Chiral PEDOT-Based Enantioselective Electrode Modification Material for Chiral Electrochemical Sensing: Mechanism and Model of Chiral Recognition

The development of electrochemical methods for enantioselective recognition is a focus of research in pharmaceuticals and biotechnology. In this study, a pair of water-soluble chiral 3,4-ethylenedioxythiophene (EDOT) derivatives, (R)-2 '-hydroxymethyl-3,4-ethylenedioxythiophene ((R)-EDTM) and (S)-2 '-hydroxymethyl-3,4-ethylenedioxythiophene ((S)-EDTM), were synthesized and electrodeposited on the surface of a glassy carbon electrode (GCE) via current-time (I-t) polymerization in an aqueous LiClO4 electrolyte. These chiral PEDOT polymers were used to fabricate chiral sensors and to investigate the enantioselective recognition of D-/L-3,4-dihydroxyphenylalanine, D-/L-tryptophan, and (R)-/(S)-propranolol enantiomers, respectively. The results indicated that the (R)-PEDTM/GCE sensor showed a higher peak current response toward the levo or (S) forms of the tested enantiomers, while the opposite phenomenon occurred for (S)-PEDTM/GCE. The mechanism of the stereospecific interaction between these enantiomers and the chiral polymers was determined. Therefore, a model of the chiral recognition by the chiral conducting polymer electrodes and an electrochemical method was proposed. The chirality of the enantiomers was confirmed by two parameters: the chirality of the electrode and the peak current response. These findings pave the way for the application of chiral PEDOT as electrode modification material in the electrochemical chiral recognition field.