Novel multiferroic state and ME enhancement by breaking the AFM frustration in LuMn1-xO3.

This study provides a comprehensive insight into the effects of controlled off-stoichiometry on the structural and multiferroic properties of the hexagonal manganite LuMn1-xO3+δ (x = 0.02; δ ∼ 0), supported by neutron powder diffraction measurements confirming single phase P63cm symmetry and evidencing a relevant ferromagnetic component, below TN ∼ 90 K, which breaks the archetypal geometrically frustrated antiferromagnetic state typically ascribed to LuMnO3. The perturbations in the triangular disposition of spins prompt an additional electric polarization contribution and a clear enhancement of the magnetoelectric coupling which are in good agreement with the results of first principles calculations. In addition, Raman spectroscopy, dielectric permittivity, pyroelectric current and magnetic measurements as a function of temperature point out the precursor effects of the magnetic phase transitions involving a strong coupling between spins, lattice and electric order, even above the Néel temperature.

Breaking the geometric magnetic frustration in controlled off-stoichiometric LuMn1+zO3+δ compounds.

This study explores controlled off-stoichiometric LuMn1+zO3+δ (|z| < 0.1) compounds, intended to retain the utter LuMnO3 intrinsic hexagonal symmetry and ferroelectric properties. X-ray powder diffraction measurements evidenced a single phase P63cm structure. Thermo-gravimetric experiments show a narrow impact of oxygen vacancies while a distinguishable gas exchange at ∼700 K, a surprisingly lower temperature when compared to perovskite systems. A comparison of different nominal ceramics revealed pertinent structural and magnetic property variations owing to subtle self-doping effects. Deviations from the archetypal antiferromagnetic state were detected below ∼90 K suggesting local rearrangements of the nominal Mn(3+) ions matrix, breaking the ideal geometrical spin frustration, leading to a non-compensated magnetic structure.

General route to synthesize of metal (Ni, Co, Mn, Fe) oxide nanostructure and their optical and magnetic behaviour.

Here we report a generalised way to prepare transitional metal (Ni, Co, Mn, Fe) oxide nanostructures via solvothermal route followed by controlled heat treatment. The method has been successfully involved to produce structurally uniform and well crystalline phase of the different metal (Ni, Co, Mn) oxide faceted nanoparticles and porous nanorods (Fe2O3) with highly anisotropic surfaces. The product materials were characterized by the X-ray powder diffraction and electron microscope (SEM, TEM) to investigate the structural and morphological details. Optical absorption study was carried out by UV-VIS spectrophotometer and the results are analysed on the basis of their electronic transitions of 3d shell and band energies. The details magnetic investigation was carried out by the measurement of magnetization with varying magnetic field and temperature. The observed magnetic behaviour is explained on the basis of uncompensated spins lying on the surface which is extremely anisotropic in the present systems of the synthesized materials.

Tuning the drug multimodal release through a co-assembly strategy based on magnetic gels.

Self-assembled short peptide-based gels are highly promising drug delivery systems. However, implementing a stimulus often requires screening different structures to obtain gels with suitable properties, and drugs might not be well encapsulated and/or cause undesirable effects on the gel's properties. To overcome this challenge, a new design approach is presented to modulate the release of doxorubicin as a model chemotherapeutic drug through the interplay of (di)phenylalanine-coated magnetic nanoparticles, PEGylated liposomes and doxorubicin co-assembly in dehydropeptide-based gels. The composites enable an enhancement of the gelation kinetics in a concentration-dependent manner, mainly through the use of PEGylated liposomes. The effect of the co-assembly of phenylalanine-coated nanoparticles with the hydrogel displays a concentration and size dependence. Finally, the integration of liposomes as doxorubicin storage units and of nanoparticles as composites that co-assemble with the gel matrix enables the tuneability of both passive and active doxorubicin release through a thermal, and a low-frequency alternating magnetic field-based trigger. In addition to the modulation of the gel properties, the functionalization with (di)phenylalanine improves the cytocompatibility of the nanoparticles. Hereby, this work paves a way for the development of peptide-based supramolecular systems for on-demand and controlled release of drugs.

Exploring human porphobilinogen synthase metalloprotein by quantum biochemistry and evolutionary methods.

Previous studies have shown the porphobilinogen synthase (PBGS) zinc-binding mechanism and its conservation among the living cells. However, the precise molecular interaction of zinc with the active center of the enzyme is unknown. In particular, quantum chemistry techniques within the density functional theory (DFT) framework have been the key methodology to describe metalloproteins, when one is looking for a compromise between accuracy and computational feasibility. Considering this, we used DFT-based models within the molecular fractionation with conjugate caps scheme to evaluate the binding energy features of zinc interacting with the human PBGS. Besides, phylogenetic and clustering analyses were successfully employed in extracting useful information from protein sequences to identify groups of conserved residues that build the ions-binding site. Our results also report a conservative assessment of the relevant amino acids, as well as the benchmark analysis of the calculation models used. The most relevant intermolecular interactions in Zn2+-PBGS are due to the amino acids CYS0122, CYS0124, CYS0132, ASP0169, SER0168, ARG0221, HIS0131, ASP0120, GLY0133, VAL0121, ARG0209, and ARG0174. Among these residues, we highlighted ASP0120, GLY0133, HIS0131, SER0168, and ARG0209 by co-occurring in all clusters generated by unsupervised clustering analysis. On the other hand, the triple cysteines at 2.5 Å from zinc (CYS0122, CYS0124, and CYS0132) have the highest energy attraction and are absent in the taxa Viridiplantae, Sar, Rhodophyta, and some Bacteria. Additionally, the performance of the DFT-based models shows that the processing time-dependence is more associated with the choice of the basis set than the exchange-correlation functional.

Dehydropeptide-based plasmonic magnetogels: a supramolecular composite nanosystem for multimodal cancer therapy.

Supramolecular hydrogels are highly promising candidates as biomedical materials owing to their wide array of properties, which can be tailored and modulated. Additionally, their combination with plasmonic/magnetic nanoparticles to form plasmonic magnetogels further improves their potential in biomedical applications through the combination of complementary strategies, such as photothermia, magnetic hyperthermia, photodynamic therapy and magnetic-guided drug delivery. Here, a new dehydropeptide hydrogelator, Npx-l-Met-Z-ΔPhe-OH, was developed and combined with two different plasmonic/magnetic nanoparticle architectures, i.e., core/shell manganese ferrite/gold nanoparticles and gold-decorated manganese ferrite nanoparticles with ca. 55 nm and 45 nm sizes, respectively. The magnetogels were characterized via HR-TEM, FTIR spectroscopy, circular dichroism and rheological assays. The gels were tested as nanocarriers for a model antitumor drug, the natural compound curcumin. The incorporation of the drug in the magnetogel matrices was confirmed through fluorescence-based techniques (FRET, fluorescence anisotropy and quenching). The curcumin release profiles were studied with and without the excitation of the gold plasmon band. The transport of curcumin from the magnetogels towards biomembrane models (small unilamellar vesicles) was assessed via FRET between the fluorescent drug and the lipid probe Nile Red. The developed magnetogels showed promising results for photothermia and photo-triggered drug release. The magnetogels bearing gold-decorated nanoparticles showed the best photothermia properties, while the ones containing core/shell nanoparticles had the best photoinduced curcumin release.

Effective production of multifunctional magnetic-sensitive biomaterial by an extrusion-based additive manufacturing technique.

A calcium phosphate (CaP)-based scaffold used as synthetic bone grafts, which smartly combines precise dimensions, controlled porosity and therapeutic functions, presents benefits beyond those offered by conventional practices, although its fabrication is still a challenge. The sintering step normally required to improve the strength of the ceramic scaffolds precludes the addition of any biomolecules or functional particles before this stage. This study presents a proof of concept of multifunctional CaP-based scaffolds, fabricated by additive manufacturing from an innovative ink composition, with potential for bone regeneration, cancer treatment by local magnetic hyperthermia and drug delivery platforms. Highly loaded inks comprising iron-doped hydroxyapatite and ß-tricalcium phosphate powders suspended in a chitosan-based solution, in the presence of levofloxacin (LEV) as model drug and magnetic nanoparticles (MNP), were developed. The sintering step was removed from the production process, and the integrity of the printed scaffolds was assured by the polymerization capacity of the ink composite, using genipin as a crosslinking agent. The effects of MNP and LEV on the inks' rheological properties, as well as on the mechanical and structural behaviour of non-doped and iron-doped scaffolds, were evaluated. Magnetic and magneto-thermal response, drug delivery and biological performance, such as cell proliferation in the absence and presence of an applied magnetic field, were also assessed. The addition of a constant amount of MNP in the iron-doped and non-doped CaP-based inks enhances their magnetic response and induction heating, with these effects more pronounced for the iron-doped CaP-based ink. These results suggest a synergistic effect between the iron-doped CaP-based powders and the MNP due to ferro/ferrimagnetic interactions. Furthermore, the iron presence enhances human mesenchymal stem cell metabolic activity and proliferation.

Superferromagnetism in mechanically alloyed fcc Fe(23)Cu(77) with bimodal cluster size distribution.

Magnetic measurements, x-ray diffraction and Mössbauer spectroscopy were used to characterize a nanostructured fcc Fe(23)Cu(77) at.% alloy prepared by high-energy ball-milling, addressing in particular the effect of clustering on the nature of the interacting magnetic entities. The interpretation of magnetization measurements leads to the conclusion that grains, whose mean size is ∼16 nm, contain two populations of magnetic Fe-rich nanoclusters with a bimodal size distribution. These two sets of clusters contain about 14 and 400 Fe atoms and have magnetic moments of 30 µ(B) and 860 µ(B), respectively. The inter-cluster ferromagnetic interactions that lead to superferromagnetism with a Curie temperature T(C)∼220 K can be described by a mean field determined by the smaller clusters only, which account for 90% of the magnetization.

Synthesis of thermoelectric magnesium-silicide pastes for 3D printing, electrospinning and low-pressure spray.

In this work, eco-friendly magnesium-silicide (Mg2Si) semiconducting (n-type) thermoelectric pastes for building components concerning energy-harvesting devices through 3D printing, spray and electrospinning were synthetized and tested for the first time. The Mg2Si fine powders were obtained through the combination of ball milling and thermal annealing under Ar atmosphere. While the latter process was crucial for obtaining the desired Mg2Si phase, the ball milling was indispensable for homogenizing and reducing the grain size of the powders. The synthetized Mg2Si powders exhibited a large Seebeck coefficient of ~ 487 µV/K and were blended with a polymeric solution in different mass ratios to adjust the paste viscosity to the different requirements of 3D printing, electrospinning and low-pressure spray. The materials produced in every single stage of the paste synthesis were characterized by a variety of techniques that unequivocally prove their viability for producing thermoelectric parts and components. These can certainly trigger further research and development in green thermoelectric generators (TEGs) capable of adopting any form or shape with enhanced thermoelectric properties. These green TEGs are meant to compete with common toxic materials such as Bi2Te3, PbTe and CoSb that have Seebeck coefficients in the range of ~ 290-700 µV/K, similar to that of the produced Mg2Si powders and lower than that of 3D printed bulk Mg2Si pieces, measured to be ~ 4866 µV/K. Also, their measured thermal conductivities proved to be significantly lower (~ 0.2 W/mK) than that reported for Mg2Si (≥ 4 W/mK). However, it is herein demonstrated that such thermoelectric properties are not stable over time. Pressureless sintering proved to be indispensable, but difficultly achievable by long thermal annealing (even above 32 h) in inert atmosphere at 400 °C, at least for bulk Mg2Si pieces constituted by a mean grain size of 2-3 µm. Hence, for overcoming this sintering challenge and become the silicide's extrusion viable in the production of bulk thermoelectric parts, alternative pressureless sintering methods will have to be further explored.

Nitropolycyclic aromatic hydrocarbons are inducers of mitotic homologous recombination in the wing-spot test of Drosophila melanogaster.

In this study, the widespread environmental pollutants 1-nitronaphthalene (1NN), 1,5-dinitronaphthalene (1,5DNN), 2-nitrofluorene (2NF) and 9-nitroanthracene (9NA), were investigated for genotoxicity in the wing somatic mutation and recombination test (SMART) of Drosophila--using the high bioactivation (HB) cross. Our in vivo experiments demonstrated that all compounds assessed induced genetic toxicity, causing increased incidence of homologous somatic recombination. 2NF, 9NA and 1NN mutant clone induction is almost exclusively related to somatic recombination, although 1,5DNN-clone induction depends on both mutagenic and recombinagenic events. 1NN has the highest recombinagenic activity (approximately 100%), followed by 2NF (approximately 77%), 9NA (approximately 75%) and 1,5DNN (33%). 1NN is the compound with the strongest genotoxicity, with 9NA being approximately 40 times less potent than the former and 2NF and 1,5DNN approximately 333 times less potent than 1NN. The evidence indicating that the major effect observed in this study is an increased frequency of mitotic recombination emphasizes another hazard that could be associated to NPAHs--the increment in homologous recombination (HR).

Peculiar Magnetoelectric Coupling in BaTiO3:Fe113 ppm Nanoscopic Segregations.

We report polycrystalline BaTiO3 with cooperative magnetization behavior associated with the scarce presence of about 113 atomic ppm of Fe ions, clearly displaying magnetoelectric coupling with significant changes in magnetization (up to ΔM/M ≈ 32%) at the ferroelectric transitions. We find that Fe ions are segregated mostly at the interfaces between grain boundaries and an Fe-rich phase, forming a self-composite with high magnetoelectric coupling above room temperature. We compare our results with ab initio calculations and other experimental results found in the literature, proposing mechanisms that could be behind the magnetoelectric coupling within the ferroelectric matrix. These findings open the way for further strategies to optimize interfacial magnetoelectric couplings.

Hyperfine local probe study of alkaline-earth manganites SrMnO3 and BaMnO3.

We report perturbed angular correlation measurements with (111m)Cd/(111)Cd and (111)In/(111)Cd probes, at the ISOLDE-CERN facility, in the manganite compounds BaMnO3, with the 6H and 15R polymorphs, and SrMnO3, with the 4H polymorph. The electric field gradient (EFG) is measured, and found approximately constant in a large temperature range for all the compounds. The EFG is also calculated from first principles with density functional theory, and compared with experimental results by considering diluted substitutional Cd impurities. Based on the results, we assign as sites for the probes the Ba (for BaMnO3-6H, 15R) and Sr (for SrMnO3-4H) sites, apart from fractions of undetermined origin in the case of BaMnO3-6H. We predict the hyperfine parameters in the recently synthesized multiferroic manganite Sr(0.5)Ba(0.5)MnO3, and its variation with the structure and electric polarization, which is found to be very small.

Jahn-Teller distortion relaxation across the LaMnO3+Δ phase diagram.

The evolution of the local Jahn-Teller distortion across the LaMnO3+Δ phase diagram was obtained using the perturbed angular correlation local probe technique. We found that upon doping, the local distortion decreases continuously with increasing doping and that no fully Jahn-Teller distorted Mn(3+)O6 octahedra are observed within the orthorhombic insulating phase. A local single-phase scenario is established for the orbital disordered orthorhombic crystallographic structure. We also show that the continuous weakening of the Jahn-Teller distortions is not limited to a single-phase environment and occurs in a similar manner within an undistorted rhombohedric matrix upon lowering the temperature.

Assessment of genotoxicity of Lidocaine, Prilonest and Septanest in the Drosophila wing-spot test.

The scope of this study was to characterize the likely interaction Lidocaine, Prilonest and Septanest have with DNA, with a view to quantitatively and qualitatively establishing mutagenic, clastogenic, and/or recombinagenic activity of those compounds. The wing somatic mutation and recombination test in Drosophila melanogaster, which detects simultaneously point and chromosomal mutations as well as recombination induced by the activity of genotoxins of direct and indirect action, was used. Each of the anesthetics was tested at different concentrations, administered orally for 48 h to 3rd-stage larvae, in two independent experiments, with concurrent negative controls. The results obtained revealed that only Prilonest exhibits genotoxic activity in somatic cells, being able to induce exclusively homologous recombination. Additionally, it was possible to conclude that the genotoxic effect attributed to Prilonest is not related to metabolites produced via the P450-type enzymes. However, both Lidocaine and Septanest are unable to induce either events related to gene and chromosomal mutation, or reciprocal recombination.

New phase transition in the Pr1-xCaxMnO3 system: evidence for electrical polarization in charge ordered manganites.

In this Letter a detailed study of the electric field gradient (EFG) across the Pr(1-x)Ca(x)MnO(3) phase diagram and its temperature dependence is given. Clearly, distinct EFG behavior for samples outside or inside the charge order (CO) region are observed. The EFG temperature dependence evidences a new phase transition occurring over the broad CO region of the phase diagram. This transition is discontinuous and occurs at temperatures between the charge ordering and the Néel temperatures. The prominent features observed in the EFG are associated with polar atomic vibrations which eventually lead to a spontaneous local electric polarization below CO transition.

Assessment of Intellectual and Visuo Spatial Abilities in Children and Adults with Williams Syndrome / Evaluación de habilidades intelectuales y visuoespaciales de niños y adultos con Síndrome de Williams

The Williams-Beuren syndrome (SWB), also known as Williams syndrome, is a contiguous gene deletion of the region 7q.11.23. The main clinical characteristics are typical faces, supravalvular aortic stenosis, failure to thrive, short stature, transient neonatal hypercalcemia, delayed language, friendly personality, hyperacusis and intellectual disability. The diagnosis of SWB is confirmed by the detection of micro deletion by different techniques of molecular cytogenetics, FISH, MLPA or polymorphic markers. This study assessed the verbal intelligence quotient (IQ) and performance and visuo-spatial skills in children and adults with WBS. The composed group was of 31 WBS patients (19 M and 12 F), whose ages ranged from 9 to 26 years (M 14.45 y). All patients had the diagnosis confirmed molecularly. The tests used were the WISC-III, WAIS-III and Rey-Osterrieth Complex Figure Test. The results indicated a total IQ ranged from 51 to 86 (M 63): 22 with mild intellectual disability, 4 with moderate intellectual disability, 4 borderlines and 1 below the normal media. All patients had marked visual-spatial deficits. The results suggest nonverbal reasoning, visuo-spatial perception, spatial representation, working memory, motor planning and executive functions are very affected in this group.

El síndrome de Williams-Beuren (SWB), también conocido como síndrome de Williams, es un síndrome de deleción de genes contiguos de la región 7q.11.23. Se caracteriza por dimorfismo facial típico asociado a anomalías cardiovasculares, personalidad amigable, hiperacusia y deficiencia intelectual. El diagnóstico del SWB es confirmado por la detección de microdeleción a partir de las diferentes técnicas de citogenética molecular: FISH, marcadores polimórficos o MLPA. Este estudio evaluó el cociente intelectual verbal y manipulativo, así como las habilidades visuoespaciales en niños y adultos con SWB. El grupo estuvo formado por 31 pacientes con SWB (19 de sexo masculino y 12 de sexo femenino), cuyas edades variaron entre 9 y 26 años (media 14.45 años). Todos los pacientes tenían el diagnóstico confirmado molecularmente. Los test utilizados fueron las escalas WISC-III, WAIS-III y el Test Figuras Complejas Rey-Osterrieth. Los resultados indicaron un cociente intelectual que osciló de 51 a 86 (media 63), distribuido así: 22 con deficiencia intelectual leve, 4 con deficiencia intelectual moderada, 4 limítrofes, 1 en la media inferior. Todos los pacientes presentaron déficit visuoespacial. Los resultados sugieren que el razonamiento no verbal, la percepción visuoespacial, la representación espacial, la memoria de trabajo, la planificación motora y las funciones ejecutivas están muy comprometidos en el grupo estudiado.