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). Fe3O4@[email protected]@CuxO 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 Fe3O4@[email protected]@CuxO NPs to display a sharp copper stripping peak at -0.16 V, owning to the electron transfer from Cu+ to Cu2+ and the synergistic electron transfer of Au and Ag double layers. D-AAs can be catalyzed by D-amino acid oxidase (DAAO) to produce H2O2. The autocatalytic oxidation reaction of CuxO shell with the existence of H2O2 induces the decrease of electrochemical signals of Fe3O4@[email protected]@CuxO NPs. Fe3O4@[email protected]@CuxO 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.