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BACKGROUND: Dandelion contains hundreds of active compounds capable of inhibiting urease activity, but the individual compounds have not yet been fully identified, and their effects and underlying mechanisms are not clear. The present study aimed to screen the urease inhibition active compounds of dandelion by urease inhibitory activity evaluation HPLC‐tandem mass spectrometry analysis, their mechanism of urease inhibition by polyphenols was explored using enzyme kinetic studies via Lineweaver‐Burk plots. Other investigations included isothermal titration calorimetry and surface plasmon resonance sensing, fluorescence quenching experiments, and single ligand molecular docking and two‐ligand simultaneous docking techniques. RESULTS: The results indicated that the ethyl acetate fraction of dandelion flower exhibited the greatest inhibition (lowest IC50 0.184 ± 0.007 mg mL−1). Chlorogenic acid, caffeic acid and luteolin could be effective urease inhibitors that acted in a non‐competitive inhibition manner. Individually, chlorogenic acid could not only fast bind to urease, but also dissociate rapidly, whereas luteolin might interact with urease with the weakest affinity. The chlorogenic acid‐caffeic acid combination exhibited an additive effect in urease inhibition. However, the chlorogenic acid‐luteolin and caffeic acid‐luteolin combinations exhibited antagonistic effects, with the caffeic acid‐luteolin combination showing greater antagonism. CONCLUSION: The present study reveals that chlorogenic acid, caffeic acid and luteolin are major bioactive compounds for urease inhibition, indicating the molecular mechanisms. The antagonistic effects were observed between luteolin and chlorogenic acid/caffeic acid, and the interactions of the catalytic site and flap may account for the antagonistic effects. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Tetracyclines (TCs) rank second globally in the use of animal infection therapy and animal husbandry as growth promoters among all antibiotics. However, large amounts of TCs residue in food products and more than 75% of TCs are excreted into the environment, causing adverse effects on the ecological system and human health. It has been challenging to simultaneously realize low-cost, rapid, and highly selective detection of TCs. Here, inspired by the fluorogenic reactions between resorcinol and catecholamines, we find the fluorescence quenching ability of tetracycline (TC) and firstly propose a fluorescent "turn-off" detection of TC using dopamine and 4-fluororesorcinol. The optimal reaction condition for the fluorescent assay is investigated and the optimized probe showed a good limit of detection (LOD of 1.7 µM) and a wide linear range (10 µM to 350 µM). Moreover, this fluorescent assay proved to be an effective tool for detecting TC in river, Sprite, and beer samples, which represent the aquatic environments and food and may contain tetracyclines residues. Finally, the high selectivity of the method for TC has been confirmed by eliminating the interference from common substances. The proposed strategy provides a high-efficiency and selective solution for the detection of TCs in environment and food and the application fields of this fluorescent assay could be further expanded in the future. [ABSTRACT FROM AUTHOR]

The human palate can discern multiple tastes; however, it predominantly perceives five fundamental flavors: sweetness, saltiness, sourness, bitterness, and umami. Sweetness is primarily mediated through the sweet taste receptor, a membrane-bound heterodimeric structure comprising T1R2-T1R3. However, unraveling the structural and mechanistic intricacies of the sweet taste receptor has proven challenging. This study aimed to address this knowledge gap by expressing an extracellular N-terminal domain encompassing the cysteine-rich domain of human hT1R3 (hT1R3-TMD) in Escherichia coli. The expressed protein was obtained as inclusion bodies, purified by metal affinity chromatography, and refolded using the dilution-refolding method. Through rigorous analysis, we confirmed the successful refolding of hT1R3-TMD and elucidated its structural characteristics using circular dichroism spectroscopy. Notably, the refolded protein was found to exist as either a monomer or a dimer, depending on its concentration. A tryptophan fluorescence quenching assay revealed that the dissociation constants for sucrose, sucralose, and brazzein were >9500 μM, 2380 μM and 14.3 μM, respectively. Our findings highlight the utility of this E. coli expression system for producing functional hT1R3-TMD for investigations and demonstrate the efficacy of the tryptophan fluorescence quenching assay in revealing complex interactions between sweet taste receptors and various sweeteners. [ABSTRACT FROM AUTHOR]

AbstractPurposeMaterials and MethodsResults and ConclusionsThe study of mechanisms of plant responses to extreme conditions, particularly, microgravity and ionizing radiation, is crucial for space exploration. Modern space biology of plants focuses on increasing plant tolerance to harsh conditions of space environment. Given the limited access to the International Space Station, we designed and assembled the 3D clinostat for mimicking microgravity, which, in combination with proton irradiation, allows simulating space conditions. As a case study for testing the device, we studied the effect of clinostating on Arabidopsis thaliana accession originating from the Chernobyl exclusion zone.Using the combined clinostating and proton irradiation, we simulated the conditions of long-term space flight for Arabidopsis thaliana plants of the Chernobyl accession – progeny of chronically irradiated plants, grown from field-collected (Masa-0) and laboratory-cultivated (Masa-0-1) seeds, and for wild-type Col-8. The clinostating and irradiation of plants were also carried out separately. Plant responses were studied as photosynthetic and phenotypic endpoints of seedlings.Parameters of chlorophyll fluorescence estimated immediately after exposure showed that Masa-0-1 plants were resistant to the simulated space conditions, while Masa-0 demonstrated modulation of non-photochemical fluorescence quenching. Proton irradiation generally inhibited photosynthesis of Masa-0, Masa-0-1, and Col-8 seedlings. The combined effect of irradiation and clinostating modulated the photosynthetic activity of Col-8 seedlings. The leaf area of seedlings did not change after exposure to simulated conditions. The 3D clinostat model and software are published along with this article for researchers interested in the field of space biology. [ABSTRACT FROM AUTHOR]

Purpose: We explore the use of intravenously delivered fluorescent perfluorocarbon (PFC) nanoemulsion tracers and multi-spectral cryo-fluorescence tomography (CFT) for whole-body tracer imaging in murine inflammation models. CFT is an emerging technique that provides high-resolution, three-dimensional mapping of probe localization in intact animals and tissue samples, enabling unbiased validation of probe biodistribution and minimizes reliance on laborious histological methods employing discrete tissue panels, where disseminated populations of PFC-labeled cells may be overlooked. This methodology can be used to streamline the development of new generations of non-invasive, cellular-molecular imaging probes for in vivo imaging. Procedures: Mixtures of nanoemulsions with different fluorescent emission wavelengths were administered intravenously to naïve mice and models of acute inflammation, colitis, and solid tumor. Mice were euthanized 24 h post-injection, frozen en bloc, and imaged at high resolution (~ 50 µm voxels) using CFT at multiple wavelengths. Results: PFC nanoemulsions were visualized using CFT within tissues of the reticuloendothelial system and inflammatory lesions, consistent with immune cell (macrophage) labeling, as previously reported in in vivo magnetic resonance and nuclear imaging studies. The CFT signals show pronounced differences among fluorescence wavelengths and tissues, presumably due to autofluorescence, differential fluorescence quenching, and scattering of incident and emitted light. Conclusions: CFT is an effective and complementary methodology to in vivo imaging for validating PFC nanoemulsion biodistribution at high spatial localization, bridging the resolution gap between in vivo imaging and histology. [ABSTRACT FROM AUTHOR]

Clusterization‐triggered emissive (CTE) materials have attracted great attention in recent years. The regulation of the emission property of materials with CTE property through supramolecular interactions is an excellent strategy for the construction of smart fluorescent materials. In this work, we have prepared a regulatable supramolecular polymer network with CTE properties through pillararene‐based host−guest interactions. The pillar[5]arene‐grafted poly(methyl methacrylate) (PMMA) showed a classic CTE character. After adding Brooker's merocyanine‐grafted polymer to the solution of the pillar[5]arene‐containing PMMA, the supramolecular polymer network gel formed by the host−guest interactions between pillararene and Brooker's merocyanine guest. This supramolecular network showed brighter fluorescence than the pillar[5]arene‐grafted PMMA in the solid state. In addition, the fluorescence emission of the supramolecular network can be further regulated by pH conditions. After adding an acid, the Brooker's merocyanine‐containing guest polymer was protonated, and the supramolecular network changed to a protonated network through host−guest interactions between protonated Brooker's merocyanine guest and pillararene. Interestingly, the fluorescence was quenched when the supramolecular network turned into the protonated network. After adding a base, the protonated network can convert back to the original network, along with recovery of the fluorescence. Therefore, the regulation of the fluorescence of the supramolecular polymer materials with CTE was successfully realized by pillararene‐based host−guest interactions. Furthermore, this tailorable fluorescent supramolecular polymer network system was applied as an information encryption material. [ABSTRACT FROM AUTHOR]

(1) Background: The non-enzymatic glycation of proteins is a significant contributor to the formation of advanced glycation end products (AGEs) and intermediates that are responsible for diabetic complications. It is imperative to explore effective inhibitors to prevent protein glycation. (2) Methods: This study aimed to investigate the inhibitory potential of various aqueous ethanol extracts of poplar-type propolis on AGEs and oxidative modifications in bovine serum albumin (BSA)-glucose and BSA-methylglyoxal models. (3) Results: The results revealed that these propolis extracts exhibited significant effectiveness in inhibiting the formation of total AGEs, pentosidine, and Nε-carboxymethyllysine (CML). Furthermore, the investigation discovered that these propolis extracts can effectively inhibit oxidative modification, based on measuring the levels of carbonyl and thiol groups and analyzing tryptophan fluorescence quenching. Notably, 75% ethanol extracts of propolis (EEP) exhibited the highest inhibitory activity, surpassing the chemical inhibitor aminoguanidine (AG). (4) Conclusions: The remarkable anti-glycation potency of aqueous ethanol extracts of poplar-type propolis can be attributed to their elevated contents of phenolic compounds, especially abundant flavonoids, which inhibit the formation of AGEs by scavenging free radicals, decreasing the levels of reactive oxygen species (ROS), and capturing reactive carbonyl species (RCS) in the protein glycation process. Our results indicate that poplar-type propolis may be a potential AGE inhibitor and could be used to develop functional foods and nutraceuticals to prevent diabetic complications. [ABSTRACT FROM AUTHOR]

Trypsin enzyme has gained recognition as a potential biomarker in several tumors, such as colorectal, gastric, and pancreatic cancer, highlighting its importance in disease diagnosis. In response to the demand for rapid, cost-effective, and real-time detection methods, we present an innovative strategy utilizing the design and synthesis of NIR-sensitive dye–peptide conjugate (SQ-3 PC) for the sensitive and selective monitoring of trypsin activity by fluorescence ON/OFF sensing. The current research deals with the design and synthesis of three unsymmetrical squaraine dyes SQ-1, SQ-2, and SQ-3 along with a dye–peptide conjugate SQ-3-PC as a trypsin-specific probe followed by their photophysical characterizations. The absorption spectral investigation conducted on both the dye alone and its corresponding dye–peptide conjugates in water, utilizing SQ-3 and SQ-3 PC respectively, reveals enhanced dye aggregation and pronounced fluorescence quenching compared to observations in DMSO solution. The absorption spectral investigation conducted on dye only and corresponding dye–peptide conjugates in water utilizing SQ-3 and SQ-3 PC, respectively, reveals not only the enhanced dye aggregation but also pronounced fluorescence quenching compared to that observed in the DMSO solution. The trypsin-specific probe SQ-3 PC demonstrated a fluorescence quenching efficiency of 61.8% in water attributed to the combined effect of aggregation-induced quenching (AIQ) and fluorescence resonance energy transfer (FRET). FRET was found to be dominant over AIQ. The trypsin-mediated hydrolysis of SQ-3 PC led to a rapid and efficient recovery of quenched fluorescence (5-fold increase in 30 min). Concentration-dependent changes in the fluorescence at the emission maximum of the dyes reveal that SQ-3 PC works as a trypsin enzyme-specific fluorescence biosensor with linearity up to 30 nM along with the limit of detection and limit of quantification of 1.07 nM and 3.25 nM, respectively. [ABSTRACT FROM AUTHOR]

Schiff base complexes play a crucial role in bioinorganic chemistry. A novel curcumin/phenylalanine tridentate Schiff base ligand and its palladium (II) complex were synthesized so that they were stable in aqueous buffer. The structure of the complex was investigated using a variety of methods, including DFT, NBO analysis, FMOs, and MESP. The interaction of the complex with a plasmid (pUC19) and CT-DNA was studied. The anticancer, antibacterial, and antioxidant activities of the complex were examined. The statistical analysis of the MTT assay was compared using the 1-way ANOVA and Tukey test. Results showed that the complexes were stable in aqueous buffer, pH 8. The extrinsic fluorescence emission of the plasmid and CT-DNA was quenched while interacting with the complex. The complex had an IC50 of 72.47 µM against MCF-7 cells. The ANOVA and Tukey analysis of MTT data demonstrated a statistically significant difference between groups (P < 0.0001). The minimum inhibitory concentrations (MIC) of the complex for E. coli and S. aureus were 300 and 200 µg/mL, with 96.3 and 95.2% biofilm growth inhibition at 250 µg/mL, respectively. The sample concentrations contributing to 50% radical inhibition in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) test for curcumin, ligand, and palladium (II) complex were 33.62, 21.27, and 51.26 µM, respectively. The results suggest that the complex interaction with DNA is one of the potential mechanisms for eliminating cancer cells and bacteria in the planktonic and biofilm. On the other hand, while stability in an aqueous buffer at pH 8 increases, the modified curcumin antioxidant effect decreases. [ABSTRACT FROM AUTHOR]

Hydroxamic acids represent a group of weak organic acids, both naturally occurring and synthetically derived, characterized by the general formula RC(= O)N(R'OH). In this study, we investigated the binding behavior of N-m-tolyl-4-chlorophenoxyaceto hydroxamic acid with calf thymus DNA (ct-DNA) and torula yeast RNA (t-RNA) through a combination of techniques including UV–visible spectroscopy, fluorescence emission analysis, viscometry, and computational simulations using AutoDock4 software. Our findings reveal that the mode of binding between the compound and the nucleic acids is consistent with intercalation. Competitive binding experiments demonstrated that the complex competes effectively with ethidium bromide (EB) for binding to ct-DNA/t-RNA, displacing EB from its binding sites. Additionally, the introduction of the compound into the DNA-EB system resulted in a quenching of fluorescence emission peaks. Analysis of absorption spectra indicated a red shift and hypochromic shift when the compound interacted with DNA, further supporting the intercalative binding mode. The calculated binding constant (Kb) value for the compound is 6.62 × 104 M−1 and 5.40 × 103 M−1 indicating a strong interaction with ct-DNA and t-RNA respectively. We determined the Stern–Volmer constants for ct-DNA and t-RNA as 9.96 × 104 M−1 and 8.13 × 105 M−1, respectively. The binding free energy values for ct-DNA/t-RNA were calculated to be − 3.741 × 107 and − 5.425 × 108 kcal/mol, respectively. Viscometric studies corroborated the UV results, showing a continuous increase in relative viscosity of ct-DNA/t-RNA solutions with the addition of the optimal hydroxamic acid concentration. Furthermore, we assessed the antioxidant activity of the compound using DPPH-radical scavenging and β-carotene linoleic acid assays. Gel electrophoresis results demonstrated the compound's remarkable efficacy in preventing DNA damage. Collectively, all experimental evidence supports the conclusion that N-m-tolyl-4-chlorophenoxyaceto hydroxamic acid binds to ct-DNA/t-RNA through an intercalative mechanism, which is consistent with our molecular docking simulations. [ABSTRACT FROM AUTHOR]

Redox imbalance and oxidative stress are increasingly recognized as significant factors in health disorders such as neurodegenerative disorders, premature aging and cancer. However, detecting antioxidant levels that is crucial for managing oxidative stress, can be challenging due to existing assays' limitations, such as insensitivity to thiol-containing antioxidants. This study presents a simple fluorescence-based assay for antioxidant detection employing the enhanced photocatalytic oxidase-like activity of dithiothreitol (DTT)-assisted bovine serum albumin (BSA)-stabilized gold nanoclusters (DTT@BSA-AuNCs). The reported nanozyme exhibits remarkable stability, versatility, and catalytic activity. Under LED irradiation, DTT@BSA-AuNCs generate singlet oxygen, which converts non-fluorescent thiamine to fluorescent thiochrome, utilizing dissolved oxygen for catalysis. Antioxidants inhibit thiochrome formation, leading to fluorescence quenching. This method enables sensitive detection of antioxidants such as ascorbic acid and glutathione with limits of detection of 0.08 µM and 0.32 µM, respectively, under neutral pH, outperforming previous studies. The assay successfully detects antioxidants in human saliva and cancer cell models. The DTT@BSA-AuNCs-based assay offers a cost-effective, sensitive, and straightforward approach for detecting antioxidants in biological samples, facilitating improved monitoring of oxidative stress in various diseases. [ABSTRACT FROM AUTHOR]

Hydrazine hydrate and hydrogen peroxide are both important raw materials for industrial production and have a wide range of applications in several fields. Owing to their damage to the human body and cellular functions by excessive exposure or ingestion, it is essential to develop an efficient and rapid assay for the detection of hydrazine hydrate and hydrogen peroxide. Fluorescence switches have been applied in many fields including for metal ion detection. However, the assembly of Prussian blue (PB) and carbon quantum dots (CDs) has never been reported for the fabrication of a fluorescence switch for the detection of hydrazine and hydrogen peroxide. In this work, a fluorescent switch PB@CD/SiO2 based on PB and CDs was constructed, which could be used as a detection platform for hydrazine hydrate and hydrogen peroxide. The surface of PB was coated with a silica layer, which contained CDs to fabricate PB@CD/SiO2 nanoparticles. The composite demonstrated reversible switching between fluorescence quenching and recovering states through the mutual conversion of PB and Prussian white (PW). The prepared composite was utilized for the detection of N2H4 and H2O2 by fluorescence spectroscopy and UV-vis absorption spectroscopy. It is worth-mentioning that the detection limit for N2H4 is calculated to be 0.15 μM (fluorescence) and the detection limit for H2O2 can reach 0.93 μM (UV). Moreover, both detection methods showed low detection limits, wide detection ranges and a short response time for N2H4 and H2O2. The proposed fluorescence switch system exhibits good performance towards the dual-spectral determination of hydrazine and hydrogen peroxide by fluorescence spectroscopy and UV-vis spectroscopy, which may be beneficial for further application in practical fields. [ABSTRACT FROM AUTHOR]

Hydrazine hydrate and hydrogen peroxide are both important raw materials for industrial production and have a wide range of applications in several fields. Owing to their damage to the human body and cellular functions by excessive exposure or ingestion, it is essential to develop an efficient and rapid assay for the detection of hydrazine hydrate and hydrogen peroxide. Fluorescence switches have been applied in many fields including for metal ion detection. However, the assembly of Prussian blue (PB) and carbon quantum dots (CDs) has never been reported for the fabrication of a fluorescence switch for the detection of hydrazine and hydrogen peroxide. In this work, a fluorescent switch PB@CD/SiO2 based on PB and CDs was constructed, which could be used as a detection platform for hydrazine hydrate and hydrogen peroxide. The surface of PB was coated with a silica layer, which contained CDs to fabricate PB@CD/SiO2 nanoparticles. The composite demonstrated reversible switching between fluorescence quenching and recovering states through the mutual conversion of PB and Prussian white (PW). The prepared composite was utilized for the detection of N2H4 and H2O2 by fluorescence spectroscopy and UV-vis absorption spectroscopy. It is worth-mentioning that the detection limit for N2H4 is calculated to be 0.15 μM (fluorescence) and the detection limit for H2O2 can reach 0.93 μM (UV). Moreover, both detection methods showed low detection limits, wide detection ranges and a short response time for N2H4 and H2O2. The proposed fluorescence switch system exhibits good performance towards the dual-spectral determination of hydrazine and hydrogen peroxide by fluorescence spectroscopy and UV-vis spectroscopy, which may be beneficial for further application in practical fields. [ABSTRACT FROM AUTHOR]

Carbon dots have emerged as highly efficient and versatile fluorescent probes for detecting and quantifying Hg2+. This study reports a method to prepare nitrogen-doped carbon dots (N-CDs) via ligand-to-metal charge transfer fluorescent quenching for Hg2+ detection. Besides the excitation-independent emission feature, the synthesized N-CDs demonstrate a high selectivity of Hg2+ over 23 potentially interfering environmental ions. The structures of 2-hydroxy-N,N-dimethylbenzamide and amide functional groups are identified as the determinants of the relatively high quantum yield (53.33%). N-CDs also exhibit a linear relationship with Hg2+ concentration in the range of 0.007–120 μM, with a limit of detection of 7.1 nM. The produced N-CDs can be employed in a customized microfluidic real-time monitoring platform, demonstrating the robustness in receiving efficient fluorescence signals with a satisfactory limit of detection. The acceptable accuracy and recovery of Hg2+ detection in tap water and river water highlight the potential practical applications of the synthesized N-CDs. Results in this study can facilitate the development of a portable device for early warning of water pollution. [ABSTRACT FROM AUTHOR]

Rapid, sensitive, and accurate detection of Cr2O72− in the environment is of great significance. This article synthesized water‐soluble N and S‐doped carbon quantum dots (N,S‐CQDs) using a simple hydrothermal self‐assembly pathway through hydrogen bonding of melamine and trithiocyanuric acid. N,S‐CQDs show green fluorescence under visible light excitation at 420 nm, with a high fluorescence quantum yield of 33.4%. Under photo‐induced electron transfer, significant fluorescence dynamic quenching occurred in N,S‐CQDs when a solution containing Cr2O72− was added. Based on this specific response, the selective and sensitive probe for Cr2O72− is achieved, with a wide detection concentration of up to 33 µm. The limits of detection can be as low as 0.11 µm. This work provides an easy‐prepared N,S‐CQDs for sensitive detecting of Cr2O72− in the environment. [ABSTRACT FROM AUTHOR]

Real‐time tracking of drug release from nanomedicine in vivo is crucial for optimizing its therapeutic efficacy in clinical settings, particularly in dosage control and determining the optimal therapeutic window. However, most current real‐time tracking systems require a tedious synthesis and purification process. Herein, a supramolecular nano‐tracker (SNT) capable of real‐time tracking of drug release in vivo based on non‐covalent host‐guest interactions is presented. By integrating multiple cavities into a single nanoparticle, SNT achieves co‐loading of drugs and probes while efficiently quenching the photophysical properties of the probe through host‐guest complexation. Moreover, SNT is readily degraded under hypoxic tumor tissues, leading to the simultaneous release of drugs and probes and the fluorescence recovery of probes. With this spatial and temporal consistency in drug loading and fluorescence quenching, as well as drug release and fluorescence recovery, SNT successfully achieves real‐time tracking of drug release in vivo (Pearson r = 0.9166, R2 = 0.8247). Furthermore, the released drugs can synergize effectively with fluorescent probes upon light irradiation, achieving potent chemo‐photodynamic combination therapy in 4T1‐bearing mice with a significantly improved survival rate (33%), providing a potential platform to significantly advance the development of nanomedicine and achieve optimal therapeutic effects in the clinic. [ABSTRACT FROM AUTHOR]

Reported herein is an ultra-sensitive turn-off fluorescence sensor for hydrogen peroxide based on its reaction with bimane 1. This reaction is highly efficient, resulting in a detection limit of 7.9 pM. It also maintains sensor efficacy when adsorbed on paper and enables both solution-state and vapor-phase detection. [ABSTRACT FROM AUTHOR]

Fluorescent foams with interconnected pores are attractive for the detection and quantification of various products. However, many fluorescent probes are suffering from aggregation‐caused fluorescence quenching in their solid/aggregated state, are costly, and/or not straightforward to incorporate in foams, limiting their utility for this application. Herein, non‐isocyanate polyurethane foams, prepared by the simple water‐induced self‐blowing process, present a nonconventional fluorescence behaviour, i.e. they are intrinsically fluorescent with a multicolor emission without requiring ex situ traditional fluorescent probes. These foams demonstrate utility for capturing‐sensing gaseous formaldehyde (an emblematic indoor air pollutant), as well as for detecting and quantifying various metal ions (Fe2+, Cu2+, Fe3+, Hg2+). They are also able to selectively sense tetracycline antibiotic in a ratiometric way with a high sensitivity. By exploiting the unique multicolor photoluminescent foam properties, a smartphone‐compatible device is used for the facile antibiotic quantification. This nonconventional fluorescence behaviour is discussed experimentally and theoretically, and is mainly based on clusteroluminescence originating from multiple hydrogen bonding and hetero‐atomic sub‐luminophores, thus from aggregation‐induced emission luminogens that are naturally present in the foams. This work illustrates that easily accessible non‐conventional fluorescent NIPU foams characterized by a modular emission wavelength have an enormous potential for multiple substrates detection and quantification. [ABSTRACT FROM AUTHOR]

The interaction between linamarin (LIN), a cyanogenic glycoside, and human serum albumin (HSA) was studied by multiple spectroscopic techniques and molecular docking simulation. All measurements were performed under physiological conditions. The obtained results (including the binding constants, effective quenching constant and a number of binding sites) showed that the complex of HSA‐LIN is formed. The values of Stern‐Volmer constants (6.70×103, 5.53×103 and 1.95×103) indicate that fluorescence quenching of HSA was static. Results of site marker experiments showed that the binding site of LIN is mainly located in site I (subdomain IIA) of HSA. The thermodynamic parameters showed that binding process occurs spontaneously through hydrophobic interactions. Molecular docking results are in good agreement with experimental data. Furthermore, computational results revealed LIN binds in the cavity of TRP 214, that is, subdomain IIA (site I) of HSA. This comprehensive study provides a deeper insight into ligand binding in HSA which may be useful in drug design and pharmacology. [ABSTRACT FROM AUTHOR]

Two‐photon excited fluorescence is a process in which the excited fluorophore relaxes and emits fluorescence after two‐photon absorption. Combined with appropriate two‐photon fluorescent probes, two‐photon microscopy enables observation deep inside tissue without damage. Former reports showed that the two‐photon absorption cross sections of donor–acceptor (D–A) dipoles, as well as D‐π‐D and D–A–D quadrupoles can be strengthened by using strong D–A groups. In this study, a novel water‐soluble fluorescent probe with D‐π‐A structure containing pyridine‐2,6‐dicarboxylic acid unit was synthesized. The maximum excitation wavelength and emission wavelength of the probe in aqueous solution were 328 nm and 471 nm, respectively. The fluorescence emitted by the probe can be quenched by various metal cations. The pyridyl N and carboxyl O in the probe formed chelates with Cu2+, which resulted in a fluorescence quenching response, and showed a linear relationship between fluorescent intensity and Cu2+ concentration with wide linear range and low limit of detection. CCK‐8 tests showed the probe had no obvious toxicity to 4T1 cells in the range of 0.4–50 μmol L−1, and the cell survival rate was above 86 %. The probe had a large two‐photon absorption cross section ranging from 680 nm to 820 nm. The two‐photon absorption cross section reached 100 GM at 760 nm of excitation wavelength. By means of microscopic imaging of 4T1 cells stained with the probe, one‐photon fluorescence represented blue emission, while two‐photon fluorescence represented bright green emission. The probe was proved to have good cell permeability, and preferred to target nucleus, showing application potential in two‐photon fluorescence imaging technology. [ABSTRACT FROM AUTHOR]

In this study, a novel fluorescence nanoprobe based on Materials of Institute Lavoisier (MIL-101) metal-organic frameworks embedding into the agarose hydrogel is fabricated using a hydrothermal technique. It uses for sensitive quantification of deferiprone in exhaled breath condensate (EBC) samples. The morphology and characterization of MIL-101/agarose nanocomposite hydrogel is studied by transmission electron microscopy, dynamic light scattering instrument, powder X-ray diffraction analysis, and Fourier transform infrared spectroscopy. The probe shows a reasonable fluorescence intensity quenching in the presence of deferiprone due to the interactions between iron centers in MIL-101 (Fe) and deferiprone, which likely form non-fluorescent complexes. The proposed nanoprobe demonstrates a linear calibration curve from 0.005 to 1.5 µg mL− 1 with a detection limit of 0.003 µg mL− 1. The intra- and inter-day precision of the reported method are 0.3% and 0.4% (n = 5, deferiprone concentration = 1.0 µg mL− 1), respectively. This method demonstrates high sensitivity and specificity towards deferiprone in the EBC samples and also presents a sensing platform with simplicity, convenience, fast implementation, and cost-effective in medical monitoring. [ABSTRACT FROM AUTHOR]

A remarkable and unexpected increase in the photopolymerization efficiency of an acrylic resin by a bisacylphosphine oxide photoinitiator was observed when an optical brightener was present in the medium. High values for the maximal rates of photopolymerization were obtained by RT‐FTIR at 365 nm under a very low irradiance of 1 mW/cm2. Fluorescence studies revealed that the quenching process occurs through singlet‐singlet energy transfer between the first singlet excited state of the optical brightener and the ground state photoinitiator. This mechanism acts as an additional pathway for the excitation of the photoinitiator, thereby increasing the total amount of initiating radicals. Using the Förster resonance energy transfer model, we calculated the relative efficiency of the photosensitization process with respect to the direct excitation efficiency of the photoinitiator. The results demonstrate that the photosensitization process can be predicted, paving the way for further improvements in photoinitiating systems. [ABSTRACT FROM AUTHOR]

Development, rapid detection and quantification of anticancer drugs in biological samples are crucial for effective drug monitoring. The present work describes the design of a Hf(IV)‐based metal‐organic framework (MOF) (1) by the reaction between Hf(IV) ion and 2‐(thiophene‐2‐carboxamido)terephthalic acid linker with the surface area of 571 m2 g−1. Desolvated MOF (1′) displayed highly discriminative fluorescence sensing properties for the antineoplastic drug flutamide and biomolecule hemin in an aqueous medium in the presence of co‐existing biomolecules and ions. The MOF's response time for sensing flutamide and hemin was less than 5 s with low detection limits of 1.5 and 0.08 nM, respectively. Additionally, 1′ also demonstrated recyclability up to five cycles and maintained its sensing ability across different pH media, various water samples, and biological fluids. Experimental and theoretical analyses suggested photoinduced electron transfer and inner‐filter effect in the presence of flutamide and Förster resonance energy transfer in the presence of hemin are most likely reasons behind the fluorescence quenching of MOF. Furthermore, the MOF demonstrated catalytic activity in Friedel‐Crafts alkylation reactions, providing a 96 % yield with slight decay in its activity over four uses. The enhanced activity of 1′ compared to Hf‐BDC and Hf‐BDC‐NH2 (BDC: 1,4‐benzenedicarboxylic acid) is due to the functionalized thiophene moieties through hydrogen bond donating sites, confirmed by a series of control experiments. [ABSTRACT FROM AUTHOR]

A tetraphenylethylene (TPE) derivative, TPEPhDAT, modified by diaminotriazine (DAT), was prepared by successive Suzuki–Miyaura coupling and ring-closing reactions. This compound exhibits aggregation-induced emission enhancement (AIEE) properties in the DMSO/MeOH system, with a fluorescence emission intensity in the aggregated state that is 5-fold higher than that of its counterpart in a dilute solution. Moreover, the DAT structure of the molecule is a good acceptor of protons; thus, the TPEPhDAT molecule exhibits acid-responsive fluorescence. TPEPhDAT was protonated by trifluoroacetic acid (TFA), leading to fluorescence quenching, which was reversibly restored by treatment with ammonia (on–off switch). Time-dependent density functional theory (TDDFT) computational studies have shown that protonation enhances the electron-withdrawing capacity of the triazine nucleus and reduces the bandgap. The protonated TPEPhDAT conformation became more distorted, and the fluorescence lifetime was attenuated, which may have produced a twisted intramolecular charge transfer (TICT) effect, leading to fluorescence redshift and quenching. MeOH can easily remove the protonated TPEPhDAT, and this acid-induced discoloration and erasable property can be applied in anti-counterfeiting. [ABSTRACT FROM AUTHOR]

A novel fluorescent nanofilm DBAP-ETTA has been developed for diethyl chlorophosphate (DCP) vapor detection with high sensitivity and selectivity. Its smooth, homogeneous structure and large Stokes shift enable significant fluorescence quenching upon DCP exposure. The protonation-based sensing mechanism makes it ideal for real-time, portable DCP vapor sensing. [ABSTRACT FROM AUTHOR]

2‐Aminopurine (2AP) is a fluorescent analog of adenine, and its unique properties make it valuable in various biochemical and biotechnological applications. Its fluorescence property probes local dynamics in DNA and RNA because stacking with the surrounding bases quench its fluorescence. 2AP‐labeled DNA or RNA sequences have been used for the detection of genetic mutations, viral RNA, or other nucleic acid‐based markers associated with diseases like cancer and infectious diseases. In this study, we isolated aptamers for 2AP using the library immobilization capture‐SELEX technique. A dominating aptamer family was isolated after 15 rounds of selection. The Kd values for the most abundant 2AP1 aptamer are 209 nM in a fluorescence assay and 72 nM in an isothermal titration calorimetry test. A 32 nM 2AP limit of detection was tested based on its intrinsic fluorescence change upon aptamer binding. Additionally, we conducted some mutation analysis. Furthermore, we tested the selectivity of this aptamer and discovered that it can bind adenine and adenosine with approximately 100‐fold lower affinity than 2AP. [ABSTRACT FROM AUTHOR]

A new type of extended viologen, N,N′-2,5-bis(3-pyridinium)thiazolo[5,4-d]thiazole dipropionate, (m-H2TTzPA)(HSO3)2 (1), was synthesized, and two new coordination polymers, {[Cd(m-TTzPA)Br2]·H2O}n (2) and {[Zn(m-TTzPA)Br2]·H2O}n (3), were prepared based on the m-TTzPA ligand. Compounds 1–3 exhibit photochromic behaviors, which were proved using single-crystal X-ray diffraction, UV-vis spectroscopy and EPR characterizations. Furthermore, all the compounds have obvious fluorescence quenching behaviors upon irradiation using a xenon lamp, where compound 1 exhibits a significant quenching efficiency of 95.84%. [ABSTRACT FROM AUTHOR]

Following a new approach, we prepared a nanoink with two separate photothermally responsive absorption bands. One is the localized surface plasmon resonance (LSPR) absorption of gold nanoparticles (AuNP, d=17 nm), the second is the absorption band of two cyanine (Cy) dyes, Cy7‐C6 or Cy7‐C11, grafted to the AuNP surface through thiolated bridges of different lengths: the close proximity to the Au surface induces full quenching of the Cy fluorescence, resulting in thermal relaxation on irradiation. Attempts to full coat AuNP with the lipophilic Cy7‐C6 and Cy7‐C11 lead to precipitation from aqueous solutions. We thus prepared AuNP with partial pegylation (30, 50, or 70 %), using a long chain thiol‐terminated PEG bearing a ‐COOH function. Addition until saturation of either Cy7‐C6 or Cy7‐C11 to the partially pegylated AuNP gave the AuNP@Cy/PEGX% hybrids (X=30, 50, 70) that are stable in water and in the water/alcohol mixtures used to prepare the nanoinks. Further overcoating of AuNP@Cy7‐C6/PEG50 % with PAH (polyallylamine hydrochloride) avoids LSPR hybridization in the dry nanoink printouts, that present two separate bands. When irradiated with laser sources near their absorption maxima, the printouts of the AuNP@Cy7‐C6/PEG50 %@PAH nanoink respond on two channels, giving different temperature increases depending on the irradiation wavelengths. This enhances the potentiality of use of these nanoinks for photothermal anticounterfait printouts, making more difficult to reproduce the correct ΔT vs λirradiation output. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) are a burgeoning star of luminescent carbon‐based nanomaterials with emerging interest for various applications. Luminescence from the sp2‐conjugated domains in the carbon cores is considered to be the intrinsic bandgap emission of CDs, whereas the relationship between them remains poorly understood. Simultaneously, the solvent relaxation of water molecules will quench the fluorescence of CDs, thus, obtaining strong luminescence from CDs aqueous solutions remains a great challenge. Herein, a facile one‐step spatial‐confined cross‐condensation method that uses a heat‐induced self‐foaming process in ambient pressure has been developed to synthesize highly luminescent CDs with unprecedented photoluminescence quantum yield (PLQY) over 97.2% in water. The unique precursor‐derived cross‐arranged perylene skeleton in the cores hinders π–π stacking, while the hydrophobicity of the conjugated units mitigates solvent relaxation by water molecules, resulting in near‐unity PLQY in aqueous solutions, enabling this to demonstrate the first optically pumped green lasing emission in the CDs aqueous solution. Moreover, a biomaterial‐based white light emitting diode is fabricated using the CDs‐stained silks as a fluorescence conversion cover to realize a high luminous efficiency of 60.7 lm W−1 with CIE color coordinate of (0.33, 0.35). [ABSTRACT FROM AUTHOR]

Paraquat, an herbicide used to control annual and perennial weeds, poses risks to human, animal, and environmental health due to its toxicity. This article introduces a nanocontainer designed to bind and neutralize paraquat. The nanocontainer is a nanoscale sphere created through microemulsion polycondensation of resorcinarenes with tyrosine and carboxylate groups and phenylboronic acid. Transmission electron microscopy and dynamic light scattering indicate that the average size of the nanocontainer is approximately 300 nm. Fluorescence and NMR spectroscopy show that the nanocontainer binds paraquat, resulting in a shift of proton signals towards higher fields and fluorescence quenching, with a binding constant of 28000 M−1. This interaction alters the electrochemical properties, contributing to toxicity. In the cyclic voltammetry analysis of paraquat, adding the nanocontainer after three reduction cycles eliminates the reduction peaks, indicating complete neutralization of paraquat. The article details the nanocontainers synthesis, physicochemical properties, binding efficiency of paraquat, and its impact on electrochemical behavior, as well as potential applications for mitigating paraquats harmful effects. [ABSTRACT FROM AUTHOR]

A novel ratiometric fluorescent assay was proposed for protamine and heparin based on blue‐emitting N,P‐doped carbon dots (N,P‐CDs) and green‐emitting Eosin Y. The N,P‐CDs were prepared using arginine as carbon and nitrogen sources according to hydrothermal method with favorable luminescence intensity, photostability, and good reproducibility. And the N,P‐CDs were used as internal reference fluorescence molecules. The anionic Eosin Y was used as fluorescence signal molecule. Protamine with positive group could interact with Eosin Y through electrostatic effect, leading to the fluorescence quenching of Eosin Y. Upon the addition of heparin, heparin was combined with protamine with stronger affinity through electrostatic interactions and hydrogen bonds, which preventing the bonding of protamine with Eosin Y and obvious fluorescence emissions of Eosin Y at 538 nm could be observed. Meanwhile, the fluorescence signal of N,P‐CDs at 420 nm remained stable during the whole process. A good linear range between the fluorescence emission intensity ratio of I538/I420 was obtained for protamine from 0.01 to 40 μg/mL with a low detection limit of 5.6 ng/mL, and heparin from 0 to 35 μg/mL with a low detection limit of 2.5 ng/mL. Moreover, the method was further applied to detection of heparin with satisfactory results in fetal bovine serum samples. [ABSTRACT FROM AUTHOR]

A three‐dimensional (3D) anionic cadmium‐organic framework, namely [(CH3)2NH2][Cd1.5(DMTDC)2] ⋅ 2DMA ⋅ 0.5H2O (Cd‐MOF; DMA=N,N‐dimethylacetamide), was successfully synthesized under solvothermal conditions by using a linear thienothiophene‐containing dicarboxylate ligand, 3,4‐dimethylthieno [2,3‐b]‐thiophene‐2,5‐dicar‐boxylic acid (H2DMTDC). Single‐crystal X‐ray diffraction analysis reveals that Cd‐MOF exhibits a 3D anionic framework with pcuα‐Po topology, featuring rectangle and rhombus‐shaped channels along b‐ and c‐ axis direction. Cd‐MOF demonstrates selective adsorption of cationic dyes over anionic and neutral dyes. Additionally, Tb3+‐loaded Cd‐MOF serves as a fast‐response fluorescence sensor for the sensitive detection of Fe3+ ions with a low limit of detection (8.90×10−7 M) through fluorescence quenching. [ABSTRACT FROM AUTHOR]

It is a fluorescence-based study to examine the interaction between L-tryptophan and a selection of aldehydes, namely furfural (furan-2-carbaldehyde), 3-hydroxybenzaldehyde, salicylaldehyde (2-hydroxybenzaldehyde), 3-nitrobenzaldehyde, and 4-bromobenzaldehyde. The investigation took place in an aqueous environment, revealing that all five aldehydes induced quenching of the fluorescence intensity of L-tryptophan. By employing the Stern-Volmer equation to describe the quenching process, we constructed Stern-Volmer plots and derived Stern-Volmer constants. These constants (KSV) ranged from 2.87 × 104 mol L− 1 to 5.75 × 104 mol L− 1. Notably, the values of the Stern-Volmer constants varied among the different aldehydes, with the following order: 3-hydroxybenzaldehyde(3-HBA) > 4-bromobenzaldehyde (4-BBA) > 3-nitrobenzaldehyde > furan-2-carbaldehyde > salicylaldehyde. Consequently, our findings highlighted 3-hydroxybenzaldehyde as the most potent quencher, while 2-hydroxybenzaldehyde displayed the least sensitivity to quenching. Additionally, we determined the detection and quantification limits for the investigated aldehydes, resulting in ranges of 3.87 × 10− 12 to 8.25 × 10− 6 and 1.29 × 10− 11 to 2.75 × 10− 5, respectively. This research paves the way for the development of novel fluorescence probe-based sensors and offers valuable techniques for analyzing aldehydes within environmental and biological samples. [ABSTRACT FROM AUTHOR]

For the synthesis of heteroatom-doped carbon nanostructures, biomass is considered as a promising option. Utilizing the microwave-assisted method, we have demonstrated an easy and straightforward one-pot synthesis of nitrogen-doped luminous carbon dots (NCDs) from jamun seed powder and guanidine hydrochloride. Structural and morphological analyses were performed using various analytical techniques. Under ultraviolet light of 315 nm, NCDs emit a bright blue fluorescence, possess a high quantum yield of 26.90%, exhibit strong water dispersion, and demonstrated excellent stability. The average particle size of the NCDs was found to be 7.5±1.2 nm, with a spherical shape. NCDs exhibit high selectivity and sensitivity in fluorescence quenching when exposed to Mn7+ ions. Over a concentration range of 2–30 µM, the fluorescence response (F0/F) shows a linear relationship with Mn7+ concentration, with a detection limit of 0.81 µM. The probe exhibited negligible interference and proved to be effective in accurately quantifying Mn7+ in spiked real-water samples. [ABSTRACT FROM AUTHOR]

This paper scrutinises the development of low-cost hypersensitive fluorescent probes manipulated chemically with Schiff base complexes and their prospective applicability for the detection of nitro explosives in light of the rapidly expanding demand for anti-trafficking measures. In this study, a new Zn(II) metal complex has been synthesized in one pot using the Schiff base ligand L= 2-methoxy-5-methyl-N-(2-pyridin-2-ylmethylene) aniline. The complex was also thoroughly characterised using various spectroscopic tools and subjected to single crystal XRD analysis. In the asymmetric unit, square pyramidal zinc (II) centre exist in the inner N2O compartment of the ligand L. The intermolecular Cg···Cg interactions exist between two different asymmetric residual units lead to supramolecular assembly along b axis. By turning off the fluorescence response, the complex serves as a sensor for the detection of nitro aromatics in CH3CN solution. A significant quenching efficiency has been reported with a quenching constant (KSV) 1.8 × 104 M-1 for 4-nitrobenzoic acid during investigation of sensing phenomenon in solution phase. In addition, determining the binding stoichiometry of the chemosensor with NO2 and the binding constant, the mechanism of fluorescence quenching has also been postulated. The detection limit of NO2 is 7.6×10 -7 M, with the binding constant k = 1.1021× 108 M-1. Additionally, the DFT calculation makes it easier to comprehend the appropriate binding process in light of the findings of experiments. We also designed a paper sensor strip for the visual detection of Nitro Explosive Residues in light of the sensor's potential used in forensic investigations. [ABSTRACT FROM AUTHOR]

A fluorescent and colorimetric dual-mode strategy based on carbon dots (CDs) was rationally designed for sensitive determination of Cu2+. Green fluorescent CDs with high absolute quantum yield of 72.9% were synthesized by facile one-step hydrothermal treatment of triethylenetetramine and Rose Bengal. Cu2+ could trigger the oxidative and chromogenic reaction of p-phenylenediamine (PPD) to generate chromogenic PPDox, accompanied by the fluorescence quenching of the CDs. The quenching mechanism was identified as the inner filter effect between PPDox and CDs. Therefore, a colorimetric/fluorescent dual-mode detection method for Cu2+ recognition was constructed. The limits of detection for Cu2+ were 4.14 μM and 1.28 μM for colorimetric and fluorescent mode, respectively. In addition, this method had achieved satisfactory results in the detection of Cu2+ in real serum samples. [ABSTRACT FROM AUTHOR]

A dual-emission ratiometric fluorescence sensor (CDs@CdTe@MIP) with a self-calibration function was successfully constructed for AMO detection. In the CDs@CdTe@MIP system, non-imprinted polymer-coated CDs and molecule-imprinted polymer-coated CdTe quantum dots were used as the reference signal and response elements, respectively. The added AMO quenched the fluorescence of the CdTe quantum dots, whereas the fluorescence intensity of the CDs remained almost unchanged. The AMO concentration was monitored using the fluorescence intensity ratio (log(I647/I465)0/(I647/I465)) to reduce interference from the testing environment. The sensor with a low detection limit of 0.15 μg/L enabled detection of the AMO concentration within 6 min. The ratiometric fluorescence sensor was used to detect AMO in spiked pork samples; it exhibited a high recovery efficiency and relative standard deviation (RSD) of 97.94–103.70% and 3.77–4.37%, respectively. The proposed highly sensitive and selective platform opens avenues for sensitive, reliable, and rapid determination of pharmaceuticals in the environment and food safety monitoring using ratiometric sensors. [ABSTRACT FROM AUTHOR]

A smartphone-assisted portable dual-mode immunoassay was constructed based on curcumin nanoparticles (CNPs) and carbon dots (CDs) for gentamicin (GEN) detection. CNPs were labeled with goat anti-mouse IgG (Ab2) to create a conjugation that coupled dual signals to concentrations of GEN antigens. CNPs were introduced to pH 7.4 water and showed insignificant color and optical responses. When exposed to the high pH environment, the structure of CNPs changed and color and optical properties were restored. Because of the inner filter effect (IFE) between CNPs and CDs, the fluorescence of CNPs at 550 nm quenched the fluorescence of CDs at 450 nm. Colorimetry and ratiometric fluorescence (F550 nm/F450 nm) dual-mode immunoassay linearly correlated with GEN ranged from 10−4 to 100 µg/mL with a detection limit (LOD) of 8.98 × 10−5 µg/mL and 4.66 × 10−5 µg/mL, respectively. This work supplied a portable, sensitive, and specific platform to detect GEN. [ABSTRACT FROM AUTHOR]

Teicoplanin has been banned in the veterinary field due to the drug resistance of antibiotics. However, teicoplanin residue from the antibiotic abuse of humans and animals poses a threat to people's health. Therefore, it is necessary to develop an efficient way for the highly accurate and reliable detection of teicoplanin from humans, food, and water. In this study, novel imprinted quantum dots of teicoplanin were prepared based on boronate affinity-based precisely controlled surface imprinting. The imprinting factor (IF) for teicoplanin was evaluated and reached a high value of 6.51. The results showed excellent sensitivity and selectivity towards teicoplanin. The relative fluorescence intensity was inversely proportional to the concentration of teicoplanin, in the range of 1.0–17 μM. And its limit of detection (LOD) was obtained as 0.714 μM. The fluorescence quenching process was mainly controlled by a static quenching mechanism via the non-radiative electron-transfer process between QDs and the five-membered cyclic boronate esters. The recoveries for the spiked urine, milk, and water samples ranged from 95.33 to 104.17%, 91.83 to 97.33, and 94.22 to 106.67%, respectively. [ABSTRACT FROM AUTHOR]

Polyimide (PI) refers to a type of high-performance polymer containing imide rings in the main chain, which has been widely used in fields of aerospace, microelectronic and photonic devices, gas separation technology, and so on. However, traditional aromatic PIs are, in general, the inefficient fluorescence or even no fluorescence, due to the strong inter- and intramolecular charge transfer (CT) interactions causing unavoidable fluorescence quenching, which greatly restricts their applications as light-emitting functional layers in the fabrication of organic light-emitting diode (OLED) devices. As such, the development of fluorescent PIs with high fluorescence quantum efficiency for their application fields in the OLED is an important research direction in the near future. In this review, we provide a comprehensive overview of fluorescent PIs as well as the methods to improve the fluorescence quantum efficiency of PIs. It is anticipated that this review will serve as a valuable reference and offer guidance for the design and development of fluorescent PIs with high fluorescence quantum efficiency, ultimately fostering further progress in OLED research. [ABSTRACT FROM AUTHOR]

Rapid detection of potentially toxic heavy metals like Hg(II) has attracted great attention in the last few decades due to the importance to maintain a safe and sustainable environment for human beings. Coordination chemistry and concepts therein, play an important role in the detection of Hg(II). Size, charge, and nature of the donor atom and the respective cation (metal ion), are crucial in selective interactions between the sensor and metal ions. The sensors designed for the purpose, coordinate to Hg(II) ion through various donor sites, coordination causes a change in the electron density in organic molecules and results in either visible color change or enhancing/quenching fluorescence intensity. Since Hg(II) is soft metal, with d10 electron system, so majority of the sensors have soft donor sites which prefer to coordinate with Hg(II). Oxygen is also present in some chelating ligands which is least preferred coordination site, due to its hard nature. There are several reports of replacing other ligating sites by sulfur for enhanced mercury sensing. In some cases, desulfurization is being detected as clear change in spectral behavior during the sensing process. Efforts are still in progress to design and introduce a sensor with utmost sensitivity and selectivity. In this review, we made an attempt to explain the coordination aspects of Hg(II) detectors, reasons for poor efficiency and possible suggestions to improve the selection criterion of various compounds. It will help researchers to know about important concepts in designing more sensitive and selective sensors for detection of Hg(II) in environmental and biological samples. [ABSTRACT FROM AUTHOR]

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Inhibitors of the serine protease furin have been widely studied as antimicrobial agents due to their ability to block the cleavage and activation of certain viral surface proteins and bacterial toxins. In this study, the antipseudomonal effects and safety profiles of the furin inhibitors MI-1851 and MI-2415 were assessed. Fluorescence quenching studies suggested no relevant binding of the compounds to human serum albumin and α1-acid glycoprotein. Both inhibitors demonstrated significant antipseudomonal activity in Madin–Darby canine kidney cells, especially compound MI-1851 at very low concentrations (0.5 µM). Using non-tumorigenic porcine IPEC-J2 cells, neither of the two furin inhibitors induced cytotoxicity (CCK-8 assay) or altered significantly the intracellular (Amplex Red assay) or extracellular (DCFH-DA assay) redox status even at a concentration of 100 µM. The same assays with MI-2415 conducted on primary human hepatocytes also resulted in no changes in cell viability and oxidative stress at up to 100 µM. Microsomal and hepatocyte-based CYP3A4 activity assays showed that both inhibitors exhibited a concentration-dependent inhibition of the isoenzyme at high concentrations. In conclusion, this study indicates a good safety profile of the furin inhibitors MI-1851 and MI-2415, suggesting their applicability as antimicrobials for further in vivo investigations, despite some inhibitory effects on CYP3A4. [ABSTRACT FROM AUTHOR]

The ratiometric fluorescent probe UiO-OH@Tb, a zirconium-based MOF functionalized with Tb3+, was synthesized using a hydrothermal method. This probe employs the fluorescence resonance energy transfer (FRET) mechanism between Tb3+ and malachite green (MG) for the double-inverse signal ratiometric fluorescence detection of MG. The probe's color shifts from lime green to blue with an increasing concentration of MG. In contrast, the monometallic MOFs' (UiO-OH) probe shows only blue fluorescence quenching due to the inner filter effect (IFE) after interacting with MG. Additionally, the composite fluorescent probe (UiO-OH@Tb) exhibits superior sensitivity, with a detection limit (LOD) of 0.19 μM, which is significantly lower than that of the monometallic MOFs (25 μM). Moreover, the content of MG can be detected on-site (LOD = 0.94 μM) using the RGB function of smartphones. Hence, the UiO-OH@Tb probe is proven to be an ideal material for MG detection, demonstrating significant practical value in real-world applications. [ABSTRACT FROM AUTHOR]

A highly sensitive and selective fluorescent probe utilizing B and S co-doped graphene quantum dots (BS-GQDs) has been created for detecting ibuprofen. The co-doping strategy effectively modulated the electronic structure and surface properties of GQDs, resulting in enhanced fluorescence quantum yield and sensing performance. The BS-GQDs exhibited strong fluorescence quenching upon interaction with ibuprofen, which was attributed to the formation of a ground-state complex and electron transfer from BS-GQDs to ibuprofen. Under optimal conditions, the sensor exhibited a broad linear range, a low detection limit, and outstanding selectivity for ibuprofen compared to other common medications and interferents. The practical utility of the sensor was validated through the successful identification of ibuprofen in spiked urine and serum samples, achieving high recovery rates and accuracy. The BS-GQDs-based fluorescent sensor provides a promising platform for sensitive, rapid, and reliable monitoring of ibuprofen in pharmaceutical and biomedical fields.

In present work, blue carbon dots (b-CDs) were derived from ammonium citrate and guanidine hydrochloride, and red carbon dots (r-CDs) were stemmed from malonate, ethylenediamine and meso‑tetra (4-carboxyphenyl) porphin based on facile hydrothermal method. Eco-friendly ratiometric fluorescence probe was innovatively constructed to effectively measure Hg2+ utilizing b-CDs and r-CDs. The developed probe displayed two typical emission peaks at 450 nm from b-CDs and 650 nm from r-CDs under the excitation at 360 nm. Mercury ion has strong quenching effect on the fluorescence intensity at 450 nm due to the electron transfer process and the fluorescence change at 450 nm was used as the response signal, whereas the fluorescence intensity at 650 nm kept unchangeable which resulted from the chemical inertness between Hg2+ and r-CDs, serving as the reference signal in the sensing system. Under optimal circumstances, this probe exhibited an excellent linearity between the fluorescence response values of ΔF 450 /F 650 and Hg2+ concentrations over range of 0.01–10 µmol/L, and the limit of detection was down to 5.3 nmol/L. Furthermore, this probe was successfully employed for sensing Hg2+ in practical environmental water samples with satisfied recoveries of 98.5%–105.0%. The constructed ratiometric fluorescent probe provided a rapid, environmental-friendly, reliable, and efficient platform for measuring trace Hg2+ in environmental field. [ABSTRACT FROM AUTHOR]

In this paper, a smartphone-assisted detection integrated with paper-based analytical device (PAD) functionalised with green emissive carbon dot (g-CDs) has been designed for on-site selective detection of Fe3+ ions. g-CDs have been prepared by one-step hydrothermal process using 4-aminophenol and ethylenediamine (EDA) as precursors. g-CDs were highly stable for more than three months in aqueous solution with a strong green emission, λem at 513 nm and 30.33% as a fluorescence quantum yield. Interestingly, Fe3+ selectively quenched the fluorescence intensity of the g-CDs and the quenching mechanism can be attributed to static quenching. Furthermore, under the optimal conditions, using conventional fluorimetry, the g-CDs could detect Fe3+ ions with a linear relationship from 0 to 90 μM (R2 = 0.9970) and the limit of detection was 0.35 μM. Visual mode integrated with smartphone detection on PAD was successfully prepared after loading g-CDs on the paper. The fluorescent colour variations of g-CDs on PAD were monitored under the UV lamp using smartphone for capturing images. The green channel intensities of images of the circle zones were processed using Colour Grab App for the RGB analysis. A linear working range was obtained from 0 to 0.8 mM, and the limit of detection was 0.05 mM. The PAD was used successfully for the detection of Fe3+ ions in human serum with a recovery from 87.93% to 96.86%. [ABSTRACT FROM AUTHOR]

Given the widespread and diverse effects of transition metal ions such as copper and zinc in multiple biological processes, this research endeavor addresses herein the microwave‐aided synthesis of two novel tetradentate ONNO (L1) and tridentate NNO (L2) donor Schiff base ligands derived from 4,5‐dimethyl‐1,2‐phenylenediamine and 4‐bromo‐2‐hydroxybenzaldehyde in a 1:2 ratio and from 4,5‐dimethyl‐1,2‐phenylenediamine and 5‐methoxy‐2‐hydroxybenzaldehyde in a 1:1 ratio, with their respective zinc, ZnL1(1) and ZnL2(3), and copper, CuL1(2) and CuL2(4), Schiff base metal complexes, which are comprehensively characterized utilizing physiochemical and analytical techniques, along with geometry optimization using the DFT approach. Spectrophotometric analyses have been used to assess the biomimetic activity in the conversion of 3,5‐DTBC to 3,5‐DTBQ with turnover numbers 53.4 and 78 h−1 in methanol for 2 and 4, whereas the zinc complexes are found to be ineffective. With CT‐DNA, possible modes of interaction with the synthesized complexes have been explored using absorption spectroscopy, where the associated binding constants ranged between 1.541 × 105 and 2.186 × 105 M−1. EtBr‐bound DNA was used in the fluorescence quenching experiments with Stern–Volmer constant (Ksv) values in the range 4.084 × 104 and 3.402 × 104 M−1, showing a stronger association with CT‐DNA. The compounds' ability to inhibit bacterial strains was also examined in vitro, as well as their ability to reduce inflammation, through the protein denaturation method and the DPPH assay for antioxidant activity have been performed. Furthermore, molecular docking simulations have been carried out to obtain a deeper comprehension of the molecular‐level interactions with CT‐DNA and cyclooxygenase‐2 (COX‐2). [ABSTRACT FROM AUTHOR]

In the field of water decontamination, the design of luminance sensor for sensitive detection of heavy metal ion toxic and nitroaromatic compounds are important and challenging. Herein, a new luminescent Cd(II) metal–organic framework (MOF), {[Cd2(H2O)3(4‐CPCA)2]·2H2O}n (SNUT‐27) (H2(4‐CPCA) = 1‐(4‐carboxyphenyl)‐4‐oxo‐1,4‐dihydropyridazine‐3‐carboxylic acid) was obtained by the reaction of flexible ligand H2(4‐CPCA) and Cd(II) ions, characterized by single crystal X‐ray diffraction, PXRD, FT‐IR, and TGA, the samples were further analyzed. The analysis of single crystal X‐ray diffraction showed that SNUT‐27 possesses a distinct three‐dimensional spatial arrangement and demonstrates impressive fluorescence properties. Particularly, SNUT‐27 showed a highly sensitive response to the nitro‐aromatic compounds nitrobenzene by fluorescence quenching, and in contrast, showed a fluorescence enhancement response to Al3+ and Cu2+. SNUT‐27 can be effortlessly recycled by simply rinsing with water post‐sensing experiments, showcasing its reusability. Additionally, potential detection mechanisms have been explored. [ABSTRACT FROM AUTHOR]