Rational Development of Co‐Doped Mesoporous Ceria with High Peroxidase‐Mimicking Activity at Neutral pH for Paper‐Based Colorimetric Detection of Multiple Biomarkers

Abstract Peroxidase‐mimicking nanozymes have been extensively studied, however, their application is limited by the requirement for an acidic pH. Herein, the development of Co‐doped mesoporous cerium oxide (Co‐m‐ceria) is reported, which operates optimally at a near‐neutral pH and exhibits a peroxidase‐like catalytic efficiency that is 600‐times higher than that of pristine m‐ceria. Density functional theory (DFT) calculations for the application of pristine and various metal‐doped m‐ceria in peroxidase‐like reactions under different pH environments are conducted to select Co as the appropriate dopant. The high peroxidase‐like activity of Co‐m‐ceria under neutral conditions and its mesoporous nature enable its application in a one‐pot cascade reaction system, wherein biomarkers of oxidative enzymes can be detected without altering the pH. Five different oxidative enzymes are immobilized in the pores of Co‐m‐ceria at high loadings, followed by incorporation of the enzyme‐containing Co‐m‐ceria in paper microfluidic devices for the convenient and simultaneous detection of multiple biomarkers. The Co‐m‐ceria‐incorporated paper microfluidic device enables the selective and sensitive determination of multiple biomarkers using a smartphone‐acquired image. This study demonstrates the potential of the rational design of nanozymes and their application in paper microfluidic devices, laying the groundwork for future applications of nanozymes in point‐of‐care testing environments.