An electrochemical chiral sensor based on competitive host–guest interaction for the discrimination of electroinactive amino acids

A novel electrochemical chiral sensor has been designed based on the principle of competitive host–guest interaction and utilized for the discrimination of electroinactive proline (Pro) isomers. Electroactive methylene blue (MB) was used as the signal probe, which was combined with multi-walled carbon nanotubes (MWCNTs)-decorated β-cyclodextrin (β-CD), via host–guest interaction, where the oxidation peak currents of MB decreased after isomers of Pro were combined with the MWCNTs-β-CD via a competitive host–guest interaction. Due to the steric configuration of L-Pro matching the cavity of β-CD, more L-Pro than D-Pro was combined with MWCNTs-β-CD, resulting in a more pronounced decrease of MB peak currents. Therefore, the isomers of Pro could be discriminated. Besides Pro, the isomers of electroinactive histidine (His) could also be discriminated with the chiral sensor. In addition, the contents of L-Pro in non-racemic mixtures could be detected with the developed chiral sensor.