Ratiometric fluorescence and Nanozyme colorimetry for dual-modality uric acid detection in complex Biosystems

Humans lack urate oxidase (UOX) due to UOX gene mutations, leading to hyperuricemia-related disorders like gout and kidney disease. Accurate uric acid (UA) quantification is therefore vital for diagnosis and management. Conventional methods are often impractical, while popular enzymatic colorimetric assays, though simpler, suffer from cross-reactivity and matrix interference. Nanozymes, such as graphitic carbon nitride (g-C₃N₄), offer robust, cost-effective alternatives; Mn-doping C₃N₄ (Mn-C₃N₄) enhances its uricase-like activity and stability. However, real-world application of Mn-C₃N₄ is still challenged by selectivity issues and matrix effects. To overcome these limitations, we developed a synergistic dual-detection platform integrating Mn-C₃N₄ nanozymes applied together with the ratiometric fluorescent probe MPNVPI. Under blue-light irradiation (460 nm), Mn-C₃N₄ oxidizing UA to generate H₂O₂ triggers an event: nucleophilic cleavage of MPNVPI releases fluorescent HVMI (emission shift: 500 nm to 568 nm). This label-free, dual-modality assay leverages intrinsic optical properties for ultra-sensitive UA quantification in complex serum matrices. It also enables real-time imaging of UA dynamics in RAW 264.7 cells and zebrafish, demonstrating exceptional sensitivity, selectivity, and monitoring capability for diagnostic applications in metabolic disorders.