption energy was calculated by using Dynamics under the conditions of 298 K,1 fs,2000 PS and 20000 stages.The results showed that the adsorption energies of poly L-tryptophan is-402.775 kcal/mol.Compared with other amino acids,poly L-tryptophan has stronger adsorption capacity for L-glutamic acid,and it is more suitable as electrode material.