Construction Of Polymer Chiral Interface For Electrochemical Recognition Of Amino Acid Enantiomers

Chirality is a common phenomenon in life.Chiral substances have similar physical and chemical properties,but have different or even opposite pharmacological and biological activities.Therefore,it is of great practical significance to develop an effective chiral recognition platform to detect enantiomers.In the application of electrochemistry in chiral recognition,the key is to construct an electrochemical chiral interface.The chiral interface provides chiral microenvironment or chiral center by chiral selectors,but except for a few conductive substances,most chiral selectors are non-conductive,which is not conducive to electrochemical recognition of amino acid enantiomers.Therefore,in this study,chiral selective agents and electrochemically responsive substances（such as ferrocene,nanoparticles,ionic liquids（IL）,etc.）were combined to construct a more sensitive chiral sensing interface,and to realize the electrochemical recognition of amino acid enantiomers.The main research contents and results are as follows:（1）The β-CD@PEI-Fc chiral interface was prepared based on the supramolecular host-guest interaction between Ferrocene（Fc）grafted polyethyleneimine（PEI-Fc）and chiralβ-cyclodextrin.SEM results show thatβ-CD@PEI-Fc interface has a regular spatial structure,which can effectively distinguish tryptophan（Trp）enantiomers.More interestingly,theβ-CD@PEI-Fc/GCE exhibited chiral recognition of D-Trp and L-Trp via water contact angle measurements.Under the optimal conditions,differential pulse voltammetry（DPV）shows that the current ratio（I_D/I_L）of Trp enantiomers can reach 2.84 at 15℃.The chiral interface can be used to quickly determine the proportion of isomers in Trp racemic solution,which is of great significance for chiral recognition in racemic mixture of chiral compounds.（2）The chitosan（CS）/polyacrylic acid（PAA）multilayer film（（CS/PAA）n）was prepared by layer-by-layer self-assembly technique,which was compounded with ionic liquid（IL）to prepare（CS/PAA）_n@IL multilayer films chiral interface.As a result,the chiral recognition efficiency of the（CS/PAA）_n@IL chiral interface for the tryptophan enantiomer is significantly increased,and the current ratio（I_D/I_L）is 5.19.In the concentration range of0.005 m M-0.15 m M,（CS/PAA）_2.5@IL/GCE chiral interface demosntrated a good linear relationship with its peak current in D-Trp and L-Trp enantiomers solutions.This is also useful to quickly identify the ratio of the Trp enantiomer mixed solution.（3）We used PEI-Fc for in situ synthesis of gold and silver nanoparticles（Au、Ag NPs）.The layer of the PEI-Fc@Au NPs-D-Trp was used as base layer and then puts into the mixed solution of D-Trp and L-Trp with the presence of Cu²⁺.Since gold/silver nanoparticles（Au,Ag NPs）and Cu²⁺can bind to D-Trp preferentially,Ag NPs@D-Trp is linked to the electrode surface through Cu²⁺to form a network structure.Compared with Ag NPs@L-Trp,it greatly increases the amount of Ag NPs on the electrode surface.The oxidation of Ag NPs was also used to distinguish Trp enantiomers by indirect determination.The results show that this method amplifies the electrochemical recognition signal of the Trp enantiomers,and the current ratio I_D/I_L is as high as 7.12.