Choline is an important molecule in monitoring food safety and infant nutrition. Here, we report Ce nanogels synthesized by atom transfer radical polymerization (ATRP) employing Ce-coordinated acryloyl-lysine polymer brushes (Ce@SiO2 NGs) as highly efficient cascade nanozymes for colorimetric detection of choline. The synthesized Ce@SiO2 NGs demonstrated remarkable peroxidase-like activity with a porous exterior, which are essential to entrap choline oxidase (COx) to yield COx@Ce@SiO2 NGs and construct a cascade reaction system to detect choline. Immobilized COx catalyzed the oxidation of choline in food samples to produce H2O2, which subsequently induced the oxidation of chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) to produce blue color signals. This method enabled the selective and sensitive detection of target choline with a satisfactory linear range of 4-400 μM, which is sufficient to analyze foodborne choline. The practical utility of the COx@Ce@SiO2 NG-based assay was successfully validated to determine choline spiked in commercially available milk and infant formula with high accuracy and precision values. This approach provides a simple and affordable method of choline detection and has the potential to lead to more developments in ATRP-based nanozymes for diverse biosensing applications.
Keywords: ATRP-based nanogels; cascade reaction; choline detection; food safety; peroxidase-like nanozymes.