A Fluorescent Cage for Supramolecular Sensing of 3-Nitrotyrosine in Human Blood Serum

Zinc(II) organic framework based bifunctional biomarker sensor for efficient detection of urinary 5-Hydroxyindoleacetic acid and serum 3-Nitrotyrosine

Monitoring biomarker levels in body fluids is of great importance in clinical diagnosis. Herein, a robust 3D ZnMOF, {[Zn2(BTPB)0.5(bib)1.5(μ2-OH)]·2H2O}n, was fabricated based on the ligands of 1,4-bis(2,4,6-tricarboxylpyrid-5-yl)benzene (H6BTPB) and 1,4-bis(imidazol-1-yl)benzene (bib). On the basis of its stable architecture and intrinsic luminescence, ZnMOF demonstrated remarkable potential as a bifunctional luminescent sensor for selective and sensitive detecting the biomarkers of 3-nitrotyrosine (3-NT) and 5-hydroxyindoleacetic acid (5-HIAA) in water and body fluids by employing distinct "turn-off" and "turn-on" responses. Additionally, the inherent sensing mechanism was further assessed from the viewpoints of spectral overlap and photo-induced electron transfer. This work manifested MOFs-based luminescent sensors are developing into an effective method for detecting biomarkers in body fluids with perfect practicality and compatibility.

The Designs and Applications of Tetraphenylethylene Macrocycles and Cages

Macrocycles and cages are very attractive for the development of functional materials due to their unique inner cavities. Building blocks with interesting functions and synthetic conveniences are especially attractive. Tetraphenylethylene (TPE) is such an entity with C2 symmetry and tetrakis-functional groups easily modifiable. As a typical aggregation-induced emission (AIE) active compound, TPE perfectly unites the functions of fluorescence and structural building blocks together. The unique marriage of the two roles into one component makes TPE an ideal platform for the development of functional molecular systems including macrocycles and cages. The TPE macrocycles and cages are not merely a simple combination of those two but also generate added values unseen in either component alone. The fluorescence properties of TPE in macrocycles/cages are greatly improved or modulated, which makes them more suitable for various applications compared to their linear counterparts. In this review, the chemistry and design principles of TPE macrocycles/cages are surveyed first. The unique properties of those compounds are also discussed to provide general guidance for their functionalization. A brief discussion of their applications focusing on the utilization of their unique fluorescence is also presented. In the last, outlooks and future perspectives of TPE macrocycles/cages are provided for further developments.

A Ni(II)MOF-based hypersensitive dual-function luminescent sensor towards the 3-nitrotyrosine biomarker and 6-propyl-2-thiouracil antithyroid drug in urine

Trace detection of bioactive small molecules (BSMs) in body fluids is of great importance for disease diagnosis, drug discovery, and health monitoring. Based on the chiral ligand of 4,4'-(1,2-dihydroxyethane-1,2-diyl)dibenzoic acid (H2L), an achiral 3D porous Ni(II)-MOF, with a trinuclear cluster based (3,9)-c {42·6}3{46·621·89}-xmz net, was constructed under solvothermal conditions. Benefiting from its robust framework and excellent luminescent performance, NiMOF was endowed with remarkable capabilities in efficiently, rapidly, and sensitively detecting the 3-nitrotyrosine (3-NT) biomarker and 6-propyl-2-thiouracil (6-PTU) thyroid drug based on the spectral overlap and photo-induced electron transfer (PET) caused luminescence quenching response. Notably, NiMOF exhibited exceptional performance in quantifying 3-NT and 6-PTU in urine samples, yielding highly satisfactory results. Additionally, an intelligent detection system was crafted to enhance the reliability and practicability of 3-NT/6-PTU detection in urine, based on tandem combinational logic gates. This work not only heralds a promising trajectory in the development of MOF-based luminescent sensors, but also paves the way for the intelligent monitoring of BSMs in real bodily fluids.

Fluorinated 1,7-DO2A-Based Iron(II) Complexes as Sensitive 19F MRI Molecular Probes for Visualizing Renal Dysfunction in Living Mice

Kidney diseases have become an important global health concern due to their high incidence, inefficient diagnosis, and poor prognosis. Devising direct methods, especially imaging means, to assess renal function is the key for better understanding the mechanisms of various kidney diseases and subsequent development of effective treatment. Herein, we developed a fluorinated ferrous chelate-based sensitive probe, 1,7-DO2A-Fe(II)-F18 (Probe 1), for 19F magnetic resonance imaging (MRI). This highly fluorinated probe (containing 18 chemically equivalent 19F atoms with a fluorine content at 35 wt %) achieves a 15-time enhancement in signal intensity compared with the fluorine-containing ligand alone due to the appropriately regulated 19F relaxation times by the ferrous ion, which significantly increases imaging sensitivity and reduces acquisition time. Owing to its high aqueous solubility, biostability, and biocompatibility, this probe could be rapidly cleared by kidneys, which provides a means for monitoring renal dysfunction via 19F MRI. With this probe, we accomplish in vivo imaging of the impaired renal dysfunction caused by various kidney diseases including acute kidney injury, unilateral ureteral obstruction, and renal fibrosis at different stages. Our study illustrates the promising potential of Probe 1 for in vivo real-time visualization of kidney dysfunction, which is beneficial for the study, diagnosis, and even stratification of different kidney diseases. Furthermore, the design strategy of our probe is inspiring for the development of more high-performance 19F MRI probes for monitoring various biological processes.

Reticular Modulation of Piezofluorochromic Behaviors in Organic Molecular Cages by Replacing Non-Luminous Components

Organic piezochromic materials that manifest pressure-stimuli-responses are important in various fields such as data storage and anticounterfeiting. The manipulation of piezofluorochromic behaviors for these materials is promising but remains a great challenge. Herein, a non-luminous components regulated strategy is developed and organic molecular cages (OMCs), a burgeoning class of crystalline organic materials with structural dynamics, are first explored for the design of piezofluorochromic materials with tunable luminescence. A series of OMCs based on aggregation-induced emission (AIE) chromophores, termed Cage 1-3, are synthesized and their piezofluorochromic behaviors are investigated by diamond anvil cell technique. Due to the sufficient voids between its flexible chromophores offered by the OMC structure, Cage 1 exhibits thermofluorochromic and piezofluorochromic properties. Moreover, the piezofluorochromic performance of this OMC could be further promoted by replacing its non-luminous components with improved flexibilities, and a remarkable luminescence peak shift by 150 nm together with a response sensitivity of 13.8 nm GPa-1 was achieved upon hydrostatic compression. The cage structure plays a vital role in facilitating efficient and reversible piezofluorochromic behaviors. This study has shed light on the rational design and exploitation of OMCs as an exceptional platform to accomplish customizable piezofluorochromic behaviors and enlarge their potential applications in pressure-based luminescence.

MXene nanosheet-derived N, S-codoped graphene quantum dots for ultrasensitive and selective detection of 3-nitro-l-tyrosine in human serum

3-Nitro-l-tyrosine (3NT) is an oxidative stress metabolite associated with neurodegenerative diseases such as Parkinson's disease and rheumatoid arthritis. In this study, the N, S-co-doped graphene quantum dots (NSGQDs) derived from nitrogen-doped Ti3C2Tx MXene nanosheet via the hydrothermal method in the presence of mercaptosuccinic acid was synthesized as an optical sensing probe to detect 3NT in human serum. Tetramethyl ammonium hydroxide, the nitrogen source and delamination agent, was used to prepare nitrogen-doped MXene nanosheets via one step at room temperature. The as-prepared NSGQDs are uniform with an average size of 1.2 ± 0.6 nm, and can be stable in aqueous solution for at least 90 d to serve as the fluorescence probe. The N atoms in N-MXene reduce the restacking and aggregation of MXene nanosheets, while the sulfur dopant in NSGQDs increases the quantum yield from 6.2 to 12.1 % as well as enhances the selectivity of 3NT over the other 12 interferences via coordination interaction with nitro group in 3NT. A linear range of 0.02-150 μM in PBS and 0.05-200 μM in human serum with a recovery of 97-108 % for 3NT detection is observed. Moreover, the limit of detection can be lowered to 4.2 and 7 nM in PBS and 1 × diluted human serum, respectively. Results obtained clearly indicate the potential application of the N-Ti3C2Tx derived NSGQD for effective detection of 3NT, which can open a window for the synthesis of doped GQDs via 2D MXene materials for ultrasensitive and selective detection of other biometabolites and biomarkers of neurodegenerative diseases in biological fluids.

Cucurbit[8]uril-Based Supramolecular Probe for the Detection of 3-Nitrotyrosine in Human Serum and Plasma

The biomarker 3-nitrotyrosine (3-NT) is widely recognized as an indicator of renal oxidative stress injury, making its detection crucial for the early identification of renal insufficiency. This study presents the design and synthesis of a tetraphenylstyrene imidazole derivative (TIPE-MI), which is utilized to create a supramolecular probe in conjunction with cucurbit[8]uril (Q[8]) through host-guest interactions. The resulting supramolecular self-assembly exhibits excellent optical properties and has been employed for the specific detection of 3-NT through fluorescence quenching. The introduction of 3-NT resulted in a decreased fluorescence intensity of the yellow fluorescent probe, which gradually transitioned from bright yellow to light yellow and then became colorless as the 3-NT concentration was increased. A portable detection platform was devised to augment the efficiency of detection. In order to facilitate biological applications, we have substantiated the probe's exceptional precision in detecting 3-NT in biological samples, encompassing human serum and plasma. The probe also exhibited negligible cytotoxicity. The accumulation of the probe in renal cells elicited a fluorescence signal, thereby indicating the prospective viability of this system for visual detection with renal cytocompatibility.

Dynamic covalent synthesis

Dynamic covalent synthesis aims to precisely control the assembly of simple building blocks linked by reversible covalent bonds to generate a single, structurally complex, product. In recent years, considerable progress in the programmability of dynamic covalent systems has enabled easy access to a broad range of assemblies, including macrocycles, shape-persistent cages, unconventional foldamers and mechanically-interlocked species (catenanes, knots, etc.). The reversibility of the covalent linkages can be either switched off to yield stable, isolable products or activated by specific physico-chemical stimuli, allowing the assemblies to adapt and respond to environmental changes in a controlled manner. This activatable dynamic property makes dynamic covalent assemblies particularly attractive for the design of complex matter, smart chemical systems, out-of-equilibrium systems, and molecular devices.

Near-infrared Fluorescent Probes with Long-acting Cyclic Monitoring and Effectively Eliminating Peroxynitrite

Two through-bond energy transfer fluorescent probes with a dihydroxyl naphthyl-pyrenyl conjugated system were synthesized for long-acting cyclic monitoring and eliminating peroxynitrite (ONOO- ). The probes exhibit large Stokes shifts (230 or 280 nm) and the fluorescence at 620 or 652 nm rapidly change in response to continuously variable concentrations of ONOO- under physiological conditions. The probes show good reversibility and can rapidly monitor the concentration changes of ONOO- in real time. In addition, with the additions of the probes, the decomposition of ONOO- is greatly accelerated. Therefore, the probes can effectively eliminate the excess ONOO- as well as sensing it. The biological studies showed that the probes can effectively and reversibly eliminate both exogenous and endogenous ONOO- in-situ as well as sensing its changes in cells, which can help to maintain the normal physiological concentration of ONOO- in organisms. This is the first system that a probe achieves multifunction including real-time detection, long-acting cyclic monitoring and in-situ elimination, thereby maintaining a normal physiological balance for ONOO- .

Emissive Click Cages

This study reports the synthesis of cofacial organic cage molecules containing aggregation-induced emissive (AIE) luminogens (AIEgens) through four-fold Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) "click" reactions. The shorter AIEgen, tetraphenylethylene (TPE), afforded two orientational isomers (TPE-CC-1A and TPE-CC-1B). The longer AIEgen, tetrabiphenylethylene (TBPE), afforded a single isomer (TBPE-CC-2). The click reaction employed is irreversible, yet it yielded remarkable four-fold click products above 40 %. The phenyl rings around the ethylene core generate propeller-shaped chirality owing to their orientation, which influences the chirality of the resulting cages. The shorter cages are a mixture of PP/MM isomers, while the longer ones are a mixture of PM/MP isomers, as evidenced by their x-ray structures. The newly synthesized cage molecules are emissive even in dilute solutions (THF) and exhibit enhanced AIE upon the addition of water. The aggregated cage molecules in aqueous solution exhibit turn-off emission sensing of nitroaromatic explosives, with selectivity to picric acid in the 25-38 nanomolar detection range.

Three-in-one covalent organic framework nanozyme: Self-reporting, self-correcting and light-responsive for fluorescence sensing 3-nitrotyrosine

Most current redox-type nanozyme-based colorimetric sensing platforms are susceptible to interference from the reductant when using chromogenic probe, and the unstable H2O2 used in the peroxidase-like nanozyme-based systems is prone to difficulty in sensing signal reproducibility, while peroxidase-like nanozyme with oxidase-mimicking activity is easy to bring background interference by O2. Since the strong structural designability of covalent organic frameworks (COFs) endows them great application value in the sensing fields, therefore, we envision the construction a COF oxidase-like nanozyme-based controllable sensing system that integrates self-reporting, self-correcting and light-responsive functions to avoid these affects. Herein, 3-nitrotyrosine (3-NT) biomarker was selected as model analyte. 1,3,5-triformylphloroglucinol (Tp) and 3,6-diaminoacridine (DA) were acted as building monomers of the multifunctional COF nanozyme (termed as TpDA). Owing to the excellent light-responsive oxidase-mimicking property of TpDA, 3-NT can be efficiently oxidized, the inner filter effect (IFE) between TpDA and the 3-NT oxidation product greatly quenches the intrinsic fluorescence of TpDA, making it a controllable self-reporting system for fluorescence turn-off sensing 3-NT. Additionally, the excessive reactive oxygen species (ROS) that generated continuously during photocatalysis can resist the interference of endogenous reductants. This study not only provides new insights to avoid the interference of H2O2, background and reductants from conventional redox-type nanozyme-based colorimetric systems but also opens avenues to rational construct versatile COF nanozyme-based sensor.

Construction of Covalent Organic Cages with Aggregation-Induced Emission Characteristics from Metallacages for Mimicking Light-Harvesting Antenna

A series of covalent organic cages built from fluorophores capable of aggregation-induced emission (AIE) were elegantly prepared through the reduction of preorganized M2 (LA )3 (LB )2 -type metallacages, simultaneously taking advantage of the synthetic accessibility and well-defined shapes and sizes of metallacages, the good chemical stability of the covalent cages as well as the bright emission of AIE fluorophores. Moreover, the covalent cages could be further post-synthetically modified into an amide-functionalized cage with a higher quantum yield. Furthermore, these presented covalent cages proved to be good energy donors and were used to construct light-harvesting systems employing Nile Red as an energy acceptor. These light-harvesting systems displayed efficient energy transfer and relatively high antenna effect, which enabled their use as efficient photocatalysts for a dehalogenation reaction. This research provides a new avenue for the development of luminescent covalent cages for light-harvesting and photocatalysis.