Yolk-shell structured nanoreactor Au@Co3O4/CeO2@mSiO2 with superior peroxidase-like activity as nanozyme for ultra-sensitive colorimetric biosensing.

For yolk-shell structured nanoreactors, multiple active components can be precisely positioned on core and/or shell that can afford more exposed accessible active sites, and the internal voids can guarantee sufficient contact of reactants and catalysts. In this work, a unique yolk-shell structured nanoreactor Au@Co3O4/CeO2@mSiO2 was fabricated and applied as nanozyme for biosensing. The Au@Co3O4/CeO2@mSiO2 exhibited superior peroxidase-like activity with a lower Michaelis constant (Km) and a higher affinity to H2O2. The enhanced peroxidase-like activity was attributed to the unique structure and the synergistic effects between the multiple active components. Colorimetric essays were developed based on Au@Co3O4/CeO2@mSiO2 for the ultra-sensitive sensing of glucose in the range of 3.9 nM-1.03 mM with the limit of detection as low as 3.2 nM. In the detection of glucose-6-phosphate dehydrogenase (G6PD), the cooperation between G6PD and Au@Co3O4/CeO2@mSiO2 triggered the redox cycling between NAD+ and NADH, thereby achieving the amplification of the signal and enhancing the sensitivity of the assay. The assay showed superior performance as compared to other methods with linear response of 5.0 × 10-3-15 mU mL-1 and lower detection limit of 3.6 × 10-3 mU mL-1. The fabricated novel multi-enzyme catalytical cascade reaction system allowed rapid and sensitive biodetection, demonstrating its potential in biosensors and biomedical applications.