Search Results (503)

Although amorphous calcium phosphate (ACP) has been extensively employed as a biomaterial in dental and orthopedic fields, its exploration for environmental applications—particularly in potentially toxic element remediation—remains notably limited in the scientific literature. This study reports the rational design of a multifunctional adsorbent by integrating sodium citrate-stabilized ACP (Cit-ACP) nanoparticles into calcium-crosslinked sodium alginate (SA) hydrogel beads for selective Cu²⁺ sequestration from aqueous systems. Comprehensive sorption assessments revealed that equilibrium uptake aligned with the Freundlich isotherm (indicating heterogeneous surface interactions), while kinetic profiles adhered to pseudo-second-order behavior, characteristic of chemisorption-driven processes. Under optimized operational parameters (pH 5.0, 45 °C), the Cit-ACP/SA composite attained an exceptional maximum adsorption amount of 307.76 mg/g. Thermodynamic analysis further confirmed the spontaneity (ΔG° < 0) and endothermic nature (ΔH° > 0) of the process. Multi-technique characterization (XPS, FTIR, XRD, pH trajectory) elucidated a dual-mode adsorption mechanism: (i) ion exchange between aqueous Cu²⁺ and structural Ca²⁺ within both the alginate matrix and ACP framework; and (ii) in situ surface precipitation yielding copper-substituted hydroxyapatite. Owing to its facile aqueous-phase synthesis, superior adsorption performance, biodegradability, macroscopic bead morphology enabling rapid separation, and robust selectivity in complex matrices, the Cit-ACP/SA composite presents a sustainable, scalable, and eco-compatible platform for practical remediation of copper-contaminated wastewater. Full article

Moxifloxacin-based Schiff-base ligands provide a useful platform for tuning the coordination and biological properties of fluoroquinolone derivatives. Here, a moxifloxacin–salicylaldehyde hydrazone ligand (MOX-S) was prepared and coordinated with cobalt(II), nickel(II), copper(II), oxovanadium(IV), and gadolinium(III) ions to obtain a series of metal complexes. Citrate-stabilized gold nanoparticles (AuNPs) were also prepared and functionalized with MOX-S and the Cu(II) complex to evaluate the effect of nanoformulation on biological performance. The compounds were characterized using complementary analytical, spectroscopic, magnetic, thermal, and microscopic techniques. The combined data support 1:2 metal-to-ligand formulations for the complexes and indicate coordination mainly through the azomethine nitrogen and oxygen donor sites of MOX-S. In antimicrobial screening, the activity was strongly metal- and organism-dependent. Cu–MOX-S and VO–MOX-S showed the most pronounced activity against Gram-positive bacteria, with inhibition zones of up to 30 mm, while Cu–MOX-S displayed MIC values of 19.53 and 39.06 µg mL⁻¹ against Bacillus subtilis and Staphylococcus aureus, respectively. Cytotoxicity assays showed that MOX-S was more active than moxifloxacin against MCF-7 and HepG2 cells, while Cu–MOX-S showed enhanced potency, particularly toward HepG2 cells, with an IC₅₀ of 0.98 µM and a selectivity index of 5.97. AuNP formulations further increased the apparent antiproliferative potency in the tested cancer cell lines, giving sub-micromolar IC₅₀ values. Computational analyses, including DFT-based electronic descriptors and molecular docking, provided qualitative support for the experimentally observed coordination and cytotoxicity trends. Overall, metal coordination and AuNP formulations provide complementary strategies for modulating the physicochemical and in vitro biological behavior of this moxifloxacin-derived hydrazone scaffold. Full article

Copper is an indispensable trace element for maintaining metabolic homeostasis; however, the dysregulation and subsequent accumulation of Cu²⁺ are critically linked to neurodegenerative pathologies, including Alzheimer’s disease in humans. Consequently, the development of robust analytical tools for Cu²⁺ monitoring is of paramount importance. Here, we report a 2,2′-dipicolylamine porphyrin (DPAP)-based fluorescent sensor designed for the precise detection of metal cations. Photophysical investigations reveal that DPAP operates via a rapid turn-off fluorescence mechanism, achieving high-performance sensing in the parts-per-million range. Notably, the probe demonstrates exceptional sensitivity with detection limits of 26.3 nM for Cu²⁺ and 34.8 nM for Ni²⁺. Interference studies demonstrated the selectivity of DPAP for Cu²⁺ over a diverse range of competing metal ions such as Na⁺, Ag⁺, Ni²⁺, Cr³⁺, Pb²⁺, Al³⁺, Fe²⁺, Cd²⁺, and Zn²⁺. These results indicate that DPAP is a sensitive and selective probe suitable for copper ion detection. Full article

Chitosan-based copper composites have attracted considerable interest for biomedical and antimicrobial uses due to their biocompatibility, adjustable dielectric characteristics, and ion-mediated antimicrobial effectiveness. In this study, chitosan films doped with Cu(NO₃)₂, containing 3, 6, and 9 wt% of copper nitrate were produced using a solution-casting method at room temperature. This was done to explore the relationship between structural interactions, dielectric relaxation, optical properties, and antimicrobial efficacy. The resulting composite has been investigated physically using FTIR, XRD, optical analysis, and dielectric spectroscopy, and biologically for its antimicrobial activity. FTIR revealed the molecular structure of Cs-Cu(NO₃)₂ and changes resulting from new bond(s) formation and/or decomposition. XRD indicated that there are no peaks assigned for CuO, which weakens the composite antimicrobial activity. Optical analysis showed an increase in the band gap with copper (II) nitrate concentration over 3%. Additionally, the electrical impedance of the resulting composite increased by approximately one decade. A detailed electrical analysis of the charge-carrier types is provided. Moreover, the antimicrobial activity of chitosan is slightly enhanced by the additive copper (II) nitrate in a dose-dependent manner. The current research offers a mechanistic understanding of the structure–property relationships that govern the behavior of Cu(NO₃)₂–chitosan composites, emphasizing the significant influence of processing conditions on adapting of their dielectric and biological properties. Full article

The causative event in transmissible spongiform encephalopathies is the misfolding of the prion protein (PrP), a process influenced, in a way that is not yet fully understood, by transition metal ions, particularly copper, which modulate folding, aggregation, and redox activity. In this study, we investigated the interaction of copper(II) ions with the prion fragment PrP(95–126), which includes the non-octarepeat high-affinity sites His96 and His111, as well as an amyloidogenic tail involved in PrP misfolding and membrane interaction. UV–vis and circular dichroism analyses revealed the predominant formation of a 1:1 Cu/PrP(95–126) complex, accompanied by modest restructuring, consistent with an increased aggregation propensity upon copper binding. The Cu/PrP(95–126) complexes exhibited limited redox activity toward catechol substrates, which was further reduced in membrane-mimetic systems such as SDS micelles and large unilamellar vesicles (LUVs). His96 appears not to play a critical role in copper coordination or redox activation. This study explores the coordination modes and reactivity of copper(II) with PrP, as well as employing a membrane mimic, aspects that are still highly controversial in the literature, providing insights for further in vitro studies. Full article

Sustainable valorization of biomass through hydrothermal carbonization (HTC) represents an environmentally benign method for producing carbon materials for water treatment applications. This research aims to optimize the production of hydrochar from waste food by focusing on parameter optimization, physicochemical characterization, and the capacity of hydrochar to act as an adsorbent for the removal of the copper (II) ion from polluted water. A design of experiments using the RSM approach was employed to evaluate and optimize the influence of carbonization temperature, ranging from 180 to 250 °C, with a residence time of 2–5 h. The predictive ability of the MINITAB-generated model was close to accurate, as demonstrated by the design application for process simulation. The maximum % hydrochar yield was 72.65% for the experimental yield and 71.53% for the predicted yield, both obtained from a sample carbonized at 166 °C for 3.5 h. Batch adsorption experiments were conducted to assess the hydrochar’s ability to remove Cu²⁺ from aqueous solutions, and the Langmuir and the Freundlich isotherms were fitted at different pH levels. A comprehensive characterization of the produced hydrochar was conducted using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM-EDS). The results revealed significant modifications in surface morphology, pore development, and the presence of oxygen-containing functional groups. Based on the findings in this report, it is safe to conclude that hydrochar derived from food waste could serve as a potential adsorbent. Overall, the study demonstrates that sustainable hydrochar production from biomass can simultaneously address waste management challenges and provide an efficient solution for heavy metal removal, thereby advancing circular bioeconomy and environmental protection. Full article

In this study, we present new data about the cytotoxic activity of metal complexes of salinomycin with Co(II), Cu(II) and Zn(II) against human cervical cancer (HeLa) and melanoma (A375, SH-4) cell lines. The effect of the compounds on cell viability and proliferation was evaluated in short-term experiments (up to 72 h) with monolayer cultures using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test, neutral red uptake (NR), crystal violet staining (CV) and double staining with acridine orange (AO) and propidium iodide (PI). The cytotoxic effect of the metal complexes of salinomycin was found to be comparable and even superior to that of the commercial antitumor agents cisplatin and oxaliplatin. Long-term experiments revealed the ability of the compounds to completely suppress 3D cell growth when applied at concentrations ≥ 3.1 μM (for HeLa cells) and ≥6.2 µM (for A375 cells). Embryonic Lep-3 cells are highly sensitive to the influence of the complexes investigated, whereas non-tumor HaCaT human keratinocytes exhibit relatively higher resistance to their cytotoxic effect compared to tumor cell lines. The Zn(II) disalinomycinate exerted the highest selectivity index among the tested compounds against melanoma cells, whereas the non-coordinated antibiotic showed pronounced selectivity toward HeLa cells. Full article

Coumarins represent a distinctive class of non-classical carbonic anhydrase inhibitors that interact with the entrance region of the catalytic pocket rather than directly coordinating the catalytic Zn²⁺ ion. In this study, a series of glycosylated coumarins was synthesized through a copper-catalyzed multicomponent reaction involving propargyl glycosides, salicylaldehyde, and tosyl azide, providing efficient access to iminocoumarin-based glycosides derived from natural carbohydrates. The inhibitory activity of the synthesized compounds was evaluated against human carbonic anhydrase isoforms I, II, IX, and XII using a stopped-flow CO₂ hydrase assay. The compounds showed negligible inhibition of the cytosolic isoforms hCA I and hCA II, while displaying moderate activity toward the tumor-associated isoforms hCA IX and hCA XII, with Ki values ranging from 12.9 to 41.8 μM. Among the series, 6-O-(2H-chromene-2-one-3-yl-methyl)-D-galactopyranose (10a) emerged as the most potent inhibitor of hCA IX and XII. Structure–activity relationship analysis indicated that deprotected glycosyl derivatives exhibit improved inhibitory activity compared to protected analogues. To rationalize these observations, molecular docking followed by molecular dynamics simulations and MM-GBSA binding free energy calculations were performed for both anomeric forms of compound 10a. The computational results revealed a clear preference for the β-anomer, particularly in hCA IX and XII, where favorable interactions with catalytic threonine residues and isoform-specific aromatic residues stabilize the ligand within the active-site entrance. These findings provide a molecular explanation for the experimentally observed selectivity and highlight glycosyl coumarins as potential starting points for further optimization toward selective inhibitors of tumor-associated carbonic anhydrases. Full article

Chitosan, owing to its abundant amino and hydroxyl functional groups, serves as an effective biosorbent for the removal of toxic metal(loid) ions from water. This review summarizes recent advances in chitosan-based adsorbents specifically for arsenate (As(V)) and copper ions (Cu(II)), with an emphasis on adsorption mechanisms and electrospun nanofiber technologies. A conceptual “charge adaptation–structure synergy” model is proposed to elucidate the distinct adsorption behaviors of chitosan toward anionic and cationic substances: under acidic conditions, As(V) adsorption is dominated by electrostatic attraction to protonated amino groups, whereas at pH values near or above the pKa, Cu(II) removal proceeds via synergistic chelation involving deprotonated amino and hydroxyl groups. Competitive and synergistic interactions in binary systems, particularly between As(V) and coexisting anions such as phosphate, are also discussed. Notably, the kinetic advantages of electrospun chitosan nanofibers are highlighted, with equilibrium times shortened from several hours to approximately 0.5–2.6 h. Key challenges and future research directions are further discussed, including scalable manufacturing and the treatment of complex wastewater matrices. Full article

The spontaneous reduction of one Cu(II) center to Cu(I) in a series of three dinuclear copper complexes in acetonitrile is described. These complexes feature ligands that include nitrogen donors from a diazecine ring and imidazole, designated as promeim, thiopromeim, and thioenmeim; the latter two incorporate a thioether as a third donor component. The mechanism of metal reduction was elucidated through spectroscopic and spectrometric techniques (UV-vis, EPR, XANES, ESI-MS) and electrochemical tools, in combination with DFT electronic structure calculations. Based on these and on spectroelectrochemical results, a mechanism is proposed in which the one-electron reduction of one of the copper ions is achieved by a one-electron oxidation in the adjacent imidazole group, while the other copper ion remains as Cu(II). The persistent detection of superoxide and peroxide over long periods suggests a mechanism in which a catalytic cycle involving electron transfer occurs between copper, ligand, and dioxygen. Full article

Ion-imprinting technology based on biosorbents via sorption demonstrates potential for the selective removal of metal ions from water and wastewater. This offers both high sorption capacity and selectivity for specific metals. Current research trends are toward the development of sorbents with minimal environmental impact. Among the most rapidly evolving classes of sorbents are those derived from biopolymers, such as chitosan—a natural derivative of chitin that can be readily functionalized. Due to the growing interest in this topic, it is necessary to summarize the current knowledge. In this article, we provide a comprehensive overview of the latest advances in ion-imprinted chitosan-based materials designed for the purification of metal-contaminated aqueous systems. We conduct a bibliographic analysis and describe a variety of chitosan-based materials exhibiting selectivity toward heavy metals, including chromium Cr(III/VI), cobalt Co(II), nickel Ni(II), copper Cu(II), zinc Zn(II), arsenic As(III/V), cadmium Cd(II), mercury Hg(II), and lead Pb(II). Finally, we discuss future prospects and highlight current research gaps, aiming to guide further scientific exploration and innovation in this promising field. Full article

This study presents a quantitative investigation of substituent effects on the stability of 1:2 complexes formed between para-substituted 2-phenylbenzimidazole ligands and Cu(II) or Co(II) ions. The ligands, featuring hydroxyl (–OH), chloro (–Cl), and nitro (–NO₂) substituents, were synthesized via copper acetate-mediated oxidative cyclization. Stability constants (log K) were determined spectrophotometrically using both the Benesi–Hildebrand and Job methods, which yielded perfectly consistent results and confirmed ML₂ stoichiometry. For both metal series, the stability decreases in the order –OH > –Cl > –NO₂. Excellent linear correlations were obtained between log K and Hammett σ constants, yielding reaction constants of ρ = −0.79 for Cu(II) and ρ = −1.00 for Co(II). These negative ρ values confirm that electron-donating substituents enhance complex stability by increasing electron density on the donor nitrogen. Furthermore, the stability constants for Cu(II) complexes are approximately two orders of magnitude higher than those for Co(II), in agreement with the Irving–Williams series. This work establishes a clear, predictive structure–stability relationship and validates the combined methodological approach for quantifying metal–ligand interactions in tunable benzimidazole systems. Full article

Excessive accumulation of copper ions (Cu²⁺) in the environment and biological systems poses severe risks to ecological balance and human health, necessitating accurate detection and monitoring of Cu²⁺. Schiff base derivatives with favorable optical properties provide an efficient strategy for copper ion recognition. In this paper, fluorescent probe L (5-methyl-2-hydroxybenzaldehyde-(7-diethylaminocoumarin-3-formyl) hydrazone) was synthesized through a three-step reaction using 4-diethylaminosalicylaldehyde and diethyl malonate as starting materials. The structure of probe L was confirmed by melting point analysis, infrared spectroscopy, and nuclear magnetic resonance. Single-crystal X-ray analysis revealed that probe L crystallized into a triclinic lattice with space group $P_1^{-}$. Optical investigations, including UV–Vis spectroscopy, fluorescence spectroscopy, and aggregation-induced emission studies, demonstrated highly sensitive and selective fluorescence “turn-off” behavior of probe L towards Cu²⁺ ions in DMSO, with negligible interference from other metal ions. Job’s plot and crystallographic analysis revealed a 1:1 binding stoichiometry between probe L and Cu²⁺, forming the complex [Cu(L)]. Fluorescence titration experiments revealed a binding constant (K_b) of 5.2 × 10⁶ L/mol and a detection limit of 7.8 × 10⁻⁷ mol/L, indicating excellent sensitivity. These results suggest that probe L has considerable promise for Cu²⁺ detection in aqueous environments, with potential applications in environmental monitoring and public health protection. Full article

Carnosine (or β-alanyl-L-histidine) is an endogenous compound playing very important roles in human organisms as antiglycation and antioxidant agents, and, in addition, helping to mitigate illnesses such as cancer and neurodegenerative diseases. Aiming to explore the chelating ability of carnosine, based on its coordinating possibilities, we started to investigate the metal complexes of essential copper(II), zinc(II), and iron(II) ions coordinated to this dipeptide. Different compounds were isolated in the solid state by adding stoichiometric amounts of metal salts to carnosine at controlled pH or under a controlled atmosphere, with the formation of mono-, bi- and polynuclear species. These complexes were subsequently characterized mainly by spectroscopic techniques (UV–Vis, IR, EPR), in addition to elemental analysis. A binuclear species was isolated with copper(II) and had its structure determined by X-ray diffraction, improving previously reported data in the literature. Two insoluble correlated trinuclear species were isolated with zinc(II) ions, using perchlorate or chloride as counter-ions. In the case of iron, a mononuclear species was verified with Fe(II) ions, obtained under an inert atmosphere. Further, the antioxidant properties of free carnosine and the copper–carnosine complex were verified by their scavenging activity toward the ABTS^•+ radical, using Trolox as a reference, showing significant activity. The carnosine–metal complexes were also tested as potential antineoplastic agents, in comparison to the free ligand, after 24 h of incubation at 37 °C, using malignant HeLa, SKMEL 28 and SKMEL 147, and non-tumor fibroblast cells. Results indicated neglected or poor anti-proliferative properties of these metal complexes, when compared to other similar compounds described in the literature. Full article

This study investigates the potential of Quercus robur leaves as a bio-coagulant for the removal of heavy metal ions, including zinc (II), iron (III), copper (II), and chromium (VI), from water. The Quercus robur leaves were used in two forms: Quercus robur powder (QRP) and Quercus robur extract (QRE). The extract was prepared using distilled water to extract the active compounds responsible for coagulation, such as proteins, polysaccharides, and total phenolics. The QRP was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and zeta potential analysis to identify the active functional groups, surface morphology, crystallinity, and surface charge, all of which are key factors influencing its performance in the coagulation–flocculation process. In this work, the Response Surface Methodology (RSM)-based Central Composite Design (CCD), with two factors (bio-coagulant dosage and initial metal concentration), was used examine the effects of each factor and their interaction, while the responses were zinc (II) removal, iron (III) removal, copper (II) removal, and chromium (VI). The results revealed high removal efficiency for these metal ions, reaching up to 100% for all metal ions treated with QRP and QRE. The quality of the model predictions was evaluated using analysis of variance (ANOVA). For all metal ions, the R² (≥97%), R² adjusted (≥95%), and p-values (<0.05), indicating an excellent model accuracy. These results show that bio-coagulants (QRP and QRE) based a Quercus robur leaves are a promising, effective, and reliable option for removing heavy metal ions from water, and that the models developed can be used to optimize the coagulation-flocculation process. Full article