Temperature-Sensitive Electrochemical Recognition of Tryptophan Enantiomers Based on β-Cyclodextrin Self-Assembled on Poly(L-Glutamic Acid)

A poly(L-glutamic acid)/beta-cyclodextrin (P-L-Glu/beta-CD)-modified glassy carbon electrode (GCE) was prepared by electrochemical polymerization of L-glutamic acid on GCE and subsequent self-assembly of beta-CD onto the obtained P-L-Glu. Electrochemical recognition of tryptophan (Trp) enantiomers with the P-L-Glu/beta-CD was investigated by differential pulse voltammetry (DPV), and the results show that Trp enantiomers can be effectively recognized at the P-L-Glu/beta-CD-modified GCE. It is also interesting to find that temperature plays a crucial role in the enantioselective recognition, which is evidenced by the variable-temperature UV spectra of the inclusion complexes of Tip enantiomers and beta-CD. Under optimum conditions, the oxidation peak current ratio of L-Trp to D-Tip could reach 2.30, which is attributed to the stereoselectivity of beta-CD to the enantiomeric pair of Trp.