Nile Red Research Articles

Ruthenium complexes bearing nile red chromophore and one of its derivative: Theoretical evaluation of PDT-related properties.

The outcomes of DFT-based calculations are here reported to assess the applicability of two synthesized polypyridyl Ru(II) complexes, bearing ethynyl nile red (NR) on a bpy ligand, and two analogues, bearing modified-NR, in photodynamic therapy. The absorption spectra, together with the non-radiative rate constants for the S1 - Tn intersystem crossing transitions, have been computed for this purpose. Calculations evidence that the structural modification on the chromophore destabilizes the HOMO of the complexes thus reducing the H-L gap and, consequently, red shifting the maximum absorption wavelength within the therapeutic window, up to 620 nm. Moreover, the favored ISC process from the bright state involves the triplet state closest in energy, which is also characterized by the highest SOC value and by the involvement of the whole bpy ligand bearing the chromophore in delocalising the unpaired electrons. These outcomes show that the photophysical behavior of the complexes is dominated by the chromophore.

Quercetin ameliorates lipid deposition in primary hepatocytes of the chicken embryo

ABSTRACT 1. The accumulation of excessive fat plays a role in the development of non-alcoholic fatty liver disease (NAFLD) and phytogenic feed additives have the potential to ameliorate this. This study involved the isolation and culture of primary hepatocytes from chicken embryos to establish a model of hepatic steatosis induced by oleic acid/dexamethasone (OA/DEX). Lipid accumulation and cell viability were assessed using Nile Red staining, Oil Red O staining and cell count Kit −8 (CCK8) following treatment with varying concentrations of quercetin (Que). The potential mechanism by which Que exerts its effects was preliminarily investigated. 2. The results indicated that OA effectively treated lipid accumulation in hepatocytes. There was no notable variance in cell proliferation between the normal and OA/DEX groups when subjected to Que treatment at concentrations of 1000 ng/ml and 10 000 ng/ml. Triglycerides and cholesterol (low and high density) decreased with Que treatment, with the most substantial reduction observed at 10 000 ng/ml. 3. Gene expression levels decreased to levels similar to those in the control groups. Western blot data demonstrated that sterol regulatory element-binding protein 1 (SREBP-1) protein expression correlated with its mRNA expression level. Que mitigated lipid accumulation through the alpha serine/threonine protein kinase (AKT) and extracellular signal-regulated kinase (ERK) pathways. Expression levels of lipid-related genes (APOB, PPARα, CYP3A5 and SREBP-1) decreased to levels similar to the control groups. Western blot data demonstrated that the SREBP-1 protein expression correlated with its mRNA expression level. 4. Supplementation with Que ameliorated lipid accumulation through AKT and ERK signalling pathway in OA/DEX-induced high-fat hepatocytes.

Synthesis of inverse push-pull coumarin dyes and their application as solvatochromic probes and labelling agents for bacterial cell membranes

Coumarin derivatives have been widely employed across a great number of applications, such as laser dyes, bioimaging or chemossensors, owing to their strong fluorescence and high-quantum yields. These properties are highly tunable through structural modification, namely by the inclusion of electron-withdrawing groups (EWG) and electron-donating groups (EDG) at positions 3 and 7 of the coumarin scaffold, respectively. Comparatively, there aren't many reports of EDGs being employed at position 3, prompting us to investigate this new class of potential fluorophores.We undertook the synthesis of three novel ethynyl-linked aminophenyl-coumarin dyes, employing a key Sonogashira-coupling reaction to introduce the electron-rich tertiary aniline moiety. Two different amine donors were used, diphenylamino (coumarins A and B) and dimethylamino (coumarin C), as well as two alkoxy substituents, dibenzyloxy (A and C) and methylenedioxy (B), in the phenyl ring of the coumarin. All dyes show strong emission and significant positive solvatochromism. Additionally, they were employed as staining agents for the cellular membrane of S. pneumoniae, a Gram-positive bacterial pathogen. None of the three derivatives presented cytotoxic effects. Only A and B successfully labelled the bacterial membrane. In the case of B a very similar staining pattern and performance to that of standard dye Nile Red was observed, while A seemed to possess a more selective distribution.

Environmental Homeopathy: Homeopathic Potencies Regulate the Growth and Toxicity of Raphidiopsis raciborskii (cyanobacteria) and Can be Tracked Physico-Chemically. Part 2: Physico-chemical Results.

The control of cyanobacterial toxicity and growth by homeopathic potencies was described in Part 1 of this two-part report. Here, a parallel approach characterized the physico-chemical features of the potencies used and the liquid media treated with them, correlating these results with their respective biological effects. Our objective was to establish if physico-chemical parameters can track homeopathic potencies in seawater or artificial seawater medium (ASM)-1 and to discover whether these parameters correlate with previously described biological effects. Artemia franciscana (brine shrimp) cysts were cultivated in seawater challenged with Raphidiopsis raciborskii extract and treated with different homeopathic potencies chosen from a screening process. Cultures of R. raciborskii maintained in ASM-1 were also treated with previously screened homeopathic potencies, and their growth was monitored as a function of time. The physico-chemical properties of the treated media (seawater or ASM-1) were evaluated by their interaction with solvatochromic dyes and changes in pH, conductivity and temperature. Coumarin 7 was found to be a marker for Nitric acidum 6cH and Isotherapic (R. raciborskii extract) 200cH in seawater (analysis of variance [ANOVA], p = 0.0015). Nile red was found to be a marker for Nitric acidum 200cH and Mercurius solubilis 30cH in ASM-1 (ANOVA, p ≤ 0.001). An increase in pH of ASM-1 and endothermic effects were observed after these treatments (two-way ANOVA, p = 0.0001). Seawater and ASM-1 to which potencies had been added were also subjected to a constant unidirectional 2,400 Gauss static magnetic field and found to have enhanced effects on the solvatochromic dyes tested. Homeopathic potencies were specifically traceable in aqueous media using solvatochromic dyes, especially when the samples were subjected to a magnetic field. Results from monitoring other physical parameters, such as pH and temperature, were less specific in relation to potency tracking. However, potency-induced endothermic effects might provide valuable thermodynamic data relating to the nature of potencies.

Enhancing Microplastics Recovery from Complex Sludge Samples Using COD-Guided Pretreatment

Given the society’s continuous reliance on plastic materials, large amounts of micron-sized plastic particles (i.e., microplastics, MPs) reach wastewater treatment plants (WWTPs) every day. Despite their effective removal from influent wastewater, over 90% of MPs in WWTPs are accumulated in sludge. Yet, there is no universally accepted method for quantifying and identifying MPs, obscuring our understanding of this pollution’s extent. Therefore, this study aims to develop a chemical oxygen demand (COD) based repeatable method for MPs analysis in sludge, which is a very complex, MPs-laden by product of WWTPs. The developed method is unique in that it removes the organic substances interfering with polymer analysis by monitoring the COD of sludge. Upon 90% of organic matter removal, MPs are extracted from the medium by a two-step density-based separation, sieved, stained with Nile Red, and counted using fluorescence microscopy. Moreover, quality assurance and quality control strategies including blank preparation and spike-and-recovery test procedures are followed. The protocol ensures a minimum 80% recovery rate of various MPs from both waste activated sludge (WAS) and wastewater samples, aligning with recommended standards. Crucially, the method preserves the chemical identity of MPs. Application of the protocol revealed that urban WWTP WAS had 475 MPs/g TS; industrial influent and effluents wastewater had 73 and 26 MPs/L; and industrial secondary and dewatered sludge had 114 and 132 MPs/g TS, consistent with the literature. This demonstrates the method’s robustness by revealing MPs reduction within the WWTP process and sludge accumulation as treatment progresses.Graphical

Advancements in laser-based spatiotemporal measurements of flow boiling

Recent advancements in laser and imaging systems, as well as in computational processing capabilities, have made quantitative optical imaging, which is often combined with laser illumination, highly adaptable, robust and reliable. Laser-based diagnostic techniques, such as planar laser-induced fluorescence (PLIF), offer the possibility of simultaneous spatiotemporally resolved measurements of temperature fields in the liquid phase at boiling conditions. In this paper, we examine the applicability of two-colour PLIF (2cPLIF), where the ratio between individual fluorescent emissions from uniformly dispersed dyes is used to take temperature measurements in the liquid phase in the presence of moving vapour-liquid interfaces typical of boiling flow. The implementation of 2cPLIF necessitates uniformity in the concentration of different dyes across the flow field. However, in the case of a multiphase flow such as boiling, thermophoresis can lead to inhomogeneous dye distributions. To overcome this challenge, a single-dye multispectral planar laser-induced fluorescence (SDMS-PLIF) method has been developed, which employs fluorescent emissions in different spectral bands of the same dye (Nile Red). The spectral characteristics of Nile Red were measured using a spectrometer to identify its temperature-sensitive bands over a wide range of dye concentrations, from 0.3 to 30 mg/L. Following this, we demonstrate the measurement capabilities of SDMS-PLIF thermography as applied to a boiling flow in a miniaturised vertical square channel, gaining insight into the thermohydrodynamic interactions between vapour bubbles and a heated wall.

Synthesis and Controlled Cargo Release of Novel Photoresponsive Polysiloxane‐Based Single‐Chain Nanoparticles

AbstractHerein, a novel, highly branched and photoresponsive polysiloxane is synthesized and studied. The polymer is photoconstructed into a single‐chain nanoparticle loaded with Nile Red and Metformin. Through the photoreversible [2+2] mechanism of the polymer's pendant coumarin moieties, the nanoparticles are de‐crosslinked, and their cargo molecules released. A study of the kinetics of release is undertaken in different solvents, providing insight into the relationship between the cargo's molecular structure and that of the polymer chain. On the whole, this report's study introduces new controlled release and cationic ring‐opening polymerization concepts while providing the first example of a single‐chain polymer nanoparticle based on a photoresponsive polysiloxane.

Cucurbituril‐Confined Tetracation Supramolecular 2D Organic Framework for Dual‐Emission TS‐FRET

AbstractHerein, cucurbituril‐regulated supramolecular multi‐dimensional organic framework constructed is reported by tetraphenylvinyl grafted bromophenylpyridine salt derivatives (TPE‐BrN) and cucurbit[n]uril (n = 6, 7, 8) via non‐covalent cross‐linked, giving supramolecular macrocycle‐confined fluorescence‐phosphorescence dual emission at 560 and 510 nm in solid state. Different from the formation of TPE‐BrN⊂CB[6] complexes and TPE‐BrN⊂CB[7] nanoparticle, TPE‐BrN⊂CB[8] manifested high‐efficient 2D network assembly. TPE‐BrN⊂CB[8] assembly can effectively activate triplet‐state to singlet‐state Förster resonance energy transfer (TS‐FRET) with long‐lived near‐infrared emission at 675 nm via doping organic dye Nile red (NiR) and the energy transfer efficiency reached up to 99%. Although CB[7] can also induce the typical phosphorescence emission at 510 nm, there is no TS‐FRET occurring after doping NiR into TPE‐BrN⊂CB[7] assembly due to the formation of different assembly modes. The multicolor long‐lived emission has been demonstrated very well based on the TS‐FRET process activated by CB[8] macrocyclic confined 2D organic framework, which can be successfully applied to fingerprint imaging and the construction of logic gate systems. It provides a novel method for supramolecular macrocycle confined phosphorescence regulation and the development of luminescent materials.

High throughput microfluidics-based synthesis of PEGylated liposomes for precise size control and efficient drug encapsulation

The low scalability and reproducibility of existing synthesis methods have hindered the translation of liposome nanoparticles as carriers for targeted drug delivery from conventional laboratory techniques to mass production. To this end, in this study, we present a high-throughput microfluidics-based approach for the synthesis of PEGylated liposomes with a primary focus on achieving precise size control and efficient encapsulation of hydrophobic drug molecules. In this platform, liposomes were self-assembled through a controllable mixing of lipids (EYPC, cholesterol, and DSPE-PEG 2000) dissolved in ethanol and an aqueous solution. The key parameters, including the chip design, total flow rate, flow rate ratio, lipid concentrations, as well as variations in buffer (HEPES and NaCl) and solvent composition (commercial and reagent-grade ethanol) were explored in detail. Through comprehensive parametric studies, we gained valuable insights into the influence of these variables on the size distribution of liposomes and succeeded in producing highly reproducible liposomes ranging from approximately 60 nm (corresponding to small unilamellar vesicles) to 150 nm (representing large unilamellar vesicles), all while maintaining a polydispersity index (PDI) of less than 0.2. To assess the encapsulation efficiency of hydrophobic drug molecules, Nile red (NR) was employed as a surrogate. We meticulously examined the impact of NR concentration on the drug encapsulation process, resulting in up to 74% drug encapsulation efficiency within the PEGylated liposomes. This research offers crucial advances in liposome synthesis and drug delivery, providing a high-throughput, controllable method for PEGylated liposomes with potential in pharmaceutical and biomedical fields.

Insights into the interaction and inhibitory action of palmatine on lysozyme fibrillogenesis: Spectroscopic and computational studies

Interaction under amyloidogenic condition between naturally occurring protoberberine alkaloid palmatine and hen egg white lysozyme was executed by adopting spectrofluorometric and theoretical molecular docking and dynamic simulation analysis. In spetrofluorometric method, different types of experiments were performed to explore the overall mode and mechanism of interaction. Intrinsic fluorescence quenching of lysozyme (Trp residues) by palmatine showed effective binding interaction and also yielded different binding parameters like binding constant, quenching constant and number of binding sites. Synchronous fluorescence quenching and 3D fluorescence map revealed that palmatine was able to change the microenvironment of the interacting site. Fluorescence life time measurements strongly suggested that this interaction was basically static in nature. Molecular docking result matched with fluorimetric experimental data. Efficient drug like interaction of palmatine with lysozyme at low pH and high salt concentration prompted us to analyze its antifibrillation potential. Different assays and microscopic techniques were employed for detailed analysis of lysozyme amyloidosis.Thioflavin T(ThT) assay, Congo Red (CR) assay, 8-anilino-1-naphthalenesulfonic acid (ANS) assay, Nile Red (NR) assay, anisotropy and intrinsic fluorescence measurements confirmed that palmatine successfully retarded and reduced lysozyme fibrillation. Dynamic light scattering (DLS) and atomic force microscopy (AFM) further reiterated the excellent antiamyloidogenic potency of palmatine.

Synthesis of pH/redox-double-responsive ferrocene-containing diblock copolymers and their application in controlled release

A novel pH/redox-double-responsive ferrocene-containing diblock copolymer of poly(ethylene glycol)-block-poly[2-(2-((2-ferrocenyl ethyl ester) (methyl) amino) ethoxy) ethyl methacrylate] [mPEG113-b-P(Fe–N-EOMA)] was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. mPEG113-b-P(Fe–N-EOMA) is amphiphilic with PEG as hydrophilic block and the part containing ferrocene as hydrophobic block. For comparison, three other diblock copolymers were prepared by changing the molecular weight of the hydrophilic block and the microstructure of the hydrophobic block. The diblock copolymers have a critical pH in solution and increases with the increase of the hydrophilicity of the copolymers. The redox-response was confirmed by the shift of characteristic peak of ferrocene in the UV/vis absorption spectrum after adding FeCl3/VC. The self-assembly behavior of these diblock copolymers in solution were then investigated. It shows that they have low critical micelle concentration (cmc), and the cmc decreases as the hydrophobicity of copolymers increases. Their morphology is varied, including sphere, lamella, aggregated sphere, and can be reversible changed by the stimulation of pH and redox. Finally, mPEG113-b-P(Fe–N-EOMA) was applied to the release of Nile Red (NR), which showed a good release efficiency. The prepared diblock copolymers have sensitive and reversible response properties, which provided ideas for the design of multistimuli-responsive polymers, and have good application prospects in drug-release.

The carbon dots based on Nile red: The preparation and application to probe α-synuclein fibrils

The aggregation of α-synuclein often links to the occurrence and development of Parkinson’s disease (PD). It is crucial to detect the α-synuclein fibril or monitor the aggregation of monomer for pharmacological and pathological researches, drug development and clinical diagnosis, etc. In this study, the Nile red (NR)-based carbon dots (NR-CDs) were meticulously designed and prepared. The NR-CDs were sensitive to the microenvironment, exhibiting enhanced fluorescence intensity with the elevated viscosity and decreased polarity. Thus, the NR-CDs exhibited high affinity towards α-synuclein fibril with remarkable red fluorescence enhancement, but did not respond to its monomer. Hence, the NR-CDs were used as the turn-on fluorescence probe to detect and image α-synuclein fibrils both in vitro and in vivo, as well as to monitor the aggregation process of the amyloids. Superior to NR dye, NR-CDs were characteristic of lower toxicity, better water dispersibility and anti-photobleaching resistance. In addition, the NR-CDs were demonstrated to inhibit the aggregation of α-synuclein, holding the potential as the therapeutic agent. The present study provided an effective way of designing the CDs using the small molecular dye as the carbon source to improve the biocompatibility and detectability, while reserve the selective turn-on fluorescence towards amyloid aggregates. This strategy may be generalized to construct more fluorescence probes with desired properties.

Microplastics in personal care products and cosmetics in Sri Lanka

In the Sri Lankan context, the lack of baseline studies to mitigate microplastic emissions through personal care and cosmetic products poses a huge problem. Hence this study serves as the first scientific investigation to analyze and characterize microplastics in selected personal care and cosmetic items available in the Sri Lankan markets. Fifteen brands representing five categories (face wash, facial scrubs, baby creams, shaving creams, and skin creams) of personal care and cosmetic items served as the basis for this investigation. Based on a questionnaire survey, from each category, three highly utilized brands were chosen and triplicates from each brand were used for the analysis. All samples were treated with the Fenton reagent to extract microplastics. Then through Nile red staining suspected microplastic were screened and characterized through FT-IR spectroscopy. The Nile Red analysis revealed seven brands of the fifteen to be stained with Nile Red and demonstrate luminance properties under UV light. However, FT-IR analysis proved only six brands contained actual microplastics. Low-density polyethylene and ethylene-propylene copolymer were the dominant types of microplastic. Most microplastics were irregularly shaped and white in color with sizes ranging from 238.55 ± 50.74 to 450.69 ± 174.9 μm. An emission estimation revealed that products FS-01 and FW-03 contain 3.36 ± 0.20 g and 0.2 ± 0.05 g of isolatable microplastics per product. While the present study provides scientific evidence for the availability of microplastics in products in Sri Lankan markets, it also provides a great opportunity to develop relevant policies and regulations to control them.

The pFSH dose affects the efficiency of in vivo embryo production in Santa Inês ewes

This study compared the follicular growth, superovulatory response, and in vivo embryo production after administering two doses of porcine follicle-stimulating hormone (pFSH) in Santa Inês ewes. The estrous cycle of 36 multiparous ewes was synchronized with the Day 0 protocol and superovulated with 133 mg (G133, n=18) or 200 mg (G200, n=18) of pFSH. Ultrasonographic evaluations of the ovaries were performed, ewes were mated and submitted to non-surgical embryo recovery. Viable blastocysts were stained with Nile Red and Hoechst. The G200 had a greater number of medium and large follicles, as well as a larger size of the third largest follicle. A total of 97.2% (35/36) of the ewes came into estrus and it was possible to transpose cervix in 80.6% (29/36). There were no effects of treatments in the response to superovulation, the proportion of ewes in which was possible to transpose the cervix, the number of corpora lutea, the number of anovulatory follicles, the proportion of ewes flushed with at least one recovered structure, number of recovered structures, number of viable embryos, viability rate, and recovery rate. The G200 ewes were in estrus for a longer period of time than the G133 ewes (54.0 ± 4.5 h vs. 40.3 ± 3.6 h) and produced more freezable embryos (6.5 ± 1.6 vs. 2.3 ± 0.7) than G133. Both doses promoted an efficient superovulatory response and did not affect embryonic lipid accumulation. The dose of 200 mg of pFSH showed greater potential to increase the superovulatory response, as it increased follicular recruitment and the recovery of freezable embryos.

Dynamic Mode Decomposition of Multiphoton and Stimulated Emission Depletion Microscopy Data for Analysis of Fluorescent Probes in Cellular Membranes.

An analysis of the membrane organization and intracellular trafficking of lipids often relies on multiphoton (MP) and super-resolution microscopy of fluorescent lipid probes. A disadvantage of particularly intrinsically fluorescent lipid probes, such as the cholesterol and ergosterol analogue, dehydroergosterol (DHE), is their low MP absorption cross-section, resulting in a low signal-to-noise ratio (SNR) in live-cell imaging. Stimulated emission depletion (STED) microscopy of membrane probes like Nile Red enables one to resolve membrane features beyond the diffraction limit but exposes the sample to a lot of excitation light and suffers from a low SNR and photobleaching. Here, dynamic mode decomposition (DMD) and its variant, higher-order DMD (HoDMD), are applied to efficiently reconstruct and denoise the MP and STED microscopy data of lipid probes, allowing for an improved visualization of the membranes in cells. HoDMD also allows us to decompose and reconstruct two-photon polarimetry images of TopFluor-cholesterol in model and cellular membranes. Finally, DMD is shown to not only reconstruct and denoise 3D-STED image stacks of Nile Red-labeled cells but also to predict unseen image frames, thereby allowing for interpolation images along the optical axis. This important feature of DMD can be used to reduce the number of image acquisitions, thereby minimizing the light exposure of biological samples without compromising image quality. Thus, DMD as a computational tool enables gentler live-cell imaging of fluorescent probes in cellular membranes by MP and STED microscopy.

Resolving the Nanoscale Structure of β-Sheet Peptide Self-Assemblies Using Single-Molecule Orientation-Localization Microscopy.

Synthetic peptides that self-assemble into cross-β fibrils are versatile building blocks for engineered biomaterials due to their modularity and biocompatibility, but their structural and morphological similarities to amyloid species have been a long-standing concern for their translation. Further, their polymorphs are difficult to characterize by using spectroscopic and imaging techniques that rely on ensemble averaging to achieve high resolution. Here, we utilize Nile red (NR), an amyloidophilic fluorogenic probe, and single-molecule orientation-localization microscopy (SMOLM) to characterize fibrils formed by the designed amphipathic enantiomers KFE8L and KFE8D and the pathological amyloid-beta peptide Aβ42. Importantly, NR SMOLM reveals the helical (bilayer) ribbon structure of both KFE8 and Aβ42 and quantifies the precise tilt of the fibrils' inner and outer backbones in relevant buffer conditions without the need for covalent labeling or sequence mutations. SMOLM also distinguishes polymorphic branched and curved morphologies of KFE8, whose backbones exhibit much more heterogeneity than those of typical straight fibrils. Thus, SMOLM is a powerful tool to interrogate the structural differences and polymorphism between engineered and pathological cross-β-rich fibrils.

Precision Loading and Delivery of Molecular Cargo by Size-Controlled Coacervation of Gold Nanoparticles Functionalized with Elastin-like Peptides.

Thermoresponsive elastin-like peptides (ELPs) have been extensively investigated in biotechnology and medicine, but little attention has been paid to the process by which coacervation causes ELP-decorated particles to aggregate. Using gold nanoparticles (AuNPs) functionalized with a cysteine-terminated 96-repeat of the VPGVG sequence (V96-Cys), we show that the size of the clusters that reversibly form above the ELP transition temperature can be finely controlled in the 250 to 930 nm range by specifying the concentration of free V96-Cys in solution and using AuNPs of different sizes. We further find that the localized surface plasmon resonance peak of the embedded AuNPs progressively red-shifts with cluster size, likely due to an increase in particle-particle contacts. We exploit this fine control over size to homogeneously load precise amounts of the dye Nile Red and the antibiotic Tetracycline into clusters of different hydrodynamic diameters and deliver cargos near-quantitatively by deconstructing the aggregates below the ELP transition temperature. Beyond establishing a key role for free ELPs in the agglomeration of ELP-functionalized particles, our results provide a path for the thermally controlled delivery of precise quantities of molecular cargo. This capability might prove useful in combination photothermal therapies and theranostic applications, and to trigger spatially and temporally uniform responses from biological, electronic, or optical systems.

Tracking of uranium and thorium natural distribution in the chemical fractions of the Nile Valley and the Red Sea phosphorites, Egypt

The present study aims to elucidate the possible sources of uranium and thorium content in the Campanian–Maastrichtian phosphorites from the Duwi Formation in the Nile Valley and Red Sea by conducting facies analysis and sequential leaching method. Nile Valley samples were collected from the El-Sibaiya East area, while those of the Red Sea were collected from two locations: Hamadat and Zug El Bahar. The petrographic investigation revealed that the Sibaiya East phosphorites exhibit peloidal bioclastic phospharenite–phospharudite microfacies, while Hamadat and Zug El Bahar phosphorites display peloidal bioclastic phosphalutite and silicified peloidal bioclastic phospharenite microfacies, respectively. Besides, U–Th bearing accessory minerals, such as zircon and monazite occur in Sibaiya East phosphorites. Thorium is present in Zug El Bahar phosphorites as minute accumulations associating apatite and quartz. Moreover, uranium is found with vanadium and iron as fine patches in the Sibaiya East phosphorite, and as small disseminations associated with Ca and Si in the Hamadat phosphorite. The X-ray diffraction shows that the investigated phosphorites are essentially built up of hydroxyl apatite Ca5(PO4)3(OH) and quartz SiO2. To accurately evaluate the bioavailability and mobility of uranium and thorium in the investigated phosphorites, it was necessary to identify the overall concentration and the various chemical forms of these elements by a five-step sequential leaching technique. The results indicate that Th and U are more abundant in the Red Sea phosphorites than in the Nile Valley phosphorites. Furthermore, Th is not bio-available and it is mostly found in the residue as Th-bearing minerals. Uranium, unlike Th is bio-available and fractionates among all fractions, indicating that U accumulation is the result of various diagenetic processes.

A novel supramolecular assembly based on nor-seco-cucurbit[10]uril for spermine sensing and artificial light-harvesting

A supramolecular assembly composed of perylene diimide derivative (PDI-nm) and nor-seco-cucurbit[10]uril (ns-Q[10]) was designed. The excellent host-guest interaction between PDI-nm and ns-Q[10] prevented the aggregation-caused quenching (ACQ) effect of PDI-nm, resulting in a luminescent assembly. The addition of spermine to the PDI-nm/ns-Q[10] assembly restored the ACQ of PDI-nm due to the competitive binding of spermine to ns-Q[10], which released PDI-nm. The assembly based on this principle showed ultra-high sensitivity for the detection of spermine with a detection limit as low as 7.84 × 10−7 mol/L in aqueous solution and 3.69 × 10−7 mol/L in plasma solution. Moreover, an artificial light-harvesting system based on this assembly was proposed, benefiting from its good luminescent performance. Nile red (NiR) functioned as an acceptor loaded into assembly, and a highly efficient energy transfer process occurred from PDI-nm/ns-Q[10] to NiR, with an efficiency up to 87 %.

Supramolecular confinement effect enabling light-harvesting system for photocatalytic α-oxyamination reaction

The supramolecular Förster resonance energy transfer (FRET) is seen as a promising approach for organic photocatalysis using dyes as catalysts, because it combines the high efficiency of energy transfer with the dynamic responsiveness based on non-covalent interactions. Here we propose a supramolecular FRET photocatalysis strategy for α-oxyamination reaction based on supramolecular confinement effect. The well-designed benzothiadiazole-based cationic monomer as energy donor and the dyes of Nile Red as acceptor are doped into the amphiphilic surfactants of sodium dodecyl sulfate (SDS). Benefitting from the supramolecular confinement space provided by SDS in aqueous environment, the FRET process between the monomer and Nile Red is effectively achieved (exciton migration rate: 3.99 × 1014 L mol‒1 s‒1). On this basis, the supramolecular FRET system is used as an efficient energy source to catalyze α-oxyamination reactions between a series of 1,3-dicarbonyl compounds and 2,2,6,6-tetramethylpiperidine-1-oxyl under white LED light, showing a yield as high as 94 % and a turnover frequency value of 3.92 h‒1. This photocatalytic result shows a great enhancement compared to that of Nile Red alone.