National Institute Of Materials Physics - Romania

Usually, before being used in biomedical applications, a biomaterials' bioactivity is tested by in vitro methods that simulate similar conditions to those found in the human body. In this work, we report on the synthesis of zinc-doped hydroxyapatite-chitosan (ZnHApC) composite coatings by the vacuum deposition method. The surface microstructure and the chemical and molecular modification of the coatings before and after soaking in DMEM (Dulbecco's Modified Eagle's Medium) were studied. For this objective, techniques such as attenuated total reflection (ATR), Fourier transform infrared (FTIR) spectroscopy, metallographic microscopy (MM), and scanning electron microscopy (SEM) were applied used. Also, water contact angle measurements and swelling studies were made on ZnHApC composite coatings before and after soaking in a biological medium. The coatings' adherence to the substrate was also studied. The results of antifungal studies on ZnHApC composite coatings against the Candida albicans microbial strain reveal their good antifungal activity. The biocompatibility of the composite coatings was tested using a primary osteoblast cell line. Our results suggest that zinc-doped hydroxyapatite-chitosan samples could be used as a bioimplant material due to their enhanced bioactivity and biocompatibility.

In this study, we report on the synthesis of L-Cysteine (L-Cys)-coated magnetic iron oxide nanoparticles (NPs) loaded with doxorubicin (Dox). The Fe3O4-L-Cys-Dox NPs were extensively characterized for their compositional and morpho-structural features using EDS, SAED, XRD, FTIR and TEM. XPS, Mossbauer spectroscopy and SQUID measurements were also performed to determine the electronic and magnetic properties of the Fe3O4-L-Cys-Dox nanoparticles. Moreover, by means of a FO-SPR sensor, we evidenced and confirmed the binding of Dox to L-Cys. Biological tests on mouse (B16F10) and human (A375) metastatic melanoma cells evidenced the internalization of magnetic nanoparticles delivering Dox. Half maximum inhibitory concentration IC50 values of Fe3O4-L-Cys-Dox were determined for both cell lines: 4.26 mu g/mL for A375 and 2.74 mu g/mL for B16F10, as compared to 60.74 and 98.75 mu g/mL, respectively, for unloaded controls. Incubation of cells with Fe3O4-L-Cys-Dox modulated MAPK signaling pathway activity 3 h post-treatment and produced cell cycle arrest and increased apoptosis by 48 h. We show that within the first 2 h of incubation in physiological (pH = 7.4) media, similar to 10-15 mu M Dox/h was released from a 200 mu g/mL Fe3O4-L-Cys-Dox solution, as compared to double upon incubation in citrate solution (pH = 3), which resembles acidic environment conditions. Our results highlight the potential of Fe3O4-L-Cys-Dox NPs as efficient drug delivery vehicles in melanoma therapy.

This work was devoted to the first multi-parametric unitary comparative analysis of a selection of sintered piezoceramic materials synthesised by solid-state reactions, aiming to delineate the most promising biocompatible piezoelectric material, to be further implemented into macro-porous ceramic scaffolds fabricated by 3D printing technologies. The piezoceramics under scrutiny were: KNbO3, LiNbO3, LiTaO3, BaTiO3, Zr-doped BaTiO3, and the (Ba0.85Ca0.15)(Ti0.9Zr0.1)O-3 solid solution (BCTZ). The XRD analysis revealed the high crystallinity of all sintered ceramics, while the best densification was achieved for the BaTiO3-based materials via conventional sintering. Conjunctively, BCTZ yielded the best combination of functional properties-piezoelectric response (in terms of longitudinal piezoelectric constant and planar electromechanical coupling factor) and mechanical and in vitro osteoblast cell compatibility. The selected piezoceramic was further used as a base material for the robocasting fabrication of 3D macro-porous scaffolds (porosity of similar to 50%), which yielded a promising compressive strength of similar to 20 MPa (higher than that of trabecular bone), excellent cell colonization capability, and noteworthy cytocompatibility in osteoblast cell cultures, analogous to the biological control. Thereby, good prospects for the possible development of a new generation of synthetic bone graft substitutes endowed with the piezoelectric effect as a stimulus for the enhancement of osteogenic capacity were settled.

The changes of properties and preferential interactions based on subtle energetic differences are important characteristics of organic molecules, particularly for their functionalities in biological systems. Only slightly energetically favored interactions are important for the molecular adsorption and bonding to surfaces, which define their properties for further technological applications. Here, prochiral tetracenothiophene molecules are adsorbed on the Cu(111) surface. The chiral adsorption configurations are determined by Scanning Tunneling Microscopy studies and confirmed by first-principles calculations. Remarkably, the selection of the adsorption sites by chemically different moieties of the molecules is dictated by the arrangement of the atoms in the first and second surface layers. Furthermore, we have investigated the thermal effects on the direct desulfurization reaction that occurs under the catalytic activity of the Cu substrate. This reaction leads to a product that is covalently bound to the surface in chiral configurations.

A novel electrochemical biosensor was developed to monitor fibroblast cells stress levels for the first time in situ under external stimuli based on the recognition of superoxide anion released upon cell damage. The biosensor comprised metallized polycaprolactone electrospun fibers covered with zinc oxide for improved cell adhesion and signal transduction, whilst stable bioconjugates of mercaptobenzoic acid-functionalized gold nanoparticles/ superoxide dismutase were employed as recognition bioelements. Biosensors were first tested and optimized for in situ generated superoxide detection by fixed potential amperometry at +0.3 V, with minimal interferences from electroactive species in cell culture media. L929 fibroblast cells were then implanted on the optimized biosensor surface and the biosensor morphologically characterized by scanning electron microscopy (SEM) and fluorescence microscopy, which illustrated the network-type pattern of fibroblasts adjacent to the fiber scaffold. Fibroblast stress was induced by zymosan and monitored at the cells integrated biosensor using fixed potential amperometry (CA) with a sensitivity of 26 nA cm-2 mu g mL-1 zymosan and electrochemical impedance spectros-copy (EIS), with similar sensitivity of the biosensor considering the Rs and Z' parameters of around 0.13 omega cm2 mu g-1 mL and high correlation factors R2 of 0.9994. The obtained results underline the applicability of the here developed biosensor for the electrochemical screening of the fibroblast cells stress. The concept in using low-cost biocompatible polymeric fibers as versatile scaffolds for both enzyme immobilization and cell adhesion, opens a new path in developing biosensors for the in-situ investigation of a variety of cellular events.

The microscopic mechanism of the occurrence of ferroelectric properties in M-type barium hexaferrites is investigated by experimental and first-principle computation methods. The analysis of magnetic, X-ray, and Mossbauer measurements of BaFe12O19 samples ascertains the correlation between the thermal factor in the process of annealing samples and their functional properties. The occurrence of the remnant polarization in barium hexaferrites at room temperature contradicts the description of their crystal structure in the fra-mework of centrosymmetric space group P63/mmc (No. 194), in which one of the symmetry operations is inversion center. Therefore, the crystal structure of BaFe12O19 was analyzed in the frameworks of SG P63/mmc (No. 194) and non-centrosymmetric SG P63mc (No. 186). The computed value of polarization for a non-centrosymmetric unit cell is similar to 3.5 mu C/cm2. The analysis of polarization was carried out on a path connecting the polar P63mc and non-polar P63/mmc structures and considered in terms of the total energy barrier. Our result allows ascertaining a direct relationship between the remnant polarization of the unit cell and the broken spatial-inversion symmetry in the crystal structure of M-type barium hexaferrite.(c) 2022 Elsevier B.V. All rights reserved.

Pb(Zr,Ti)O-3 (PZT) is the most common ferroelectric (FE) material widely used in solid-state technology. Despite intense studies of PZT over decades, its intrinsic band structure, electron energy depending on 3D momentum k, is still unknown. Here, Pb(Zr0.2Ti0.8)O-3 using soft-X-ray angle-resolved photoelectron spectroscopy (ARPES) is explored. The enhanced photoelectron escape depth in this photon energy range allows sharp intrinsic definition of the out-of-plane momentum k and thereby of the full 3D band structure. Furthermore, the problem of sample charging due to the inherently insulating nature of PZT is solved by using thin-film PZT samples, where a thickness-induced self-doping results in their heavy doping. For the first time, the soft-X-ray ARPES experiments deliver the intrinsic 3D band structure of PZT as well as the FE-polarization dependent electrostatic potential profile across the PZT film deposited on SrTiO3 and LaxSrMn1-xO3 substrates. The negative charges near the surface, required to stabilize the FE state pointing away from the sample (P+), are identified as oxygen vacancies creating localized in-gap states below the Fermi energy. For the opposite polarization state (P-), the positive charges near the surface are identified as cation vacancies resulting from non-ideal stoichiometry of the PZT film as deduced from quantitative XPS measurements.

Multifunctional magnetic nanocomposites are among those heterogeneous nanosized systems where at least one phase component is magnetic and can act as an intermediate of either the actuation or the response of the overall system. The main advantage of heterogeneous nanosystems is the possibility of combining and inter-influencing the electronic properties of constituent interfaced nanophases. Consequently, unique physico-chemical properties of the hybrid materials of interest in various applications can be obtained. This Special Issue of Nanomaterials highlights the most advanced processing and characterization tools of some multifunctional magnetic nanocomposites and heterogeneous systems of interest in various applications, from biomedicine to sensoristics and energy-saving materials.

In our work, the kinetics of martensitic transformations and the influence of thermal treatments on martensitic transformations, as well as the related magnetic properties of the Ni49Mn32Ga19 ferromagnetic shape memory melt-spun ribbons, have been investigated. Thermal treatments at 673 K for 1, 4 and 8 h can be considered an instrument for fine-tuning the performance parameters of alloys. One-hour thermal treatments promote an improvement in the crystallinity of these otherwise highly textured ribbons, reducing internal defects and stress induced by the melt-spinning technique. Longer thermal treatments induce an important magnetization rise concomitantly with a slight and continuous increase in martensitic temperatures and transformation enthalpy. The activation energy, evaluated from differential scanning calorimeter experimental data with a Friedman model, significantly increases after thermal treatments as a result of the multi-phase coexistence and stabilization of the non-modulated martensitic phase, which increases the reverse martensitic transformation hindrance.

The p-n junctions are the building blocks of nowadays electronic devices. The n- or p-type conductivity is obtained in classic semiconductors, like Si, by doping with atoms acting as donors or acceptors, respectively. Doping was used in ferroelectrics to influence the transition temperature, magnitude of some physical properties, but not necessarily conduction type. Therefore, comprehensive studies to obtain true ferroelectric p-n junctions by controlled doping are missing. Recently, it has been shown that Pb(Zr0.2Ti0.8)O-3 films doped with & AP;1% atomic Nb (n-type doping) or Fe (p-type doping) have different orientations of polarization in the as-grown state. Knowing that polarization orientation depends on doping type, the next step is to build ferroelectric p-n homojunctions and to study their properties in relation to ferroelectric polarization. p-n and n-p structures were grown for this purpose by successive deposition of Nb-doped and Fe-doped Pb(Zr,Ti)O-3 layers with different thicknesses. We find that these p-n homojunctions are ferroelectric, but the magnitude of the polarization and coercive field, as well as the dominant polarization orientation in the as-grown state, depend on the conduction type of the first grown layer. The I-V characteristics are quasi-linear, although the interfaces with the electrodes behaves as Schottky contacts. The resistance extracted from the I-V characteristics displays an exponential dependence on temperature, with an activation energy in the range of 0.14-0.17 eV. These results are explained assuming that the total current in the junction is the total of electron and hole injections at the electrode interfaces. It is shown that for relatively low doping concentrations, the current density contains a dominant term with a linear voltage dependence and an exponential temperature dependence, as observed experimentally, and a secondary (correction) term that is dependent on the free carrier density and can induce non-linear voltage dependence when this density is significant.