A highly stable terbium metal−organic framework as a fluorescence turn-off sensor for glutamic acid in human urine and serum

Abstract

Glutamic acid (Glu) is a biomarker of some neuropathological diseases, whose detection is of significance in early medical diagnosis. A 3D terbium metal-organic framework (Tb-ddb) is constructed from 1,3-di(3′,5′-dicarboxylphenyl)benzene (H4ddb) with Tb3+, displaying the 5D4 → 7Fj (j = 6-3) transfers of Tb(Ⅲ) at 490, 543, 584, and 621 nm. Tb-ddb has a high stability in water or common organic solvents. The sensitivity test shows a linear fitting equation of I0/I = 0.00443·CGlu + 0.93563 with LOD = 1.40 μM at CGlu = 0–500 μM. The detection performance of Tb-ddb is not affected by seven interferents of amino acids. High durability is supported by the stable emission intensities at 543 nm of blank Tb-ddb and Tb-ddb/Glu suspensions in five fluorescence quenching-recovery cycles. The returned CGlu close to the set CGlu and the recoveries around 100% demonstrate Tb-ddb sensing Glu in human urine and serum is reliable. The linear relationship between green value of the Tb-ddb strip and CGlu can realize the on-site Glu detection. Tb-ddb can be regarded as a promising fluorescence turn-off sensor to Glu with high sensitivity, selectivity and durability.