One-pot synthesis of gold-copper nanoparticles mediated by silk fibroin peptides: Peroxidase-like properties and its application in antioxidant detection

Abstract

SFP@Au-CuNPs were synthesized by the one-pot reduction method using silk fibroin peptides as reductants and stabilizers. The synthesis process was simple, safe, and environmentally friendly. The synthesized SFP@Au-CuNPs showed effective peroxidase mimicking activity through colorimetric analysis and had a catalytic effect. The reaction pH value, temperature, time, and concentration were optimized to determine the best method for achieving the inherent catalytic activity in practical application. According to the double reciprocal curve, the Michaelis–Menten constants of TMB and H2O2 substrates were calculated to study the affinity of the SFP@Au-CuNPs using TMB and H2O2 substrates. The Km of H2O2 was 0.240 mM, and the TMB was 0.040 mM. SFP@Au-CuNPs had a strong affinity for the H2O2 and TMB substrates. The peroxidase-like characteristics of the SFP@Au-CuNPs were used to detect antioxidants, in which ascorbic acid LOD was 0.059 μM, gallic acid LOD was 0.010 μM, and LOD was 0.040 μM. Colorimetric analysis using UV-spectrophotometer was used to observe the color changes. The R2 values of the ascorbic acid, gallic acid, and l-cysteine were 0.998, 0.996, and 0.990, respectively, indicating that the curve has a good linear relationship in the detection range and the assay was successfully used to evaluate the antioxidant content of real fruits. This study provides a broader prospect for the preparation of nanozymes for relevant applications.