Amperometric sensing of L-phenylalanine using a gold electrode modified with a metal organic framework, a molecularly imprinted polymer, and beta-cyclodextrin-functionalized gold nanoparticles

摘要

The authors describe the construction of a molecularly imprinted electrochemical sensor for enantiomeric recognition of L-phenylalanine (L-Phe). Firstly, thiolated beta-cyclodextrin (beta-CD) and L-cysteine were used to functionalize gold nanoparticles via gold-thiol chemistry and to act as a basis for the formation of a microporous metal-organic framework (MOF). AMOF imprinted polymer was deposited on the functionalized gold nanoparticles by electropolymerization in the presence of the template L-Phe and the functional monomer 4-aminothiophenol. The modified electrode was characterized by cyclic voltammetry and electrochemical impedance spectroscopy in the presence of hexacyanoferrate acting as the redox probe. The electrode, operated best at 0.2 V vs. Ag/AgCl, exhibits excellent selectivity for L-Phe, with an enantioselectivity coefficient of 2.12 over D-Phe. In addition to its good enantiomeric selectivity, the sensor has a 0.33 pM detection limit which is much lower than that reported for other electrodes. The sensor has been successfully applied to the analysis of urine spiked with L-Phe.