A highly sensitive Zr-MOF mediated multi-enzyme cascade platform for the colorimetric and fluorescent dual-signal determination of sarcosine

Abstract

Herein, a highly sensitive detection platform for the dual-mode determination of sarcosine by fluorescence and colorimetry was constructed based on zirconium-based metal organic frameworks (Zr-MOFs) with multi-enzyme immobilization. Zr-MOFs with peroxidase-mimicking activity were firstly prepared by a solvothermal method, and sarcosine oxidase (SOX) and horseradish peroxidase (HRP) were simultaneously encapsulated in the Zr-MOFs to form the Zr-MOFs@SOX@HRP composite. Oxidation of sarcosine could be catalyzed by the SOX in the Zr-MOFs@SOX@HRP composite to generate hydrogen peroxide (H₂O₂). The generated H₂O₂ was decomposed through the synergistic catalysis by Zr-MOFs and HRP to generate free radicals that could oxidize the chromogenic substrate p-phenylenediamine (PPD) to produce oxPPD. The oxPPD generated could quench the fluorescence of carbon dots at 510 nm via the internal filtering effect (IFE). The amount of sarcosine could be sensitively detected by monitoring the changes of the colorimetric and fluorescence signals, with detection limits of 0.44 μM and 0.21 μM, respectively. Thus, the dual-mode detection of sarcosine by fluorescence and colorimetry through a Zr-MOF-mediated cascade reaction system was realized. The method was applied to the determination of sarcosine in the urine of healthy individuals as well as in the urine of prostate cancer patients with satisfactory results, demonstrating its enormous potential for predicting prostate cancer disease.