Preparation And Recognition Properties Of Graphene Doped Molecularly Imprinted Electrochemical Sensor For Chiral Amino Acids

The chiral amino acid is the basic unit of peptide building blocks of proteins andvital nutrients, has a key role in the life activities of humans and animals. Amino acidenantiomers have different physiological functions. Only L-configuration amino acidsexist in human body and D-amino acid could be absorbed until change into L-aminoacids, excessive intake of D-amino acid may be toxic and even life-threatening；theD-amino acid in the nutrition is not helpful, but has a unique efficacy in the field ofmedicine can be used for the preparation of antibiotics or anticancer drugs. Effectivechiral recognition and detection amino acid enantiomers, helping to reveal thechemical nature of life evolution, broaden the application prospects inbio-pharmaceutics and disease surveillance. Therefore, the developments of efficientchiral recognition methods for amino acid are great significance in promoting thechirality study.Graphene was discovered in2004, becoming a new star in the nanomaterials,showing good application prospects in microelectronics, energy storage, thermalconductivity material and nanocomposites especially in the sensitivity enhancementof sensors due to its excellent physical and chemical properties.Molecular imprinting technique (MIT) thanks to its structural predictability, andgood selectivity, are widely exploited in the fields of chirality recognition andseparation, such as chiral stationary phase of high-performance liquidchromatography and capillary electrophoresis; however, the stationary phases areoften required to derivative and the equipment are expensive, which limited theapplication. Therefore, Applied MIT into the construction of chiral sensors is aconvenient and efficient means for the recognition and detection of chiral substances.In this paper, electrochemical chiral sensors are developed based on theintegration of molecular imprinting technology and sensor technology to achieve arapid identification for two amino acid detection which have electrochemical activity.The main contents as follows:(1)A novel electrochemical sensor was prepared by graphene-chitosan molecularly imprinted film, which casted on the gassy carbon electrode byelectrodeposition, using L-Tryptophan(L-Trp) as the template. Optimize thepreparation conditions of the sensor and discussed the enantioselective recognitionmechanism of tryptophan. Prepared chiral sensors shown favorable performance ofchiral recognition to L/D-tryptophan, L-tryptophan concentration of0.17~25μmol L-1and the oxidation peak current exhibited a good linear relationship with adetection limit of0.04μmol L-1(S/N=3).(2)According to the slight different potential differences in the DPV responses ofL/D-Trp on the MIP sensor, L-Trp-MIP and L-Phe-MIP were prepared，initiallyestablished the scale qualitative approach based on the potential of amino acidisomers. Primary Exploration the mechanism of chiral recognition, to prove feasibleand practical operability design concept.(3)The scanning electron microscope (SEM), atomic force microscope (AFM),X-ray-diffraction spectroscopy (XRD), Fourier transform spectroscopy (FTIR),Raman spectroscopy and electrochemical impedance spectroscopy (EIS) were used tocharacterized the preparation process, and the morphology and structural properties ofthe imprinted films. Through the characterization of morphology and XRD dataprocessing confirmed the chitosan graphene nano-complexes formed on the electrodepoorly ordered along the stacking direction; AFM measured chitosan wrappedgraphene nanosheet thickness of about3nm, Raman spectroscopy gave immediateevidence that the covalent functionalization of GNS with CS did not disrupt theunique π-electronic network of GNS; EIS indicated that the formation of theimprinted membranes imprinted cavities could significantly reduce the interfacialresistance, enhance electronic interface transfer rate, moreover, the differentimpedance value obtained by chiral imprinted membrane interaction with the L/Damino acid proved the chiral recognition ability of the MIP based sensor. Quantumchemical energy analysis discussed the enantioselective recognition of L-tryptophanbased on the theoretical model.