Several synthetic approaches have been employed to obtain novel {ScM(μ4-pmdc)2(H2O)2·solv} n EHU1(Sc,M) (where M = Li, Na; pmdc = pyrimidine-4,6-dicarboxylate; solv = corresponding solvent) ...compounds. The synthesis method is crucial to determine the type of alkaline that could be hosted in the structure as well as the crystallinity, adsorption performance, and ionic conductivity of the resulting materials. Compared with other synthetic methods, a heat-assisted solvent-free procedure has proven to be the most effective route, giving materials with adsorption capacities close to those expected from GCMC (Grand Canonical Monte Carlo) calculations. Despite the presence of alkaline ions in the framework, the pristine materials exhibit rather low conductivity values of ca. 10–7 S cm–1. The concentration of charge carriers has been increased by means of a doping approach that incorporates divalent transition metal ions to the structure and forces an increase of the alkaline ions, thus raising the ionic conductivity by 1 order of magnitude. Additionally, soaking the samples in solutions containing alkaline salts led to materials possessing an even higher number of carriers achieving conductivity values among the best results reported for MOFs at room temperature, i.e., 4.2 × 10–4 and 9.2 × 10–5 S cm–1 for EHU1(Sc,Li) and EHU1(Sc,Na) obtained by the solvent-free procedure, respectively.
Brain-derived neurotrophic factor (BDNF) regulates dendritic branching and dendritic spine morphology, as well as synaptic plasticity and long-term potentiation. Consequently, BDNF deficiency has ...been associated with some neurological disorders such as Alzheimer's, Parkinson's or Huntington's diseases. In contrast, elevated BDNF levels correlate with recovery after traumatic central nervous system (CNS) injuries. The utility of BDNF as a therapeutic agent is limited by its short half-life in a pathological microenvironment and its low efficacy caused by unwanted consumption of non-neuronal cells or inappropriate dosing. Here, we tested the activity of chitosan microsphere-encapsulated BDNF to prevent clearance and prolong the efficacy of this neurotrophin. Neuritic growth activity of BDNF release from chitosan microspheres was observed in the PC12 rat pheochromocytoma cell line, which is dependent on neurotrophins to differentiate via the neurotrophin receptor (NTR). We obtained a rapid and sustained increase in neuritic out-growth of cells treated with BDNF-loaded chitosan microspheres over control cells (
< 0.001). The average of neuritic out-growth velocity was three times higher in the BDNF-loaded chitosan microspheres than in the free BDNF. We conclude that the slow release of BDNF from chitosan microspheres enhances signaling through NTR and promotes axonal growth in neurons, which could constitute an important therapeutic agent in neurodegenerative diseases and CNS lesions.
Although aminoglycosides are one of the common classes of antibiotics that have been widely used for treating infections caused by pathogenic bacteria, the evolution of bacterial resistance ...mechanisms and their inherent toxicity have diminished their applicability. Biocompatible carrier systems can help sustain and control the delivery of antibacterial compounds while reducing the chances of antibacterial resistance or accumulation in unwanted tissues. In this study, novel chitosan gel beads were synthesized by a double ionic co-crosslinking mechanism. Tripolyphosphate and alginate, a polysaccharide obtained from marine brown algae, were employed as ionic cross-linkers to prepare the chitosan-based networks of gel beads. The in vitro release of streptomycin and kanamycin A was bimodal; an initial burst release was observed followed by a diffusion mediated sustained release, based on a Fickian diffusion mechanism. Finally, in terms of antibacterial properties, the particles resulted in growth inhibition of Gram-negative (
) bacteria.
A series of thermoplastic polymer electrolytes have been prepared employing poly(ethylene oxide) (PEO) as a polymer matrix, bis(trifluoromethane sulfonimide) (LiTFSI), and different room-temperature ...ionic liquids (RTIL) with bis(fluorosulfonyl)imide (FSI) or TFSI anions. This formulation makes them safe and non-flammable. The electrolytes have been processed in the absence of solvents by melt compounding at 120 °C, using sepiolite modified with d-α-tocoferol-polyethyleneglycol 1000 succinate (TPGS-S) as a physical cross-linker of PEO. Several concentrations of RTILs, lithium salt, and TPGS-S have been tested in order to obtain the highest ionic conductivity (σ) without losing electrolytes' mechanical stability. The materials' rheology and ionic conductivity have been extensively characterized. The excellent crosslinking ability of TPGS-S makes the electrolytes behave as thermoplastic materials, even those with the highest liquid concentration. The electrolytes with the highest concentrations of FSI anion present a σ over 10
S·cm
at 25 °C and close to 10
S·cm
at 70 °C, and notably behave as solids at temperatures up to 90 °C despite over 65 wt % of their formulation being liquid. The electrolytes thus obtained are safe solid thermoplastics prepared by industrially scalable procedures and are suitable for energy storage devices, proving the adequacy of polymer-based materials as solid electrolytes for batteries or supercapacitors.
This work describes proton transport in membranes cast from dimethyl sulfoxide solutions of polyelectrolytes obtained by polycondensation of 4,4′-diaminodiphenyl ether (ODA) and 4,4′-diaminodiphenyl ...ether-2,2′-disulfonic acid (ODADS) with 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), the moles of sulfonated diamine per mole of unsulfonated one being roughly 3/1. Pulsed field gradient (PFG) NMR studies reveal two kinds of water: water located in the pores of the membranes appearing in the range 5 to 1 ppm and a minor amount of water associated with the imide groups, appearing at 1 ppm. The diffusion coefficient of 1H in the first type of water is about 2 orders of magnitude higher than that measured in the second type and in both cases the values of this parameter severely decrease as the water content of the membranes decreases. The diffusion coefficients of bare protons, hydronium ions and water in the membranes were calculated using molecular dynamics techniques. For membranes with low water content, the diffusion coefficient of 1H is very close to the diffusion coefficients of water and hydronium ions obtained by simulation. At high concentrations the simulated values are higher than D(1H). The simulated values obtained for the diffusion coefficients of hydronium ion and water for membranes equilibrated with water are fairly close to those estimated, respectively, from proton conductivity and osmotic measurements. This work suggests that the study of cation-exchange membranes in the acidic form using NMR, conductivity, and molecular dynamics simulation techniques provides useful information on how structure and water content affect transport processes in membranes.
Here, the design, synthesis, and characterization of laser nanomaterials based on dye‐doped methyl methacrylate (MMA) crosslinked with octa(propyl‐methacrylate) polyhedral oligomeric silsesquioxane ...(8MMAPOSS) is reported in relation to their composition and structure. The influence of the silicon content on the laser action of the dye pyrromethene 567 (PM567) is analyzed in a systematic way by increasing the weight proportion of POSS from 1 to 50%. The influence of the inorganic network structure is studied by replacing the 8MMAPOSS comonomer by both the monofunctionalized heptaisobutyl‐methacryl‐POSS (1MMAPOSS), which defines the nanostructured linear network with the POSS cages appearing as pendant groups of the polymeric chains, and also by a new 8‐hydrogenated POSS incorporated as additive to the polymeric matrices. The new materials exhibit enhanced thermal, optical, and mechanical properties with respect to the pure organic polymers. The organization of the molecular units in these nanomaterials is studied through a structural analysis by solid‐state NMR. The domain size of the dispersed phase assures a homogeneous distribution of POSS into the polymer, thus, a continuous phase corresponding to the organic matrix incorporates these nanometer‐sized POSS crosslinkers at a molecular level, in agreement with the transparency of the samples. The silicon–oxygen core framework has to be covalently bonded into the polymer backbone instead of being a simple additive and both the silica content and crosslinked degree exhibit a critical influence on the laser action.
The fascinating properties of polyhedral oligomeric silsesquioxanes (POSS) impel the synthesis and characterization of new hybrid nanomaterials with advanced optical applications. Here, composition–structure–properties relationships of dye‐doped POSS‐based materials are established and allow the demonstration of solid‐state laser action (see figure) that is not only truly competitive but out‐performs their liquid counterparts.
Besides giving rise to oligodendrocytes (the only myelin-forming cell in the Central Nervous System (CNS) in physiological conditions), Oligodendrocyte Precursor Cells (OPCs) are responsible for ...spontaneous remyelination after a demyelinating lesion. They are present along the mouse and human CNS, both during development and in adulthood, yet how OPC physiological behavior is modified throughout life is not fully understood. The activity of adult human OPCs is still particularly unexplored. Significantly, most of the molecules involved in OPC-mediated remyelination are also involved in their development, a phenomenon that may be clinically relevant. In the present article, we have compared the intrinsic properties of OPCs isolated from the cerebral cortex of neonatal, postnatal and adult mice, as well as those recovered from neurosurgical adult human cerebral cortex tissue. By analyzing intact OPCs for the first time with 1H High Resolution Magic Angle Spinning Nuclear Magnetic Resonance (1H HR-MAS NMR) spectroscopy, we show that these cells behave distinctly and that they have different metabolic patterns in function for their stage of maturity. Moreover, their response to Fibroblast Growth Gactor-2 (FGF-2) and anosmin-1 (two molecules that have known effects on OPC biology during development and that are overexpressed in individuals with Multiple Sclerosis (MS)) differs in relation to their developmental stage and in the function of the species. Our data reveal that the behavior of adult human and mouse OPCs differs in a very dynamic way that should be very relevant when testing drugs and for the proper design of effective pharmacological and/or cell therapies for MS.
We report, for the first time to the best of our knowledge, a systematic study to relate the laser action from BODIPY dyes, doped into monolithic hybrid matrices, with the synthetic protocols of the ...final materials prepared via sol‐gel. To this aim, the influence of both the hydrolysis time, increased in a controlled way, and the nature of the neutralization agent (pyridine, 3‐amino‐propyltriethoxy‐silane (APS), N‐3‐(trimethoxysilyl)propyl‐ethylene diamine (TSPDA), and N1‐3‐(trimethoxysilyl)propyl‐ diethylene triamine (TSPTA) on the laser action of PM567, incorporated into hybrid matrices based on copolymers of methyl methacrylate (MMA) and 2‐hydroxyethyl methacrylate (HEMA), with methyltriethoxysilane (TRIEOS) as inorganic precursor, was analyzed. The presence of the amine‐modified silane TSPDA as neutralization agent, which is able at the same time to be anchored to the inorganic network enhancing the inorganic‐organic compatibility through the matrix interphase, and utilization of hydrolysis times lower than 10 minutes, increased significantly the lasing efficiency and photostability of dye. The extension of this study to the laser behavior of BODIPY dyes embedded in other different hybrid materials based on hydrolyzed‐condensed copolymers of MMA with 3‐(trimethoxysilyl)propyl methacrylate (TMSPMA) in a 1/1 volumetric proportion, validates the generalization of the above conclusions, which provide guides for the optimization of the synthesis of organic‐inorganic hybrid materials with optoelectronic innovative applications independently of their composition.
The direct influence of the synthetic protocol on the design and development of organic/inorganic hybrid materials with advanced and innovative applications, especially in the optoelectronic fields, is fully assessed. The control of both the neutralization reaction and the hydrolysis time is found to be a determining factor for the enhancement of the laser action of dyes incorporated into hydrid‐matrix active media for solid‐state dye lasers.
The effect of the treatment with glycolipid derivatives on the metabolic profile of intact glioma cells and tumor tissues, investigated using proton high resolution magic angle spinning ((1)H HR-MAS) ...nuclear magnetic resonance (NMR) spectroscopy, is reported here. Two compounds were used, a glycoside and its thioglycoside analogue, both showing anti-proliferative activity on glioma C6 cell cultures; however, only the thioglycoside exhibited antitumor activity in vivo. At the drug concentrations showing anti-proliferative activity in cell culture (20 and 40 µM), significant increases in choline containing metabolites were observed in the (1)H NMR spectra of the same intact cells. In vivo experiments in nude mice bearing tumors derived from implanted C6 glioma cells, showed that reduction of tumor volume was associated with significant changes in the metabolic profile of the same intact tumor tissues; and were similar to those observed in cell culture. Specifically, the activity of the compounds is mainly associated with an increase in choline and phosphocholine, in both the cell cultures and tumoral tissues. Taurine, a metabolite that has been considered a biomarker of apoptosis, correlated with the reduction of tumor volume. Thus, the results indicate that the mode of action of the glycoside involves, at least in part, alteration of phospholipid metabolism, resulting in cell death.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
: This study was undertaken to determine the best time during the menstrual cycle to perform dynamic breast magnetic resonance imaging (MRI). The contralateral “normal” breast of 50 premenopausal ...women (mean age 40.4 ± 6.4 years, range 30–52 years) were enrolled in a protocol designed to correlate an ipsilateral suspicious breast lesion with pathology. The contralateral breast in each patient was examined with palpation and mammography prior to MRI on a 1.5T scanner using gradient echo and dynamic contrast‐enhanced echo‐planar without and following gadolinium diethylenetriaminepentaacetic acid (Gd‐DTPA) injection. Pre‐contrast T1 relaxation times were measured before calculating extraction flow product (EFP) maps using a multicompartmental model. T1, EFP, and enhancement were measured in the control breast on four slices centered around the nipple and recorded as a function of the phases of the menstrual cycle. Lesions or areas with focal enhancement were excluded. Analysis of variance and Fisher's tests were performed. The cyclic changes in T1 relaxation time were not significant (p > 0.2). EFP and enhancement varied significantly during the cycle (p < 0.003 and p < 0.004, respectively), with low values during the first half of the cycle and high values during the second half. The lowest values of EFP and enhancement (5.5 ± 2.9 ml/100 g/min and 26 ± 17%) were observed during the proliferative phase (days 3–7), and the highest values (17 ± 10.2 ml/100 g/min and 104 ± 28%) were observed during the secretory phase (days 21–27) (p < 0.0006 and p < 0.0008, respectively). Dynamic breast MRI should be performed during first half of the menstrual cycle (days 3–14) in order to minimize interpretative difficulties related to the uptake of gadolinium in normal breast tissue due to hormonal fluctuations during the menstrual cycle.
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