Dual-Functional CeO₂ Nanozyme-Based Fluorescent Sensing Platform for Chiral Recognition of Arginine and "On-Off-On"...

Nanomaterials with multiple enzyme-like activities offer significant opportunity for constructing multifunctional sensing methods. In this work, a hydrangea flower-like cerium dioxide nanomaterial (CeO₂ NF) with both peroxidase (POD)- and hydrolase-like activities, which was surface-modified by polyvinylpyrrolidone (PVP) in situ, was prepared through an oil bath method. Based on the POD-like activity of CeO₂ NFs, an "on-off" fluorescence method was established for chiral recognition of arginine (Arg) enantiomers. Meanwhile, utilizing the hydrolase-like activity of CeO₂ NFs and their synergistic interaction with alkaline phosphatase (ALP), an "on-off-on" fluorescence method was developed for the detection of p-nitrophenol (p-NP) and ALP. The sensor demonstrated excellent chiral selectivity for Arg enantiomers, with a high enantiomeric factor (ef) of up to 2.48, allowing for the quantitative detection of L-Arg in the range of 770-940 μM, with a limit of detection (LOD) of 26.00 μM. Furthermore, it exhibited high sensitivity for p-NP and ALP detection, with linear ranges of 10.0-84.3 μM and 300-2000 mU/mL, and LODs of 7.07 μM and 200 mU/mL, respectively. Through an enzyme kinetic analysis, fluorescence lifetime measurement, zeta potential analysis, and density functional theory (DFT) calculations, the underlying catalytic and chiral recognition mechanisms were proposed. Finally, the method was validated through the accurate detection of L-Arg, p-NP, and ALP in real samples (rabbit plasma, food-grade amino acid, and water samples).