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[Display omitted] The solubilization of sodium diclofenac (Na-DFC) in a glycerol monooleate-based emulsion triggers series of structural changes. Incorporation of Na-DFC, leads to formation of a reverse hexagonal mesophase between 2 and 5 wt% Na-DFC. Between 6 and 9 wt% Na-DFC, the hexagonal symmetry gradually transitions to a disordered lamellar mesophase. These structural shifts impact the system's storage modulus, structuring enthalpy, and structural diffusivity. Despite these transitions, the driving force for Na-DFC release remains consistent, leading to hypothesize that the interfacial structure remains unchanged during Na-DFC release. The nano-structural modifications imposed by the Na-DFC load and release were assessed by small-angle X-ray diffraction (SAXD), spin-probe electron paramagnetic resonance (EPR), and nuclear quadrupole resonance (NQR). The selective solubilization of Na-DFC was demonstrated by SAXD peak fittings, revealing an increase of hexagonally oriented rods at the expense of non-oriented micelles, rather than gradual micellar elongation. Computation of the EPR spectra also showcased the selective solubilization of Na-DFC at an enhanced free energy interface (γ), evidenced by step-wise variations in polarity, microviscosity, and order parameters. Additionally, NQR analysis highlighted a higher anisotropy for sodium compared to deuterium, linking the selective solubilization of Na-DFC to heterogeneous structural transformations. These findings underscore the heterogeneous nature of solubilization-release processes, driven by locally increased micellar free energy. Consequently, the loaded Na-DFC interfaces maintain a constant γ, ensuring a consistent release driving force despite the structural transitions affecting the matrix. The ability to selectively solubilize guest molecules may herald a new era in the utilization of selective molecular interfacial loading. [ABSTRACT FROM AUTHOR]

Polynitroxides with varying numbers of nitroxide groups (one to four) derived from different aromatic core structures show intramolecular electron spin--spin coupling. The scope of this study is to establish an easy methodology for extracting structural, dynamical, and thermodynamical information from the EPR spectra of these polynitroxides which might find use as spin probes in complex systems, such as biological and host/guest systems, and as polarizing agents in dynamic nuclear polarization (DNP) applications. Density functional theory (DFT) calculations at the B3LYP/6-31G(d) level provided information on the structural details such as bond lengths and angles in the gas phase, which were compared with the single crystal X-ray diffraction data in the solid state. Polarizable continuum model (PCM) calculations were performed to account for solvent influences. The electron paramagnetic resonance (EPR) spectra of the polynitroxides in chloroform were analyzed in detail to extract information such as the percentages of different conformers, hyperfine coupling constants a, and rotational correlation times τc. The temperature dependence on the line shape of the EPR spectra gave thermodynamic parameters ΔH and ΔS for the conformational transitions. These parameters were found to depend on the number and relative positions of the nitroxide and other polar groups. [ABSTRACT FROM AUTHOR]

Abstract: Computer aided analysis of electron paramagnetic resonance (EPR) spectra of tetrachloro-dibenzodioxin labelled with a nitroxide radical (TCDD-T) was employed to investigate the adsorption of dioxin vapours onto two carbons, the activated carbon (AC) NORIT GL50 and a carbon directly taken from a waste incinerator (WI) plant, termed EVN.2, and a low-polar micelle-templated mesoporous silica, termed lpMTS. Several experimental conditions were varied to optimize the adsorption process and to mimic dioxin adsorption occurring in a WI plant. Solvent vapours did not perturb dioxin adsorption. EPR analysis suggested that the nitroxide labelled-dioxin interacted (dipole–dipole interactions) with oxygenated groups, mainly C–O–C groups of the carbon and siloxane groups of lpMTS. The kinetics of adsorption was analyzed at different flow rates. The adsorption was large for NORIT and lpMTS already after few seconds, but a complete adsorption was achieved with a slow kinetics, whereas the EVN.2 sample showed a negligible adsorption even after 1min. The results are interpreted in terms of the surface characterization (S BET, pore volume and pore size distribution) of the adsorbents. The EPR method described in this study can provide useful and unique information on the adsorption process of dioxins onto microporous carbons and mesoporous MTSs. Moreover, this method may be applied to different adsorbates and porous adsorbents. [ABSTRACT FROM AUTHOR]

Abstract: The structure of the octadecyl (C18) chain layer attached to a silica surface in the presence of binary solvents (acetonitrile/water; methanol/water) was investigated by electron paramagnetic resonance (EPR) and reverse-phase high-performance liquid chromatography (RP-HPLC), using 4-hydroxy-2,2,6,6 tetramethylpiperidine-N-oxyl (Tempol) to mimic the behavior of pollutants with medium–low polarity. The computer-aided analysis of the EPR spectra provided structural and dynamical information of the probe and its environments which clarified the modifications of the chain conformations that occur at different solvent compositions. Capacity factors, k′, were calculated as a function of the percentage of water/organic solvent (mobile phase), and the retention behavior of the C18-functionalized silica surface (stationary phase) was compared with the results obtained with EPR analysis under static conditions. In particular, EPR analysis showed that, at percentages of ACN equal or higher than 50%, the chain layer assume a quite ordered structure, whereas at percentages lower than 50% the chains tend to collapse and fold on the silica surface. In this latter situation, the hydrophobic net of the C18 chains strongly limits Tempol mobility. In methanol/water mixtures, both EPR and RP-HPLC analysis showed that the probe was adsorbed into a poorly ordered interphase. If the residual silanols at the silica surface were bonded to a sililating agent (endcapping), both EPR and RP-HPLC analysis showed a decreased adsorption of the probe with respect to the non-endcapped silica at the same mobile phase composition. [ABSTRACT FROM AUTHOR]

Abstract: Dendrimers are a new class of nanotechnological polymers suitable for drug targeting, microarray systems or detoxication. The present study is devoted to a detailed analysis of binding between PAMAM dendrimers and bovine serum albumin (fatty acid free or loaded with oleic, linoleic, oleic+linoleic or oleic+linoleic+arachodonic acids) by measuring zeta-potential, fluorescence quenching, fluorescence anisotropy and electron paramagnetic resonance. Addition of PAMAM G2 and G6 dendrimers to protein solutions resulted in attachment to the protein molecule. The PAMAM dendrimers also competed with BSA for fatty acids if two or three fatty acids were loaded per protein. This can lead to the extraction of fatty acids from BSA to the PAMAM dendrimer. [Copyright &y& Elsevier]

Mastic resin used as a covering film for painting protection was analyzed by electron paramagnetic resonance (EPR) spectroscopy, both as received and upon aging in sun-light. The effect of prolonged exposure to sun-light was mimicked by UV and, more so, by xenon lamp irradiation. Solid mastic presented EPR signals due to radicals trapped by PBN in solution. Data in the literature indicated the formation of acyl radicals (RCO·). These radicals preferentially dissolved in medium polarity solvents. The radical concentration in the solid mastic increased over time more than 50 times upon UV irradiation for 96 h and, even more, by xenon irradiation for 800 h. Also the PBN-trapped radicals in solution increased in concentration by irradiation. Small nitroxide radicals (TEMPO) interacted with a polar fraction of mastic dissolved in methanol, but mainly interacted with low polar mastic molecules in hydrophobic solvents. It was suggested, on the basis of both the PBN-spin trapping data and the TEMPO mobility variation in the solvents at different polarities, that terpenoid molecules partially polymerize by a radical mechanism to form low molecular weight products. A polyaromatic-radical (pyrene-TEMPO) and a biomolecule-radical (doxylcholestane) both interact weakly with mastic molecules in cyclohexane solutions. A positively charged surfactant radical (dimethylammonium-TEMPO bromide) was easily adsorbed onto the solid mastic surface suggesting that detergents are responsible for mastic degradation. In conclusion, this study provided information on the degradation mechanism of mastic resin and on its interacting ability towards external molecules and pollutants. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) has been used to investigate the adsorption capability and the surface interacting ability towards Cu(II) solutions (CuCl2, Cu(NO3)2, CuSO4 in water or ethanol) of various carbon blacks, both graphitized and ungraphitized, selected on the basis of the surface area, namely, Carbograph1 (area=100 m2/g), Carbograph4 (area=210 m2/g), and Carbograph5 (area=560 m2/g), which were indicated as C1g, C4g, C5g (g=graphitized), and C1ng, C4ng, C5ng (ng=ungraphitized). The EPR analysis was supported by surface analysis, for evaluating the surface area, the pore volume and the porosity, and by atomic absorption to obtain the adsorbed Cu(II) amounts. Graphitization provokes a decrease in surface area, but C1g, at low surface area, showed a unexpected increase of the adsorption ability ascribed to the formation of new surface porosity closed by graphite layers. The carbon samples showed a broad unresolved EPR signal due to mobile unpaired electrons in the carbon matrix. Graphitized samples presented a narrower signal than ungraphitized samples, which increases in width with the increase in surface area (with the exception of C5ng due to the high exposition of the wide surface to oxydizing external agents) and upon prolonged thermal treatment. The signal intensity of the carbon paramagnetic centers decreases upon Cu(II) adsorption. Computer aided analysis of the EPR spectra of the solids after Cu(II) adsorption allowed to extract structural information on the Cu-surface site complexes. The Cu2+ ions coordinated with surface polar sites, mainly oxygenated. Adsorption depends on the different Cu(II) salts, caused by the salt solubility and the interacting ability of the counter-ion. In several cases the solutions concentrated in the carbon porosity leading to precipitation of the salt. Ethanol solutions are more adsorbed at the carbon surface than water solutions; Cu(II) partially retains its solvation shell and partially presents electron transfer to the carbon surface. Adsorption is favored to ungraphitized carbons with respect to the graphitized ones due to both the higher surface area, and the higher hydrophilicity of the surface. In summary, these carbon powders, widely used for chromatographic applications, show an adsorption capability towards Cu(II) solutions higher than expected due to both a definite porosity, and the presence of polar groups which are not eliminated with chemical surface treatments. [ABSTRACT FROM AUTHOR]

Investigates the structure of Cu(II) complexes formed with anionic starburst dendrimers in aqueous solution. Use of the electron paramagnetic resonance (EPR) technique; Line shapes of the EPR spectra of the complexes; Magnetic parameters; Evaluation of Cu(II) bonding parameters; Covalency of in-plane bonds.

[Display omitted] • New fluorescence PAMAM dendrimer modified with 1,8-naphthalimide. • Photophysical characterisation of dendrimer in different organic solvents. • Synthesis and EPR characterization of metallodendrimer, containing Cu(II). • Microbiological activity of dendrimers against different pathogens. A new fluorescent dendrimer was obtained by modifying the periphery of a PAMAM dendrimer from zero generation. The modification involves substitution at the C-4 position with 1,8-naphthalimide units containing N -methylpiperazine and the addition of Cu(II) ions forming the metallodendrimer [Cu 2 (D)(NO 3) 2. The dendrimer ligand and metallodendrimer were subjected to UV–vis, fluorescence spectroscopy, FT-IR, NMR, and SEM investigations to define their precise structure. The photophysical characteristics of the yellow-green fluorescent dendrimer were studied in organic solvents of different polarity. Results show that polar solvents favour a photoinduced electron transfer (PET) process. Experiments on the effect of pH in an ethanol - water solution (1:4 v/v) revealed the fluorescence of the dendrimer to be more than seventeen times higher than that in an acidic medium. Electron paramagnetic resonance (EPR) studies were performed to characterize the complexing ability of the dendrimer towards Cu(II) by varying the [Cu(II)/dendrimer external sites] molar ratio in DMSO solution. The EPR results suggest that Cu(II) formed a Cu-N2O2 square-planar coordination with nitrogen sites (N-CH 3 sites of 1,8-methylpiperazine, and amine and amide groups) at the dendrimer internal/external interface, and 2 solvent molecules. The Cu(II) complex was characterized by restricted mobility conditions. Copper (II) ions were distributed between the dendrimer interface and the external surface; saturation of the nitrogen sites at the interface occurred at a 1:2 M ratio between Cu(II) and methylpiperazine units. These results are useful in view of the use of this metallodendrimer as anticancer and antimicrobial drugs. The antimicrobial activity of dendrimer ligand and its Cu(II) complex was tested against several model strains bacteria and yeasts in agar, in liquid medium, and after their deposition onto a cotton fabric. The results showed good antibacterial effect of dendrimer ligand, which was enhanced by its Cu(II) complexation. [ABSTRACT FROM AUTHOR]

A series of new organometallic carbosilane dendrimers functionalized with Copper(II) complex on the surface were synthesized and characterized as potential anticancer agents. These metallodendrimers were synthesized through the reaction of dendritic ligands containing N,N- and N,O- donor atoms able to act as chelating agents with CuCl 2 as metallic ion precursor. The structural characterization of these complexes was addressed through the use of different analytical and spectroscopical techniques. Particularly, an electron paramagnetic resonance study was performed to corroborate the coordination properties of these dendritic ligands. A preliminary study was carried out to establish the cytotoxicity of the new synthesized compounds in human prostate (PC3) and human cervical (HeLa) cancer cell lines in order to evaluate their potential as anticancer agents and compare their activity with other copper or analogous ruthenium metallodendrimers. [ABSTRACT FROM AUTHOR]

Abstract: Amphiphilic polymers can be used as tools to manipulate the behavior of reverse microemulsions. EPR spectroscopy employing the spin probe 5-doxyl stearic acid was used to study the adsorption of a comb type polymer (polymaleic anhydride octyl vinyl ether) and a diblock polymer (polybutadiene–ethylene oxide) onto reverse microemulsion droplets formed from Aerosol-OT/heptane/water. The findings indicate that the comb type polymer was adsorbed by the reverse microemulsion drops at low polymer concentrations causing a structural change of the micelle. [Copyright &y& Elsevier]

• Versatile synthesis for imidazolium-terminated carbosilane dendrimers. • EPR study on the generation-dependent interaction of carbosilane dendrimers. • Relationship between the membrane interaction and cytotoxicity on cancer cell lines. • Third generation imidazolium-ended carbosilane dendrimer good anticancer drug. A new family of imidazolium-terminated carbosilane dendrimers and dendrons was synthesized and characterized as a nanotechnological alternative to current therapies. The aim of this research was the study of the interacting process of nano-structures with a cell membrane model (lecithin liposomes), with the final ambitious purpose to use these nano-structures for biomedical applications, e.g. as anticancer drug. The interactions occurring over time between the dendrimers, at different generations (from G1 to G3) and different concentrations (1 mM, 10 mM and 20 mM), and cell membrane models were investigated using a computer-aided analysis of the electron paramagnetic resonance (EPR) spectra of selected spin probes, able to enter the liposome membrane, mimicking the phospholipid behavior. The EPR analysis provided structural and dynamical information on the systems indicating that the increase in generation and concentration produced an increased perturbation of the liposome structure. The dendrons and G1 dendrimers poorly interacted and this interaction was almost independent on dendrimer concentration and decreased over time. Conversely, G3 dendrimers showed a significant variation of the interacting process in respect of concentration. A fast kinetics of internalization was proposed at low dendrimer concentration, while accumulation of dendrimers at the liposome surface slowed down the internalization process. The cytotoxic effect of the dendrimers and the dendrons was verified by an in vitro screening in a selection of tumor cell lines, in parallel with the EPR results. [ABSTRACT FROM AUTHOR]