Search Results (569)

Application of organic ligand 2-(3-ethyl-pyrazin-2-yl)quinoline-4-carboxylate with N/O donor atoms enabled solvothermal synthesis of a 2D Cu(II) coordination polymer, {Cu(L)BF₄}_n (L = deprotonated 2-(3-ethyl-pyrazin-2-yl)quinoline-4-carboxylate). Both the ligand and its coordination polymer have been characterized. The condensed ring system of the applied ligand promotes the formation of coordination polymers rather than mononuclear species. The obtained 2D coordination polymer is photoluminescent with bathochromic/hypsochromic shifts in ligand absorption bands leading to a single absorption band at 465 nm. Density Functional Theory was employed to provide a theoretical description of the possible conformational changes within the ligand, with emphasis on the difference between the ligand conformation in its hydrochloride salt and in the polymer. Two models of polymer fragments were constructed to describe the electronic structure and non-covalent interactions. The Quantum Theory of Atoms in Molecules (QTAIM) was applied for this purpose. Using the obtained results, we were able to develop potential energy profiles for various conformations of the ligand. For the set of the studied systems, we detected non-covalent interactions, which are responsible for the spatial conformation. Concerning the models of polymers, electron spin density distribution has been visualized and discussed. Full article

Candida albicans is a clinically important fungal pathogen capable of causing both superficial and systemic infections, particularly in immunocompromised individuals. A key factor contributing to its pathogenicity is its ability to form biofilms, structured microbial communities that confer significant resistance to conventional antifungal therapies. Addressing this challenge, we explored the antivirulence potential of acridine derivatives, a class of heterocyclic aromatic compounds known for their diverse biological activities, including antimicrobial, antitumor, and antiparasitic properties. In this study, a series of acridine derivatives was screened against C. albicans biofilms, revealing notable inhibitory activity and highlighting their potential as scaffolds for the development of novel antifungal agents. Among the tested compounds, acridine-4-carboxylic acid demonstrated the most promising activity, significantly inhibiting the biofilm formation at 10 µg/mL without affecting planktonic cell growth, and with a minimum inhibitory concentration (MIC) of 60 µg/mL. Furthermore, it attenuated filamentation and cell aggregation in a fluconazole-resistant C. albicans strain. Toxicity assessments using Caenorhabditis elegans and plant models supported its low-toxicity profile. These findings highlight the potential of acridine-based scaffolds, particularly acridine-4-carboxylic acid, as lead structures for the development of therapeutics targeting both fungal growth and biofilm formation in Candida albicans infections. Full article

The combined effect of temperature-adapted inocula and anaerobic fermentation (AF) settings (pH 5.1 and 50 °C) were assessed to produce short-chain carboxylates (SCCs). In this study, the AF of carrot pulp was investigated using inocula adapted at different temperatures (25, 35, and 55 °C) with the aim of shifting the microbiome activity from biogas to SCC production. The highest SCC content (17.2 g COD L⁻¹), and bioconversion (26.1%) and acidification efficiency (56.3%) were achieved with 35 °C-adapted inoculum. Lactic acid production prevailed in all reactors, demonstrating a high selectivity in SCC production. Both the microbial richness and diversity sharply diminished in the 35 °C and 55 °C operated reactors, with Firmicutes phylum identified as key players of the lactic acid production in AF. The results demonstrated that the operating temperature played a key role in shaping the microbial structure of inocula, leading to different process performances and highlighting thermophilic AF as a feasible process to produce lactic acid. Full article

In this study, we comprehensively compare electrical conduction behavior under an applied electric field and electrical conductivity variation with temperature in low-density polyethylene (LDPE)/CNT composites with different dispersions and covalent functionalizations. Composites with different dispersions were prepared using solution and melt mixing processes. The solution-mixed composites exhibited better dispersion and higher electrical conductivity compared to the melt-mixed composites. At a high critical content (beyond the percolation threshold), the current–voltage (I–V) curve of the solution-mixed composites exhibited linear conduction behavior due to the formation of a continuous conductive network. In contrast, the melt-mixed composites exhibited nonlinear conduction behavior, with the conductive mechanism attributed to the field emission effect caused by poor interfacial contact between the CNTs. Additionally, LDPE/CNT-carboxyl (LDPE/CNT-COOH) and LDPE/CNT-hydroxy (LDPE/CNT-OH) composites demonstrated better dispersion but displayed lower electrical conductivity and similar nonlinear conduction behavior when compared to unmodified ones. This is attributed to the surface defects caused by the modification process, which lead to an increased energy barrier and a decreased transition frequency in the field emission effect. Furthermore, the temperature-dependent electrical conductivity results indicate that the variation trend in current with temperature differed among LDPE/CNT composites with different dispersions and covalent functionalizations. These differences were mainly influenced by the gap width between CNTs (mainly affected by dispersion and aspect ratio of CNTs), as well as the electrical conductivity of CNTs (mainly influenced by surface modification and intrinsic electrical conductivity of CNTs). Full article

This study investigates the combined use of electron beam irradiation (EBI) and nanotechnology to develop improved food packaging films. EBI, commonly applied for sterilization, can alter polymer microstructure, while irradiated cellulose nanocrystals (CNCs) offer enhanced functionality when incorporated into biopolymer matrices. Here, CNCs were irradiated with doses up to 50 kGy, leading to the formation of carboxyl and aldehyde groups, confirmed by FTIR analysis, as a consequence of the initial formation of free radicals and peroxides that may subsist in that original form or be converted into various carbonyl groups. Flexible films were obtained by incorporating pristine and EB-irradiated CNCs in an internal mixer, using minute amounts of poly(ethylene oxide) (PEO) to facilitate the dispersion of the filler within the polymer matrix. The resulting PLA/PEO/CNC films were evaluated for their mechanical, thermal, barrier, and antioxidant properties. The results showed that structural modifications of CNCs led to significant enhancements in the performance of the composite films, including a 30% improvement in water barrier properties and a 50% increase in antioxidant activity. These findings underscore the potential of irradiated CNCs as effective additives in biopolymer-based active packaging, offering a sustainable approach to reduce dependence on synthetic preservatives and potentially extend the shelf life of food products. Full article

Ophiocordyceps sinensis, is an entomopathogenic fungus renowned for its medicinal properties, thriving in the frigid and high-altitude regions of the Qinghai–Tibet plateau. Given the limited availability of wild resources and the increasing recognition of their medicinal value, the cultivation of O. sinensis was initiated. However, there is a paucity of research investigating the disparities in their quality. This study evaluated the primary physiological indicators of both wild and cultivated O. sinensis. It also employed proteome and untargeted metabolome approaches to elucidate the differences in quality and underlying mechanisms between the two types. The results revealed that the contents of key representative components, including polysaccharide, crude protein, adenosine, and mannitol, were higher in wild O. sinensis than in cultivated O. sinensis. A total of 499 differentially expressed proteins (DEPs), including 117 up-regulated and 382 down-regulated DEPs, were identified in wild and cultivated O. sinensis. Additionally, 369 up-regulated differentially accumulated metabolites (DAMs) and 737 down-regulated DAMs were also identified. Wild O. sinensis had higher relative levels of lysophospholipid metabolites, while cultivated O. sinensis had higher relative levels of aldehydes and carboxylic acids. Correlation analysis revealed that different habitats altered 47 pathways shared between the proteome and metabolome, including carbohydrate metabolism and energy metabolism. β-glucosidase and α-galactosidase play essential roles in carbohydrate catabolism and may indirectly influence amino acid synthesis through energy metabolic pathways. The differential expression of polyamine oxidase (PAO) could reflect variations in polyamine metabolism and ammonia production between wild and cultivated O. sinensis. These variations may consequently affect nitrogen homeostasis and the biosynthesis of nitrogen-containing compounds, ultimately leading to differences in nutritional quality. In conclusion, these findings offer a novel perspective on the applications of O. sinensis and serve as a reference for the targeted development of cultivated O. sinensis. Full article

Olfaction has been extensively studied in the yellow fever mosquito, Aedes aegypti. This species uses its sense of smell to find blood hosts and other resources, contributing to its impact as a vector for human pathogens. Two major families of protein-coding genes, the odorant receptors (Ors) and the ionotropic receptors (Irs), provide the mosquito with sensitivities to distinct classes of volatile compounds in the antennae. Individual tuning receptors in both families require co-receptors for functionality: Orco for all Ors, and Ir8a for many Irs, especially ones that are involved in carboxylic acid detection. In Drosophila melanogaster, disruptions of Orco or Ir8a impair receptor function, tuning receptor expression, and membrane localization, leading to general anosmia. We reasoned that Orco and Ir8a might also be important for coordinated chemosensory receptor expression in the antennal sensory neurons of Ae. aegypti. To test this, we performed RNAseq and differential expression analysis in wildtype versus Orco^−/− and Ir8a^−/− mutant adult female antennae. Our analyses revealed Or and Ir tuning receptors are broadly under-expressed in Orco^−/− mutants, while a subset of tuning Irs are under-expressed in Ir8a mutants. Other chemosensory and non-chemosensory genes are also dysregulated in these mutants. Furthermore, we identify differentially expressed transcription factors including homologs of the Drosophila melanogaster Mip120 gene. These data suggest a previously unknown pleiotropic role for the Orco and Ir8a co-receptors in the coordination of expression of chemosensory receptors within the antennae of Ae. aegypti by participating in a feedback loop involving amos and members of the MMB/dREAM complex. Full article

Global warming poses a significant threat to lake ecosystems, with high-mountain lakes being among the earliest and most severely impacted. However, the processes affecting water ecology under climate change remain poorly understood. This study investigates, for the first time, the effects of regional warming on three high-mountain lakes, Sulzata, Okoto and Bubreka, located in the Rila Mountains, Bulgaria, by examining shifts in bacterial metabolic capacity in relation to the rate and range of utilizable carbon sources using the Biolog EcoPlate™ assay. Over the last decade, ice-free water temperatures in the lakes have risen by an average of 2.6 °C, leading to increased nutrient concentrations and enhanced primary productivity, particularly in the shallowest lake. Bacterial communities responded to these changes by increasing their metabolic rates and shifting substrate preferences from carbohydrates to carboxylic acids. While the utilization rates of some carbon sources remained stable, others showed significant changes—some increased (e.g., D-galactonic acid γ-lactone and itaconic acid), while others decreased (e.g., α-D-lactose and D-xylose). The most pronounced effects of warming were observed in June, coinciding with the onset of the growing season. These findings suggest that rising temperatures may substantially alter bacterial metabolic potential, contributing to a long-term positive feedback loop between lake nutrient cycling and climate change. Full article

A dysprosium-based metal–organic framework (MOF), namely [DyLH₂O]_n (1) (H₃L = 4-((bis(carboxymethyl) amino)methyl)benzoic acid), was successfully synthesized via the hydrothermal method. According to the structural characterization, metal centers in this complex are linked by four bridges (two oxygens and two carboxylic groups), leading to Dy₂ units. On further connection by single carboxylic groups, the dimeric units extend to form a two-dimensional layer with a 4⁴ topological structure. Finally, the 2D layers were assembled into a 3D framework by the L⁻³ anions. A thermogravimetric test shows that [DyLH₂O]_n can maintain high thermal stability after losing water, until the temperature reaches 426 °C. Magnetic studies on 1 reveal antiferromagnetic exchange interactions of Dy³⁺…Dy³⁺ at low temperatures. Additionally, frequency-dependent out-of-phase signals were observed in alternating current (ac) magnetic susceptibility measurements for 1, indicating that it has slow magnetic relaxation features. Full article

Biosurfactants have emerged as promising agents for environmental remediation due to their ability to complex, chelate, and remove heavy metals from contaminated environments. This review evaluates their potential for recovering critical minerals from waste materials to support renewable energy production, emphasizing the role of biosurfactant–metal interactions in advancing green recovery technologies and enhancing resource circularity. Among biosurfactants, rhamnolipids demonstrate a high affinity for metals such as lead, cadmium, and copper due to their strong stability constants and functional groups like carboxylates, with recovery efficiencies exceeding 75% under optimized conditions. Analytical techniques, including Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Fourier-Transform Infrared spectroscopy (FTIR), and Scanning Electron Microscopy (SEM), are instrumental in assessing recovery efficiency and interaction mechanisms. The review introduces a Green Chemistry Metrics Framework for evaluating biosurfactant-based recovery processes, revealing 70–85% lower Environmental Factors compared to conventional methods. Significant research gaps exist in applying biosurfactants for extraction of metals like lithium and cobalt from batteries and other waste materials. Advancing biosurfactant-based technologies hold promise for efficient, sustainable metal recovery and resource circularity, addressing both resource scarcity and environmental protection challenges simultaneously. Full article

This study investigates the degradation mechanisms of fiber-reinforced polymer (FRP) matrices in composite insulators under partial discharge (PD) conditions. The degradation products may further cause deterioration of the electrical and chemical resistance (ECR) glass fibers. Using pyrolysis–gas chromatography-mass spectrometry (PY-GC-MS) and high-performance liquid chromatography–tandem mass spectrometry (HPLC-MS-MS), the thermal degradation gas and liquid products of the degraded FRP matrix were analyzed, revealing the presence of organic acids. These acids form when the epoxy resin’s cross-linked bonds break at high temperatures, generating anhydrides that hydrolyze into carboxylic acids in the presence of moisture. The hydrolyzation process is accelerated by hydroxyl radicals produced during PD. The resulting carboxylic acids deteriorate the glass fibers within the FRP matrix by degrading surface coupling agents and reacting with the alkali metal–silica network, leading to the substitution and precipitation of metal ions. Organic acids, particularly carboxylic acids, were found to have a more severe deteriorating effect on glass fibers compared to inorganic acids, with high temperatures exacerbating this process. These findings provide critical insights into the deterioration mechanisms of FRP under operational conditions, offering valuable guidance for optimizing manufacturing processes and enhancing the longevity of composite insulators. Full article

For the interaction of angiotensin II (AngII) with AngII type 1 receptors (AT₁R), two potential proton hopping pathways have been identified, each associated with distinct physiological outcomes. The octapeptide AngII (Asp¹-Arg²-Val³-Tyr⁴-Ile⁵-His⁶-Pro⁷-Phe⁸) appears to form a charge relay system (CRS) in solution in which the C-terminal carboxylate abstracts a proton from the His⁶ imidazole group, which, in turn, abstracts a proton from the Tyr⁴ hydroxyl (OH) group, creating a tyrosinate anion. When AngII binds to the AT₁R, the CRS can be reconstituted with D281 of the receptor taking up the role of the Phe⁸ carboxylate in the tripartite interaction, whilst the Phe⁸ carboxylate forms a salt bridge with K199 of the receptor. As a consequence, the Tyr⁴ OH of AngII is positioned with accessibility to either the Phe⁸ carboxylate (bound to K199) or the His⁶ imidazole (activated by D281), thereby creating a potential gating mechanism for AT₁R receptor signaling. This study summarizes evidence based on structure activity data for various analogs wherein Tyr⁴ OH interaction with His⁶ imidazole (CRS formation) leads to G protein sequestration and vasoconstriction, whereas Tyr⁴ OH interaction with Phe⁸ carboxylate (bound to K199) engenders arrestin-mediated vasodilation and receptor desensitization. These findings, combined with quantum mechanical (semiempirical) calculations of CRS proton transfer presented herein, provide insights for the therapeutic targeting of angiotensin receptor blockers (sartans) and the development of second-generation drugs (bisartans). Full article

Current hydrogels used for cartilage tissue engineering often lack the mechanical strength and structural integrity required to mimic native human cartilage. This study addresses this limitation by developing reinforced hydrogels based on a ternary polymer blend of poly(vinyl) alcohol (PVA), gelatin (GL), and chitosan (CH), with gentamicin sulfate (GS) as an antimicrobial agent and a crosslinker. The hydrogels were produced using two crosslinking methods, the freeze/thaw and heated cycles, and reinforced with forcespun polycaprolactone (PCL) nanofiber to improve mechanical performance. Chemical characterization revealed that GS forms weak hydrogen bonds with the ternary polymers, leading to esterification with PVA, and covalent bonds are formed as the result of the free amino group (-NH₂) of chitosan that reacts with the carboxylic acid group (-COOH) of gelatin. SEM images help us to see how the hydrogels are reinforced with polycaprolactone (PCL) fibers produced via force spinning technology, while mechanical properties were evaluated via uniaxial tensile and compressive tests. Water retention measurements were performed to examine the crosslinking process’s influence on the hydrogel’s water retention, while the hydrogel surface roughness was obtained via confocal microscopy images. A constitutive model based on non-Gaussian strain energy density was introduced to predict experimental mechanical behavior data of the hydrogel, considering a non-monotonous softening function. Loading and unloading tests demonstrated that GS enhanced crosslinking without compromising water retention or biocompatibility because of the reaction between the free amino group of CH and the carboxylic group of gelatin. The PCL-reinforced PVA/GL/CH hydrogel shows strong potential for cartilage repair and tissue engineering applications. Full article

Cancer remains a leading global cause of mortality, highlighting the critical need for effective early diagnosis. Despite advancements in treatment, early detection and imaging continue to pose significant challenges. Functionalized carbon nanotubes (CNTs) have emerged as promising nanomaterials due to their unique structural properties and versatile functionalization strategies. This review explores the role of both covalent (e.g., fluorination, hydrogenation, cycloadditions, aryldiazonium salt reduction, organometallic ion attachment, carboxylation, amidation, esterification, and metallic nanoparticle attachments) and non-covalent functionalization methods (e.g., surfactant coating, polymer wrapping, biomolecule attachment, and polymer encapsulation) in enhancing CNT biocompatibility and diagnostic efficiency. Functionalized CNTs are extensively applied in cancer detection through highly sensitive biosensors, including electrochemical, optical, and field-effect transistor-based systems, capable of detecting various cancer biomarkers with exceptional sensitivity. Additionally, they offer significant advantages in cancer imaging modalities such as fluorescence imaging, magnetic resonance imaging (MRI), computed tomography (CT), and ultrasound imaging, improving contrast, resolution, and specificity. This review also discusses the challenges and future directions in the development of CNT-based diagnostic platforms, emphasizing the need for continued research to advance their clinical translation and integration into routine cancer diagnostics. Full article

We developed a novel biodegradable poly(lactic-co-glycolic acid) (PLGA) polymer chemically modified with paclitaxel (PTX) to form a PLGA-PTX hybrid. Pre-modification of PTX enhanced its loading in PLGA-PTX nanoparticles (NPs). Background/Objectives: PTX is one of the most effective chemotherapy agents used in cancer therapy. The primary mode of PTX’s action is the hyperstabilization of microtubules leading to cell growth arrest. Although highly potent, the drug is water insoluble and requires the Cremophor EL excipient. The toxic effects of the free drug (e.g., neurotoxicity) as well as its solubilizing agent are well established. Thus, there is strong clinical rationale and need for exploring alternative PTX delivery approaches, retaining biological activity and minimizing systemic effects. Methods: The PTX modification method features reacting the C-2′ and C-7 residues with a linker (succinic anhydride) to produce easily accessible carboxyl groups on the PTX for enhanced coupling to the hydroxyl group of PLGA. The PLGA-PTX hybrid, formed via esterification reaction, was used to formulate lipid-coated PLGA-PTX NPs. As proof of concept, the PLGA-PTX NPs were tested in ovarian cancer (OvCA) models, including several patient-derived cell lines (PDCLs), one of which was generated from a platinum-resistant patient. Results: The PLGA-PTX NPs critically remained stable in water and serum while enabling slow drug release. Importantly, PLGA-PTX NPs demonstrated biological activity. Conclusions: We suggest that this approach offers both a new and effective PTX formulation and a possible path towards the development of a new generation of OvCA treatment. Full article