Highly Stable Lanthanide Metal–Organic Framework as an Internal Calibrated Luminescent Sensor for Glutamic Acid, a Neuropathy Biomarker

Abstract

Glutamic acid (Glu) is the most abundant excitatory neurotransmitter in the central nervous system, and an elevated level of Glu may indicate some neuropathological diseases. Herein, three isomorphic microporous lanthanide metal−organic frameworks (MOFs) [(CH 3 ) 2 NH 2 ] 2 [Ln 6 (μ 3 -OH) 8 (BDC-OH) 6 (H 2 O) 6 ]•(solv) x (ZJU-168; ZJU = Zhejiang University, H 2 BDC-OH = 2-hydroxyterephthalic acid, Ln = Eu, Tb, Gd) were designed for the detection of Glu. ZJU-168(Eu) and ZJU-168(Tb) suspensions simultaneously produce the characteristic emission bands of both lanthanide ions and ligands. When ZJU-168(Eu) and ZJU-168(Tb) suspensions exposed to Glu, the fluorescence intensity of ligands increases while the emission of lanthanide ions is almost unchanged. By utilizing the emission of ligands as the detected signal and the emission of lanthanide ions as the internal reference, an internal calibrated fluorescence sensor for Glu was obtained. There is a good linear relationship between fluorescence intensity ratio and Glu concentration in a wide range with the detection limit of 3.6 μM for ZJU-168(Tb) and 4.3 μM for ZJU-168(Eu). Major compounds present in blood plasma have no interference for the detection of Glu. Furthermore, a convenient analytical device based on a one-to-two logic gate was constructed for monitoring Glu. These establish ZJU-168(Tb) as a potential turn-on, ratiometric, and colorimetric fluorescent sensor for practical detection of Glu.

Our journey of developing dual‐emitting metal‐organic framework‐based fluorescent sensors

“…isomorphic MOFs ZJU-168(Eu), ZJU-168(Tb), and ZJU-168(Gd) were designed for Glu detection (Figure 9a). [43] The suspensions of ZJU-168(Eu) and ZJU-168(Tb) in water produce both the characteristic emission bands of lanthanide ions and ligands, while that of ZJU-168(Gd) only presents ligand emission. When ZJU-168(Eu) and ZJU-168(Tb) suspensions are exposed to Glu, the emission intensity of ligands increases while that of lanthanide ions hardly changes (Figure 9b).…”

“…Glutamic acid (Glu) is the most abundant excitatory neurotransmitter and an elevated level of Glu may indicate some neuropathological diseases. Recently, by immobilizing −OH functional groups in framework act as specific sites, three isomorphic MOFs ZJU‐168(Eu), ZJU‐168(Tb), and ZJU‐168(Gd) were designed for Glu detection (Figure 9a) [43] . The suspensions of ZJU‐168(Eu) and ZJU‐168(Tb) in water produce both the characteristic emission bands of lanthanide ions and ligands, while that of ZJU‐168(Gd) only presents ligand emission.…”

Mono- and Mixed Metal Complexes of Eu3+, Gd3+, and Tb3+ with a Diketone, Bearing Pyrazole Moiety and CHF2-Group: Structure, Color Tuning, and Kinetics of Energy Transfer between Lanthanide Ions

“…The unique luminescent properties of lanthanide ions are actively studied due to the possibility of their use in emitting materials [ 1 , 2 , 3 ], biovisualization [ 4 , 5 , 6 , 7 ], banknote protection [ 8 ] and in creating sensing materials [ 9 , 10 , 11 ].…”

Dual-Function Lanthanide–Organic Frameworks Based on a Zwitterionic Ligand as a Ratiometric Thermometer and a Selective Sensor for Nitroaromatic Explosives

“…Lanthanide metal–organic frameworks (Ln-MOFs), combining the excellent luminescence of lanthanide ions and structural tunability of MOFs, have been extensively exploited as emitters and chemical sensors. − Due to the unique sharp emission, high luminescence quantum yield, long lifetime, and large Stokes shift, Ln-MOFs have great potential as sensory materials. − Because of the 4f–4f spin-forbidden transition of lanthanide ions, the fluorescence of Ln-MOFs ascribes to the energy transfer from organic linkers to lanthanide ions through the “antenna effect”. Thus, Ln-MOFs actually present multiluminescent responsive sites based on lanthanide ions and organic linkers, which enriches the detection range of analytes including metal ions, anions, explosives, and antibiotics. − Meanwhile, the tunability of MOFs allows the selection of organic linkers with special functional groups or precise control of the pore size to enhance the interaction of targeted analytes, hence improving the detection selectivity and specificity. − Importantly, for the similarity of lanthanide ions, it is feasible to form homogeneous mixed-lanthanide Ln-MOFs, especially Tb/Eu-MOFs.…”