A point-of-care diagnostics logic detector based on glucose oxidase immobilized lanthanide functionalized metal–organic frameworks

Abstract

In this work, a novel lanthanide functionalized metal organic framework enzyme (L-MOF-enzyme) composite has been first prepared via a surface attachment strategy between Eu³⁺@UMOF and glucose oxidase (GOx). Here, the Eu³⁺@UMOF can be used as a support for GOx immobilization and also a responsive fluorescent center towards glucose (Glu). The resulting material not only exhibits fascinating luminescence properties based on the ⁵D₀ → ⁷F₂ transition of Eu³⁺ and the catalytic performance of enzymes, but also some advantages of MOF-enzyme composites, including better stability, and great fluorescence selectivity and sensitivity towards Glu (detection limit = 0.2 μM). Besides, the composite exhibited an excellent selectivity and sensitivity towards Glu in serum and urine under room temperature and neutral conditions, which breaks the limitation of specific catalytic conditions of enzymes. Taking all the advantages of the L-MOF-enzyme composite, a point-of care (POC) diagnostics logic detector which can be used for the fluorescence detection of Glu in urine is designed. From the three outputs of the logic detector (L, M and H), we can intuitively realize the self-diagnosis of the three ranges of Glu concentrations that act as the inputs of the detector (0.1 μM–10 μM, 10 μM–10 mM, >10 mM) by the naked eye. The logic detector allows us, especially diabetics, to instantly detect glucose levels in the urine without going to the hospital for complicated inspections. This is the first attempt using L-MOFs combined with GOx to construct a POC diagnostics logic detector for fluorescence detection of Glu.