Bimetallic nanoparticles with enhanced peroxidase-like activity and enantioselectivity for colorimetric discrimination of D,L-tryptophan

Abstract

Chiral recognition by monometallic nanozymes has received extensive attention. However, determining the basis of the chiral identification properties of bimetallic nanozymes is critical and poses challenges. Herein, by leveraging L-tryptophan (LW), L-histidine (LH), L-proline, L-tyrosine and L-dipeptide (LWLH) as chiral ligands, four kinds of bimetallic nanozymes were fabricated based on gold nanoparticles (AuNPs) modified onto the surface of copper nanoparticles (LWLH@CuNPs) . The substrate 3,3′,5,5′-tetramethylbenzidine (TMB) was efficiently oxidized to yield blue oxTMB in these nanozymes-H₂O₂ systems, verifying their peroxidase-like activity that resulted from the synergistic effect of the bimetallic nanozymes. Notably, in the presence of D,L-tryptophan (D,L-Trp), the visible absorbance of oxTMB at 650 nm in the LW@AuNPs-LWLH@CuNPs-TMB-H₂O₂ system was significantly altered, in the contrast with the other three bimetallic nanozymes and monometallic LWLH@CuNPs. The mechanism underpinning the enhanced chiral discrimination ability of LW@AuNPs-LWLH@CuNPs was based on hydrogen-bonding and electron transfer. Furthermore, the proposed LW@AuNPs-LWLH@CuNPs nanozymes were applied to measure L-Trp in saliva samples. This study deepens understanding of the advantages of incorporating AuNPs onto CuNPs, specifically, improving the peroxidase-like activity of bimetallic nanozymes and highlighting their potential for colorimetric chiral recognition of D,L-amino acids.