Electroactive NPs and D-amino acids oxidase engineered electrochemical chiral sensor for D-alanine detection

A simple and accurate magnetic electrochemical sensor is developed for the ultrasensitive chiral recognition of D-amino acids (D-AAs). Fe 3 O 4 @Au@Ag@Cu x O nanoparticles (NPs) (x = 1, 2) are controllable prepared and used as the electrochemical beacons. The controllable integration of plasmonic metal NPs, semiconductors and magnetic NPs enables multilayered Fe 3 O 4 @Au@Ag@Cu x O NPs to display a sharp copper stripping peak at -0.16 V, owning to the electron transfer from Cu + to Cu 2+ and the synergistic electron transfer of Au and Ag double layers. D-AAs can be catalyzed by D-amino acid oxidase (DAAO) to produce H 2 O 2 . The autocatalytic oxidation reaction of Cu x O shell with the existence of H 2 O 2 induces the decrease of electrochemical signals of Fe 3 O 4 @Au@Ag@Cu x O NPs. Fe 3 O 4 @Au@Ag@Cu x O NPs served as electrochemical beacons achieve the sensitive and accurate enantioselective recognition of D-alanine (D-Ala) in the range from 100 pM to 10 μM. The limit of detection (LOD) is as low as 52 pM. This developed protocol can be extended to the fabrication of a large set of electroactive labels by the introduction of plasmonic metal NPs with high electron transfer efficiency, for the reliable enantioselective recognition with high sensitivity.