One-step reagentless colorimetric analysis platform of biomineralized Ce-UiO-66 for universal detection of biomarkers

Enzymatic colorimetric analysis system is a sensitive and facile onsite quantitative analysis methodology for disease diagnosis, which undergoes a two-step process: (1) H2O2 generation through catalytic oxidation of biomarkers (glucose, uric acid, xanthine, etc.) by corresponding oxidases and (2) catalytic production of reactive oxygen species from H2O2 by peroxidase/peroxidase-like nanozymes to induce color change of chemical chromogenic agents. However, natural enzymes and chemical chromogenic agents are easily oxidized/degraded under harsh environments, thereby being restricted to well-equipped laboratories and seriously limiting their applications. Herein, natural oxidase-encapsulated Ce-UiO-66 (oxidase@Ce-UiO-66), prepared via a facile one-step approach under mild conditions, was exploited to construct a reagentless colorimetric smartphone analysis platform for quantitative analysis of various disease biomarkers. Ce-UiO-66 as carrier of oxidases not only enhanced their stability under long-term storage but also preserved their activity for H2O2 generation through catalytic oxidation of biomarkers under various environments. Subsequently, Ce-UiO-66 served as a dose-dependent chromogenic agent of H2O2 due to the Ce-UiO-66-to-CeO2 phase transition, leading an apparent color evolution from white into orange. Based on the corresponding oxidase@Ce-UiO-66, the smartphone-enabled colorimetric analytic system was developed to achieve a facile, sensitive, and specific onsite detection of glucose (limit of detection (LOD): 35 μM and a wide range of 39–20,000 μM), uric acid (LOD: 21 μM and a wide range of 26–3400 μM), and xanthine (LOD: 3.9 μM and a wide range of 15.6–500 μM), giving their promises for clinic diagnosis.