Activity-tunable bimetallic iron-cobalt nanoflowers integrated with smartphones for rapid detection of human uric acid.

BACKGROUND: Uric acid (UA), a key biomarker linked to diseases like gout and Alzheimer's, can be detected using nanozyme technology. Developing sensitive nanozyme-based biosensors for UA is therefore crucial for early disease diagnosis and prevention. RESULTS: In this work, activity-tunable nanoflowers (FeCo NFs) were successfully synthesized with different metal ratios demonstrated varying the peroxidase-like and oxidase activities. A dual-mode assay (ratiometric fluorescence and colorimetric) based on functionalized with amino groups (FeCo NFs-NH2) was proposed with LOD as low as 0.41 μM and 0.31 μM, respectively. Electron spin resonance measurements revealed that the difference in the catalytic activity of nanozymes with different metal ratios stems from their varying •OH generation capabilities. Furthermore, the fluorescence of FeCo NFs-NH2 could be quenched by 2,3-diaminophenazine (DAP) via inner filter effect and photoinduced electron transfer, which was investigated in detail with the aid of the Stern-Volmer and Parker equations. Finally, a smartphone-based detection platform was developed, enabling portable, instrument-free, and sensitive detection of UA. SIGNIFICANCE: This work fully unites and utilizes the advantages of multifunctional probe and dual-channel detection for reliable serodiagnosis and related diseases evaluation. Moreover, this in-depth study has made guiding progress in the regulation of catalytic activity of metal nanoenzymes, especially in the regulation of oxidase activity and peroxidase activity.