Novel Lanthanide-Based Metal-Organic Framework Isomer as a Double Ratiometric Fluorescent Probe for Vanillymandelic Acid

Antenna effect-modulated luminescent lanthanide complexes for biological sensing

With the discovery and further exploitation of the antenna effect, the optical properties of luminescent lanthanide complexes (LLCs) have been greatly improved. Antenna effect-modulated LLCs exhibit long luminescence lifetimes, large Stokes shifts, narrow emission spectra, pure chromaticity, and high photostability. Meanwhile, LLCs have garnered considerable attention in recent years and are widely used as biosensors in the fields of food safety, environmental monitoring, clinical diagnosis, and drug analysis. In this review, we first systematically review the design of antenna effect-modulated LLC sensors, including the construction principle of antenna effect in LLCs and the selection of antenna ligands. Secondly, the classification of antenna ligands was discussed in detail. Thirdly, biological sensing applications of antenna effect-modulated LLCs in the past three years are described in terms of the role of LLCs in fluorescence sensors and electrochemiluminescence sensors. Finally, we also discussed the challenges and emerging opportunities of antenna effect-modulated LLCs in future sensing applications.

Regulating the Energy Level of a Ratiometric Luminescent Europium(III) Metal-Organic Framework Sensor with Smartphone Assistance for Real-Time and Visual Detection of Carcinoid Biomarker

Regulating the energy level of a lanthanide (III) metal-organic framework (Ln-MOF) via an "antenna effect" is an effective strategy for achieving the ratiometric luminescent dynamics carcinoid biomarker sensing application. Herein, we present a ratiometric luminescent europium-based MOF material {[Eu(BPDC)(μ3-OH)(H2O)2]·2.5H2O}n (Eu-MOF, H2BPDC = 2,2'-bipyridine-4,4'-dicarboxylic acid and DMF = N,N-dimethylformamide), incorporating tetranuclear cubane-like [Eu4(μ3-OH)4(COO)4]4- cluster cores, for carcinoid biomarker 5-hydroxyindole-3-acetic acid (5-HIAA) detection through the influence of Eu3+ ions sensitized by H2BPDC ligands as well as 5-HIAA. Luminescence titration experiments indicate Eu-MOF can demonstrate simultaneous luminescence emission signals of Eu3+ cations and 5-HIAA, resulting in on-off ratiometric luminescent dynamics 5-HIAA detection in response to 5-HIAA concentrations and demonstrating superior luminescence stability and excellent luminescence emission performance such as low detection limit (LOD = 37.16 nM), high selectivity (Ksv = 2.39 × 104 M-1), fast response (≤1 min), and attractive recyclability (≥five times). Derived from the contribution of the competitive absorption and coordination interactions between Eu3+ cations of Eu-MOF and 5-HIAA, Eu-MOF exhibits a visually observable color change from red to purple by the naked eye illuminated by ultraviolet light, confirmed by the fabrication of portable luminescent hydrogels. More importantly, smartphone assistance based on RGB chromaticity analysis has been developed for the intelligent detection of 5-HIAA, and Eu-MOF@PVA and Eu-MOF@PU films have been proposed for real-time and visual detection of 5-HIAA, thereby enhancing the practical applicability of Eu-MOF in the quantitative trace detection of 5-HIAA.

A Stable Zn(II) Metal-Organic Framework as Turn-On and Blue-Shift Fluorescence Sensor for Amino Acids and Dipicolinic Acid in Living Cells or Using Aerosol Jet Printing

Amino acids and dipicolinic acid (DPA) are important biomarkers for identifying human health. Establishing rapid, accurate, sensitive, and simple assays is essential for disease prevention and early diagnosis. In this work, a novel Zn(II) metal-organic framework (MOF) with the formula {[Zn5(μ3-OH)2(BTDI)2(dpp)2]·dpp·4H2O·2DMF}n (JXUST-53, where JXUST denotes Jiangxi University of Science and Technology, H4BTDI = 5,5'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diisophthalic acid; dpp = 1,3-di(4-pyridyl)propane) was successfully synthesized via a mixed-ligands strategy. JXUST-53 exhibits a three-dimensional (4,10)-connected deh1 topological structure, which remains stable after soaking in aqueous solutions with different pH values (1-12) and organic solvents for at least 24 h, showing high chemical and pH stability. As a potential fluorescence sensor, JXUST-53 can specifically recognize l-threonine (l-Thr), l-histidine (l-His), and DPA in EtOH solutions through fluorescence enhancement and a blue-shift effect. It is worth noting that JXUST-53 is the first MOF-based fluorescence sensor capable of recognizing l-Thr. In addition, the university logo of JXUST with JXUST-53 deposited on it was printed by aerosol jet printing technology, enabling a portable and convenient method for monitoring DPA. More importantly, JXUST-53 has good biocompatibility and low cytotoxicity to sense l-Thr, l-His, and DPA in living cells.

Rapid and sensitive detection of vanillylmandelic acid based on a luminescent fourteen-metal Tb(III) planar nanocluster

A 14-metal Tb(III) nanocluster with four CO32- anions as templates was constructed for the quantitative and qualitative detection of vanillylmandelic acid (VMA) with high sensitivity and selectivity. The luminescence response time to VMA is less than ten seconds, and the limit of detection is as low as 0.32 nM in CH3CN.

Steerable Structural Evolvement and Adsorption Behavior of Metastable Polyoxovanadate-Based Metal-Organic Polyhedra

Promoting the advancement of the structure and function of metastable substances is challenging but worthwhile. In particular, how to harness the entangled state and evolution path of labile porous structures has been at the forefront of research in molecular self-assembly. In this work, the metastable structures of polyoxovanadate-based metal-organic polyhedra (VMOPs) can be manually regulated, including separation of the interlocked aggregate by a ligand-widening approach as well as transformation from a tetrahedral to capsule-like scaffold via a vertice-remodeling strategy. In these processes, intra- and intermolecular π···π and C-H···π interactions have been recognized as the primary driving forces. Besides being responsible for commanding the structural evolvement of VMOPs, such weak interactions were able to program their spatial arrangements and hence the adsorption performances for dye and iodine. The successful use of such a weak force-dominated design concept beacons a feasible route for customization of the function-oriented metastable structures. Separation and transformation of the interlocked metastable VMOPs have been achieved via the respective ligand-widening approach and vertice-remodeling strategy. Not only their structures but also adsorption features could be well regulated by such a weak force-dominated design concept.

Etched-suppressed gold nanorods providing highly distinctive plasmonic patterns: Towards multiplex analysis of neuroblastoma biomarkers

BACKGROUND

On-site monitoring of vanillylmandelic acid (VMA), homovanillic acid (HVA), and dopamine (DA) as key diagnostic biomarkers for a wide range of neurological disorders holds utmost significance in clinical settings. Numerous colorimetric sensors with mechanistic approaches based on aggregation or silver metallization have been introduced for this purpose. However, these mechanisms have drawbacks, such as sensitivity to environmental factors and probe toxicity. Therefore, there is a great demand for a robust yet non-toxic colorimetric sensor that employs a novel route to monitor these biomarkers effectively.

RESULTS

Here, we present a single-component multi-colorimetric probe based on the controllable etching suppression of gold nanorods (AuNRs) upon exposure to the mild etchant N-bromosuccinimide (NBS), designed to accurately detect and discriminate VMA, HVA, DA, and their corresponding mixtures, i.e.

, VMA

HVA, VMA:DA, HVA:DA, and VMA:HVA:DA. To enhance the sensitivity and automation capabilities of the designed multi-colorimetric sensor, two machine learning techniques were employed: linear discriminant analysis (LDA) for the qualitative classification and partial least-squares regression (PLSR) for the quantitative analysis of pure biomarkers and their mixtures. The outcomes revealed a high correlation between measured and predicted values, covering a linear range of 0.8-25, 1.2-25, and 2.7-100 μmol L-1, with remarkably low detection limits of 0.260, 0.397, and 0.913 μmol L-1 for VMA, HVA, and DA, respectively. Lastly, the performance of the probe was validated by successfully detecting the neuroblastoma biomarker VMA:HVA in human urine.

SIGNIFICANCE

Our designed multi-colorimetric probe introduces a rapid, cost-effective, user-friendly, non-toxic, and non-invasive approach to detecting and discriminating not only the pure biomarkers but also their corresponding binary and ternary mixtures. The distinctive response profiles produced by the probe in the presence of different mixture ratios can indicate various disease states in patients, which is highly crucial in clinical diagnostics.

Multifunctional Luminescent 3D Ln-MOFs with High Sensitivity for Trace Detection of Micronutrients

The synthesis of two versatile fluorescent metal-organic frameworks (MOFs), [Eu(4-NCP)(1,4-bdc)]n·0.5H2O (1) and [Eu(4-NCP)(4,4'-bpdc)]n·0.75H2O (2) (HNCP = 2-(4-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline, 1,4-H2bdc = benzene-1,4-dicarboxylic acid, 4,4'-H2bpdc = 4,4'-biphenyldicarboxylic acid), was carried out using a hydrothermal method. These MOFs were characterized through various advanced technologies to determine their structural information. The results indicate that both MOFs exhibited 3D network structures with specific topologies. Furthermore, these MOFs demonstrated exceptional thermal stabilities and adsorption capabilities. Additionally, complex 2 was utilized for studying the fluorescence sensing properties of various micronutrients including metal ions, nitro aromatic compounds, and biological small molecules. Notably, complex 2 showed promising potential as a multifunctional sensor for selectively detecting Fe3+, nitrobenzene, and ascorbic acid in aqueous solutions through fluorescence quenching with low limits of detection (LODs ∼ 10-7 M) and high quenching constants (Ksv ∼ 103 M-1). Moreover, the detection mechanism of complex 2 was further investigated by using experimental methods and DFT calculations.