Designing an “Off–On” Fluorescence Sensor Based on Cluster-Based Ca^II-Metal–Organic Frameworks for Detection of l-Cysteine in Biological Fluids

Abstract

Recently, luminescent metal−organic framework (MOF) materials have attracted considerable attention in fluorescence sensing. In this essay, we prepared a new clusterbased Ca II -MOFs {[Ca 1.5 (μ 8 -HL 1 )(DMF) 2 ]•DMF} n (1) with good water dispersibility, excellent photoluminescence properties (FL quantum yield of 20.37%) and great fluorescence stability. Further, it was employed to design as an "off−on" fluorescence sensor for sensitive detection of L-cysteine. This proposed strategy was that fluorescence of Ca II -MOFs 1 was quenched for providing a low fluorescence background by the introduction of Pb 2+ forming the Ca II -MOFs 1/Pb 2+ hybrid system. The quenching effect could be ascribed to the static quenching mechanism because of the formation of ground-state complexes and coordination interactions between the free carboxyl of H 4 L 1 ligands of Ca II -MOFs 1 and Pb 2+ . Then, with the addition of L-cysteine into the Ca II -MOFs 1/Pb 2+ hybrid system, the fluorescence signal was immediately restored. This result was because the Pb 2+ was gradually released from the hybrid system by chelation interactions between the −SH groups of L-cysteine and Pb 2+ . This method received a relative wide linear range varying from 0.05 to 40 μM and a low detection limit of 15 nM for detection of L-cysteine. This proposed strategy was also successfully applied to detect L-cysteine in human serum samples with satisfactory recoveries from 95.9 to 101.5%.

Highly Sensitive and Selective Luminescence Sensor Based on Two-Fold Interpenetrated MOFs for Detecting Glutamate in Serum

“…As previously mentioned, the relationship between I 0 / I and the concentration of glutamate can be well fitted into the S–V equation at lower concentrations, suggesting the contribution of dynamic quenching processes in luminescence quenching . On the contrary, it is known to us all that when static quenching happens, luminescent substances will interact with quenching agents, forming ground-state complexes and influencing the absorption spectrum of luminescent substances . Therefore, we tested the liquid UV–vis absorption spectra of 1 in deionized water and in glutamate solution (10 –4 mol/L).…”

“…49 On the contrary, it is known to us all that when static quenching happens, luminescent substances will interact with quenching agents, forming ground-state complexes and influencing the absorption spectrum of luminescent substances. 52 Therefore, we tested the liquid UV−vis absorption spectra of 1 in deionized water and in glutamate solution (10 −4 mol/L). It can be seen from Figure S15 that the broad peak displays a clear decrease in the absorbance and shape change after the addition of the glutamate solution.…”

Morphology Effect of One-Dimensional MnO2 Nanostructures on Heteroatom-Doped Carbon Dot-Based Biosensors for Selective Detection of Glutathione

“…16,45 Generally, the ground-state complex formation leads to the occurrence of static quenching with the variation of UV−visible absorption spectra of the fluorescent material and, on the other hand, no change in the decay time due to the presence of an analyte. 46,47 However, the change in the decay time of the fluorescent material with the addition of a quencher results in dynamic quenching. Further, PET is a redox process in which fluorescence quenching occurs when a molecule can accept or donate the electrons of a fluorescent material present in the excited state.…”

Enhancing K2S2O8 electrochemiluminescence based on silver nanoparticles and zinc metal–organic framework composite (AgNPs@ZnMOF) for the determination of l-cysteine

“…22 Therefore, it will be an ideal diagnostic indicator for detecting serum or urine l -Cys in the patients at risk for cystine stone formation or with early renal injury of Diabetes Mellitus. 23,24 So far, a number of methodologies for detecting l -Cys have been developed, including fluorescence methods, 25 colorimetry, 26 electrochemical detection, 27 capillary electrophoresis 28 and high performance liquid chromatography. 29 ECL assays for determining l -Cys were also reported previously; 30,31 the determination of l -Cys by ECL methods has higher sensitivity compared to other methods.…”