Rational design of Ag-doped MnFe2O4/HNTs for peroxidase-mimicking activity and colorimetric sensing of uric acid in human serum.

Mimicking enzyme have significantly advanced sensing assays by replicating native enzyme functions, yet achieving both high catalytic activity and easy recyclability remains a challenge. In this study, Ag-doped MnFe₂O₄/halloysite nanotubes (HNTs) were rationally designed as a novel nanozyme by depositing in-situ Ag and MnFe₂O₄ nanoparticles onto HNTs. The resulting nanocomposite exhibited excellent peroxidase-like activity along with magnetic properties. Leveraging these features, a highly efficient and sensitive colorimetric system for detecting uric acid (UA) was developed. The Ag-doped MnFe₂O₄/HNTs catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of H₂O₂, causing a color change from colorless to blue. The system showed a linear absorbance response to UA concentrations ranging from 1 to 20 μM, with a detection limit of 59 nM. Mechanistic studies revealed that reactive oxygen species intermediates (¹O₂) were generated through the decomposition of H₂O₂, leading to peroxidase-like activity in the Ag-doped MnFe₂O₄/HNTs. The assay was successfully applied to detect UA in human serum with recoveries over 99.68 %. This study indicates the successful application of Ag-doped MnFe₂O₄/HNTs for colorimetric UA detection in human serum. This research introduces a novel approach for designing recyclable, high-performance mimicking enzyme and establishes an effective colorimetric sensing platform for UA detection in human serum.