Visible and Ultraviolet Dual-Readout Detection of Cu(II) in Preserved Vegetables Based on Self-Assembly and Peroxidase Simulation Properties of Mb-AuNPs

Abstract

Cu(II) adulteration in preserved vegetables by unreliable producers to increase their visual appeal or compensate for natural colour changes is most common. Methanobactin (Mb) is a Cu(II)-coordinated peptide, which plays crucial role in Cu(II) capture and absorption and the catalysis of Cu(II)-containing methane monooxygenase in methanotrophs. In this study, Mb-functionalized gold nanoparticles (Mb-AuNPs) was applied to develop a dual readout colorimetric detection for Cu(II) adulteration in preserved vegetables. In the presence of Cu(II), Mb-AuNPs was assembled into nanocluster driven by Cu(II)/Mb coordination, and the assembly process was monitored by the visible spectrum on the variation of surface plasmon resonance peak. The results showed that, Mb-AuNPs possessed excellent peroxidase-like activity after Cu(II) coordination. In the presence of Mb-AuNPs, the amount of Cu(II) obviously affected the rate of hydroquinone oxidation by H2O2 and the change of A246. The visible and ultraviolet dual-readout detection system containing Mb-AuNPs, hydroquinone and H2O2 exhibited high sensitivity and selectivity for Cu(II). The linear range of visible and UV detection towards Cu(II) was 0.05–0.4 μmol/L, the limit of detection were 37.50 nmol/L and 4.48 nmol/L, respectively. In conclusion, the Cu(II) coordination driven Mb-AuNPs assembly makes it able to detect Cu(II) adulteration in preserved vegetables by dual channel methods to eliminate the occurrence of false positives and improve the accuracy of measurement results. Such non-spatially separated Mb-AuNPs assembly and it catalyzed hydroquinone oxidation dual channel readout was simple, fast, reliable and significantly facilitated the detection efficiency of Cu(II).