Specific nanoprobe design for MRI: Targeting laminin in the blood-brain barrier to follow alteration due to neuroinflammation.

Chronic neuroinflammation is characterized by increased blood-brain barrier (BBB) permeability, leading to molecular changes in the central nervous system that can be explored with biomarkers of active neuroinflammatory processes. Magnetic resonance imaging (MRI) has contributed to detecting lesions and permeability of the BBB. Ultra-small superparamagnetic particles of iron oxide (USPIO) are used as contrast agents to improve MRI observations. Therefore, we validate the interaction of peptide-88 with laminin, vectorized on USPIO, to explore BBB molecular alterations occurring during neuroinflammation as a potential tool for use in MRI. The specific labeling of NPS-P88 was verified in endothelial cells (hCMEC/D3) and astrocytes (T98G) under inflammation induced by interleukin 1ß (IL-1ß) for 3 and 24 hours. IL-1ß for 3 hours in hCMEC/D3 cells increased their co-localization with NPS-P88, compared with controls. At 24 hours, no significant differences were observed between groups. In T98G cells, NPS-P88 showed similar nonspecific labeling among treatments. These results indicate that NPS-P88 has a higher affinity towards brain endothelial cells than astrocytes under inflammation. This affinity decreases over time with reduced laminin expression. In vivo results suggest that following a 30-minute post-injection, there is an increased presence of NPS-P88 in the blood and brain, diminishing over time. Lastly, EAE animals displayed a significant accumulation of NPS-P88 in MRI, primarily in the cortex, attributed to inflammation and disruption of the BBB. Altogether, these results revealed NPS-P88 as a biomarker to evaluate changes in the BBB due to neuroinflammation by MRI in biological models targeting laminin.

Tuning electronic and magnetic properties through disorder in V2O5 nanoparticles.

We report on the synthesis and characterization of V2O5 nanoparticles grown using a sol-gel method at different calcination temperatures. We observed a surprising reduction in the optical band gap from 2.20 to 1.18 eV with increasing calcination temperature from 400 to 500 °C. Raman and X-Ray diffraction measurements indicated slight changes in the lattice parameters induced by the growth process. However, density functional theory calculations of the Rietveld-refined and pristine structures revealed that the observed optical gap reduction could not be explained by structural changes alone. By introducing oxygen vacancies to the refined structures, we could reproduce the reduction of the band gap. Our calculations also showed that the inclusion of oxygen vacancies at the vanadyl position creates a spin-polarized interband state that reduces the electronic band gap and promotes a magnetic response due to unpaired electrons. This prediction was confirmed by our magnetometry measurements, which exhibited a ferromagnetic-like behavior. Our findings suggest that oxygen vacancies play a crucial role in band gap reduction and the promotion of a ferromagnetic-like response in an otherwise paramagnetic material. This provides a promising route to engineer novel devices.

Control of Multiferroic properties in BiFeO3 nanoparticles.

BiFeO3 (BFO) nanoparticles (NPs) were synthesized using the sol-gel method at different calcination temperatures from 400 °C to 600 °C. XRD studies have confirmed that all BFO NPs show distorted rhombohedral crystals that match the R3c space group. We found evidence of local structural strain that develops with increasing particle size as suggested by TEM and Raman spectroscopy measurements. Magnetic measurements suggest that NPs have two distinct regimes: a ferromagnetic-like one at low temperatures and a superparamagnetic-like one at room temperature. The crossover temperature increases with NPs size, suggesting a size-dependent blocking magnetic regime. Similarly, local piezoelectric measurements at room temperature in single NP have confirmed a ferroelectric order with a NP size-dependent d33 coefficient. An analysis of both the ferroelectric and the magnetic results suggest that ferromagnetism and ferroelectricity coexist at room temperature in NPs. Our results lead to the possibility of tailoring the ferroic order in multifunctional materials by means of NP size.

Synthesis, characterization, X-ray crystal structure and DFT calculations of 4-([2,2':6',2 '' -terpyridin]-4'-yl)phenol / Síntesis, caracterización, estructura cristalina y cálculos DFT para el 4-([2,2':6',2 '' -terpiridin]-4'-il)fenol / Síntese, caracterização, estrutura de cristal e cálculos DFT para o 4-([2,2':6',2 '' -terpiridina]-4'-il)fenol

Abstract The synthesis of new terpyridine (Tpy) derivatives has been subject of extensive research due to its potential as functional materials for solar energy conversion, among other applications. In this contribution, the 4-([2,2':6',2"-terpyndm]-4'-yl)phenol (TpyOH) was synthesized, characterized and studied through several methods, including X-ray crystallography and computational approaches. Single crystal X-ray structure analysis shows that TpyOH is essentially planar, with dihedral angles of about 5.03° between the central pyridinyl and the phenolic ring, and also 6.05 and 12.2° in the terpyridine moiety. In the crystal, molecules are linked by intermolecular hydrogen bonds and through П- П stacking interactions. Using a time dependent density functional theory approach and taking into account bulk solvent effects, the absorption and fluorescence spectra of TpyOH were investigated and compared. The TD-DFT S0→Sn and S1 →S0 transition energies are in good agreement with experimental results. The frontier molecular orbitals analysis showed that the low-energy absorption band has an intraligand charge transfer character (ICT), while the high-energy band is a common feature of П- П* transitions of the Tpy moiety. The S1→S0 emission transition also has an ICT character, with a 90% contribution from the HOMO→LUMO transitions.

Resumen La síntesis de derivados terpiridinicos (Tpy) se ha investigado ampliamente debido a su potencial para la conversión de energía solar En este artículo se sintetizó y caracterizó el 4-([2,2':6',2"-terpiridin]-4'-il)fenol (TpyOH), a través de varias metodologías como la cristalografía de rayos X y herramientas computacionales. El análisis de rayos X de monocristal mostró que el TpyOH es plano, con ángulos diedros de 5,03° entre el piridinilo central y el anillo fenólico, con presencia de ángulos de 6,05 y 12,2° en la porción terpiridínica. En el cristal, las moléculas están unidas por enlaces de hidrógeno intermoleculares y mediante interacciones de apilamiento n-n. Utilizando cálculos DFT dependientes del tiempo (TD-DFT) y teniendo en cuenta el efecto de los disolventes, se investigaron y compararon los espectros de absorción y fluorescencia de TpyOH. Las energías de transición TD-DFT de S0→Sn y S1→S0 concuerdan con los resultados experimentales. El análisis de orbitales moleculares de frontera mostró que la banda de absorción de baja energía corresponde a transferencia de carga intraligando (ICT); mientras que la banda de alta energía es común en las transiciones П-П* del resto Tpy. La emisión debido a la transición S1→S0 corresponde a ICT, con una contribución del 90% proveniente de transiciones HOMO→LUMO.

Resumo A síntese de derivados de terpiridina (Tpy) tem sido estudada devido ao seu potencial para a conversão de energia solar. Nesta contribuição, o 4-([2,2':6',2"- terpindina]-4'-il) fenol (TpyOH) foi sintetizado, caracterizado e estudado por vários métodos A análise de estrutura de raios X de cristal único mostra que o TpyOH é plano, com Ångulos diedros de 5,03 ° entre o piridinilo central e o anel fenólico, e também 6,05 e 12,2 ° na porção de terpiridina No cristal, as moléculas são ligadas por ligações intermoleculares de hidrogênio e através de interações de empilhamento n-n. Usando uma abordagem da teoria funcional da densidade dependente do tempo e levando em consideração os efeitos do solvente em massa, foram investigados e comparados os espectros de absorção e fluorescência do TpyOH As energias de transição TD-DFT S0→Sn e S1→S0 estão de acordo com os resultados experimentais A análise de orbitários moleculares de fronteira mostrou que a banda de absorção de baixa energia possui um caráter de transferência de carga intraligando (TIC), enquanto a banda de alta energia é uma característica comum das transições П-П* da fração Tpy. A transição de emissão S1→S0 também tem um caráter TIC, com uma contribuição de 90% das transições HOMO→LUMO.

Influence of saline and pH on collagen type I fibrillogenesis in vitro: fibril polymorphism and colloidal gold labelling.

We have produced different collagen type I fibrils by in vitro fibrillogenesis of acetic acid-soluble collagen within the pH range 2.5-9.0, in the presence and absence of 150 mM NaCl. The varying relatively stable molecular assemblies and polymorphic fibrillar end-products produced after 24 h incubation have been assessed and compared by the TEM study of specimens negatively stained with uranyl acetate. In the presence of 150 mM NaCl, the assembly of collagen at low pH (2.5) leads to the formation of initial molecular aggregates that progressively link together at slightly higher pH (5.0) to form sub-fibrils and spindle-shaped D-banded bundles of sub-fibrils. At pH 6.0 these D-banded bundles aggregate into larger spindle-shaped fibrils with lateral misalignment of the D-banding across the bundle. However, at pH 7.0 and 8.0, in the presence of 150 mM NaCl, the characteristic parallel-sided mature D-banded collagen type I fibres are formed. At pH 9.0 more loosely formed parallel-sided D-banded collagen fibrils are present, within which the spindle-shaped sub-fibrils can be defined by negative staining more convincingly than at pH 7-8. In the presence of 50 mM buffer at pH 2.5, but absence of 150 mM NaCl, collagen type I forms disorganized periodic initial molecular aggregates, which have a tendency to link together to form sub-fibrils. Flexuous collagen type I sub-fibrils predominate at pH 5.0, alongside large spindle-shaped fibrils that possess a regular transverse approximately 10 nm periodicity, with an oblique approximately 67 nm periodicity, significantly different to the D-banding periodicity. At pH 7.0 and pH 8 in the absence of saline loosely-formed flexuous and spindle-shaped fibres co-exist, with underlying sub-fibrils visible, but at pH 9.0 only disorganized flexuous fibrillar aggregates are present. Colloidal gold labelling of the characteristic D-banded collagen type I fibrils with 5 nm and 2 nm chemically reactive gold particles reveals a periodic labelling pattern, which is not apparent with 10 nm and 15 nm gold particles, due to steric hindrance. The flexuous and spindle-shaped collagen fibrils also bind 2 nm gold particles in a specific manner. In all cases, the specific chemisorption of gold onto the collagen fibrils is probably determined by the availability of repeating amino acid side chains of the collagen molecules along the fibril surface. The controlled production of varying stable collagen type I fibrillogenesis products is likely to be of value within numerous areas of biotechnology, biology and medicine, including experimental biomineralization.

Novel photoreception system in sponges? Unique transmission properties of the stalk spicules from the hexactinellid Hyalonemasieboldi.

Sponges (phylum Porifera) of the classes Hexactinellida and Demospongiae possess a skeleton composed of siliceous spicules, which are synthesized enzymatically. The longest spicules are found among the Hexactinellida, with the stalk spicules (length: 30 cm; diameter: 300 microm) of Hyalonema sieboldi as prominent examples. These spicules are constructed around a central axial filament, which is formed by approximately 40 siliceous layers. The stratified spicules function as optical glass fibers with unique properties. If free-spaced coupled with a white light source (WLS), the entire fiber is illuminated. Special features of the light transmission: (i) only wavelengths between 615 and 1310 nm can pass through the fibers and (ii) light below wavelengths of 615 nm and above 1310 nm is completely cut-off. The transmission efficiency is around 60% (measured at 1080-1100 nm [length of the fiber: 5 cm]). The spicules acts as sharp high- and low-pass filters, suggesting that these silica-based fibers might be involved in a photoreception system. This assumption is supported by the finding that sponges are provided with a bioluminescent system. It is hypothesized that the spicules/siliceous fibers might be involved in a photoreception system in these animals.

Magnetic resonance imaging of the siliceous skeleton of the demosponge Lubomirskia baicalensis.

The skeletal elements (spicules) of the demosponge Lubomirskia baicalensis were analyzed; they are composed of amorphous, non-crystalline silica, and contain in a central axial canal the axial filament which consists of the enzyme silicatein. The axial filament, that orients the spicule in its longitudinal axis exists also in the center of the spines which decorate the spicule. During growth of the sponge, new serially arranged modules which are formed from longitudinally arranged spicule bundles are added at the tip of the branches. X-ray analysis revealed that these serial modules are separated from each other by septate zones (annuli). We describe that the longitudinal bundles of spicules of a new module originate from the apex of the earlier module from where they protrude. A cross section through the oscular/apical-basal axis shows that the bundle rays are organized in a concentric and radiate pattern. High resolution magnetic resonance microimaging studies showed that the silica spheres of the spicules in the cone region contain high amounts of 'mobile' water. We conclude that the radiate accretive growth pattern of sponges is initiated in the apical region (cones) by newly growing spicules which are characterized by high amounts of 'mobile' water; subsequently spicule bundles are formed laterally around the cones.

Mineralization of SaOS-2 cells on enzymatically (silicatein) modified bioactive osteoblast-stimulating surfaces.

There is a demand for novel bioactive supports in surgery, orthopedics, and tissue engineering. The availability of recombinant silica-synthesizing enzyme (silicatein) opens new possibilities for the synthesis of silica-containing bioactive surfaces under ambient conditions that do not damage biomolecules like proteins. Here it is shown that growth of human osteosarcoma SaOS-2 cells on cluster plates precoated with Type 1 collagen is not affected by additional coating of the plates with the recombinant silicatein and incubation with its enzymatic substrate, tetraethoxysilane (TEOS). However, the enzymatic modification of the plates by biosilica deposition on the protein-coated surface caused a marked increase in calcium phosphate formation of SaOS-2 cells as revealed by alizarin red-S staining to quantify calcium mineral content. The increased occurrence of calcium-phosphate nodules on the modified surface was also observed by scanning electron microscopy. These results suggest that by supporting calcium-phosphate deposition in vitro, biosilica (silicatein)-modified surfaces are potentially bioactive in vivo, by stimulating osteoblast mineralization function.

Formation of siliceous spicules in the marine demosponge Suberites domuncula.

The siliceous skeleton of demosponges is constructed of spicules. We have studied the formation of spicules in primmorphs from Suberites domuncula. Scanning electron microscopy and transmission electron-microscopical (TEM) analyses have revealed, in the center of the spicules, an axial canal that is 0.3-1.6 microm wide and filled with an axial filament. This filament is composed of the enzyme silicatein, which synthesizes the spicules. TEM analysis has shown that spicule formation starts intracellularly and ends extracellularly in the mesohyl. At the initial stage, the axial canal is composed only of silicatein, whereas membranous structures and fibrils (10-15 nm in width) can later also be identified, suggesting that intracellular components protrude into the axial canal. Antibodies against silicatein have been applied for Western blotting; intracellularly, silicatein is processed to the mature form (24 kDa), whereas the pro-enzyme with the propeptide (33 kDa) is detected extracellularly. Silicatein undergoes phosphorylation at five sites. Immunohistological analysis has shown that silicatein exists in the axial canal (axial filament) and on the surface of the spicules, suggesting that they grow by apposition. Finally, we have demonstrated that the enzymic reaction of silicatein is inhibited by anti-silicatein antibodies. These data provide, for the first time, a comprehensive outline of spicule formation.

Molybdenum blue: binding to collagen fibres and microcrystal formation.

Collagen fibres have been shown by transmission electron microscopy to progressively bind the polyoxomolybdate ring-complex, termed molybdenum blue. Nucleation of cuboidal molybdenum blue microcrystals occurs on the surface of the collagen fibres, leading eventually to extensive coating of the fibres with microcrystals.