Electroactive Au@Ag Nanoparticle Assembly Driven Signal Amplification for Ultrasensitive Chiral Recognition of d‑/l‑Trp

A novel ingenious and ultrasensitive chiral electrochemical transducer is proposed for tryptophan (Trp) isomer detection by using electroactive Au@Ag NPs as electrochemical tags. Moreover, the large binding constant of d-Trp on NPs and strong interaction between d-Trp and Cu2+ cause electroactive Au@Ag NP to assemble on the electrode, generating strong differential pulse voltammetry (DPV) signals from the oxidation of Ag0 to Ag+. In sharp contrast to d-Trp, l-Trp leads to the assembly of Au@Ag NP oligomers on the electrode, resulting in a weak DPV signal. The distinct DPV responses enable the developed electrochemical chiral transducer for the sensitive and accurate quantification of d-/l-Trp. The limit of detection (LOD) is 1.21 pM for d-Trp. This established electrochemical chiral sensor also achieves the specific determination of enantiomeric excess. In comparison to other reported approaches, this proposed electrochemical chiral sensor excels by its sensitivity, simplicity, and good availability of electroactive Au@Ag NP assemblies. Target-induced colorimetric assays can be converted into electrochemical assays for the dual signal amplification in the field of ultrasensitive enantioselective chiral discrimination.