Sensing Study For Selective Detection Of L-tryptophan And L-tyrosine Based On Ultrastructured Copper-based Materials

Tyrosine(Tyr)and tryptophan(Trp)are indispensable amino acids in human and animal metabolism,whose excessive consumption in the body will lead to metabolic disorders,resulting in a series of diseases.Since the two amino acids coexist in the body and have similar properties,the oxidation peak positions of them are severely overlapped.Thus,how to effectively avoid interference and achieve highly selective detection of single or two amino acids is still a huge challenge nowadays.Based on the development of new nanomaterials,ultrastructure copper-based nanomaterials have been widely used due to their excellent quantum size effect,biocompatibility,high specific surface area,and strong catalytic performance.In order to solve the problems of high selectivity and high sensitivity detection for tyrosine(Tyr)and tryptophan(Trp),two ultrastructure copper-based nanomaterials were prepared in this paper,which were fabricated into composite membrane modified electrodes through layer-by-layer self-assembly,achieving the high-selectivity detection of single or two amino acids and which is expected to be used for early diagnosis of medical diseases and food nutrition analysis of great research significance.The main research contents are as follows:1.A series of Pt-Cu bimetallic nanomaterials were prepared by one-pot method,and a novel electrochemical method for sensitive determination of L-Trp was constructed based on Pt-Cu bimetallic nanocrystalline composite film with optimized structure and properties.Ultrastructural copper-based alloy nanomaterials have excellent catalytic and electrical properties.Due to the excellent catalytic and electrical properties of ultrastructure copper-based alloy nanomaterials,a series of Pt-Cu bimetallic nanocrystals were prepared by a bimetallic precursor synthesis strategy,and investigated the effect of different reducing agents on the growth of Pt-Cu bimetallic nanocrystals.The results show that when oleylamine(OM)and L-ascorbic acid(L-AA)are used as reducing agents,the prepared material is a prismatic dodecahedron with an edge length of 23.02 ± 4.78 nm.In addition,electrochemical experiments show that the increase of copper content can significantly improve its electrical conductivity and catalytic activity.Then,the PtCu49/Nafion/GQDs sensing film was constructed by using the optimized structure and performance of PtCu49 nanomaterials combined with imidazole modified graphene quantum dots(GQDs),which has good response performance to L-Trp with the linear range of 0.600～30.0 μmol/L,and the detection limit is 0.122 μmol/L.Moreover,the sensor has excellent anti-interference ability and reproducibility,which has been successfully applied to the determination of L-Trp in pig serum samples,and the obtained results are consistent with the high performance liquid chromatography data.Therefore,the sensor based on ultrastructure Pt-Cu bimetallic nanomaterials has a great application prospect in the field of life science analysis.2.An electrochemical analysis method for simultaneous detection of L-Trp and L-Tyr based on hexagonal CuS nanocrystalline composite film was established with the effect of aldehyde media.In this paper,two kinds of CuS nanomaterials with different sizes were synthesized by changing the adding order of precursors.The large-sized hexagonal CuS nanocrystals were obtained by adding sulfur powder,oleylamine,and oleic acid via a step-by-step method,and the side length is 89.43 ± 9.22 nm with a thickness of 70.08 ± 10.95 nm.Small-sized hexagonal CuS nanocrystals were obtained by adding the mixture of sulfur powder,oleylamine and oleic acid,and the side length is 15.08 ± 2.10 nm with a thickness of 5.27 ± 0.74 nm.Then,two modified electrodes(h-CuS@CS/A-MWCNTs/GCE)were prepared by combining CuS nanocrystals with chitosan(CS)and acidified carbon nanotubes(A-MWCNTs).The modified electrodes were investigated under the mediation of formaldehyde for the response of L-Trp and L-Tyr,and the results show that the performance of small size CuS is significantly better than that of large size CuS nanocrystal,as well as realizing the separation and detection of L-Trp and L-Tyr with a peak potential difference ofΔE=220 mV.The reaction mechanism between formaldehyde and amino acids was further explored through mass spectrometry(MS)and UV-Vis spectrophotometry,certificating that the product(2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole-3-carboxylic acid)was generated due to the Pictet-Spenglar reaction between formaldehyde and L-Trp,while L-Tyr does not react with formaldehyde.Thus,the separation of L-Trp and L-Tyr is achieved in view of the different reaction products of amino acids and formaldehyde.Furthermore,the sensor has a good linear range and excellent anti-interference for the determination of L-Trp and L-Tyr,and the new strategy for selective detection of L-Trp and L-Tyr based on formaldehyde-mediated action is simultaneously applicable to other four sensing interfaces,fully confirming that this method can become a feasible and general sensing platform for detection of L-Trp and L-Tyr in the field of biological sciences.