Voltammetric chiral discrimination of tryptophan using a multilayer nanocomposite with implemented amino-modified beta-cyclodextrin as recognition element

摘要

An electrochemical chiral multilayer nanocomposite was prepared by modifying a glassy carbon electrode (GCE) via oppositecharge adsorption of amino-modified beta-cyclodextrin (NH2-beta-CD), gold-platinum core-shell microspheres (Au@Pts), polyethyleneimine (PEI), and multi-walled carbon nanotubes (MWCNTs). The modified GCE was applied to the enantioselective voltammetric determination of tryprophan (Trp). The Au@Pts enable an effective immobilization of the chiral selector (NH2-beta-CD) and enhance the electrochemical performance. Scanning electron microscopy, transmission electron microscopy, UV-vis spectroscopy, FTIR and electrochemical methods were used to characterize the nanocomposite. Trp enantiomers were then determined by differential pulse voltammetry (DPV) (with a peak potential of +0.7 V vs. Ag/AgCl). The recognition efficiency was expressed by an increase in peak height by about 32% for DPV determinations of L-Trp compared to D-Trp in case of a 5 mM Trp solution of pH 7.0. Response was linear in the 10 mu M to 5.0 mM concentration range, and the limits of detection were 4.3 mu M and 5.6 mu M with electrochemical sensitivity of 43.5 mu A.mu M-1.cm(-2) and 34.6 mu A.mu M-1.cm(-2) for L-Trp and D-Trp, respectively (at S/N = 3).