National Institute Of Materials Physics - Romania

The present study is focused on the synthesis, characterization and antifungal evaluation of zinc-doped hydroxyapatite (Zn:HAp) coatings. The Zn:HAp coatings were deposited on a pure Si (Zn:HAp_Si) and Ti (Zn:HAp_Ti) substrate by a sol-gel dip coating method using a zinc-doped hydroxyapatite nanogel. The nature of the crystal phase was determined by X-ray diffraction (XRD). The crystalline phase of the prepared Zn:HAp composite was assigned to hexagonal hydroxyapatite in the P6(3/m) space group. The colloidal properties of the resulting Zn:HAp (x(Zn) = 0.1) nanogel were analyzed by Dynamic Light Scattering (DLS) and zeta potential. Scanning Electron Microscopy (SEM) was used to investigate the morphology of the zinc-doped hydroxyapatite (Zn:HAp) nanogel composite and Zn:HAp coatings. The elements Ca, P, O and Zn were found in the Zn:HAp composite. According to the EDX results, the degree of Zn substitution in the structure of Zn:HAp composite was 1.67 wt%. Moreover, the antifungal activity of Zn:HAp_Si and Zn:HAp_Ti against Candida albicans (C. albicans) was evaluated. A decrease in the number of surviving cells was not observed under dark conditions, whereas under daylight and UV light illumination a major decrease in the number of surviving cells was observed.

We investigated the evolution of the DC magnetic hysteresis curves of Nb0.89Ti0.11 alloys thermo-mechanically processed by intermediate heat treatments at 900 degrees C in vacuum and cold rolling (similar to 50% thickness reduction). Starting with a rectangular piece (similar to 0.4 mm thick) cut from the as-grown alloy, after the first thermo-mechanical treatment, the specimen exhibits over a wide temperature T interval a peak effect not far from the DC irreversibility line. With a supplemental thermo-mechanical treatment, the peak effect disappears and is substituted by a second magnetization peak ( where the characteristic fields are significantly lower) induced by pinning enhancement. The second magnetization peak was clearly seen at high temperatures only, due to the occurrence of thermo-magnetic instabilities in the low-T domain. In both cases, analysis of magnetic relaxation evidences a crossover towards plastic vortex creep accompanying the maximum in the effective critical current density. These results suggest a common nature of the observed effects, related to the disordering of the vortex system induced by pinning.

The present work was focused on the synthesis and characterization of hydroxyapatite doped with low concentrations of zinc (Zn: HAp) (0.01 < x(Zn) < 0.05). The incorporation of low concentrations of Zn2+ ions in the hydroxyapatite (HAp) structure was achieved by co-precipitation method. The physico-chemical properties of the samples were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), zeta-potential, and DLS and N2-BET measurements. The results obtained by XRD and FTIR studies demonstrated that doping hydroxyapatite with low concentrations of zinc leads to the formation of a hexagonal structure with lattice parameters characteristic to hydroxyapatite. The XRD studies have also shown that the crystallite size and lattice parameters of the unit cell depend on the substitutions of Ca2+ with Zn2+ in the apatitic structure. Moreover, the FTIR analysis revealed that the water content increases with the increase of zinc concentration. Furthermore, the Energy Dispersive X-ray Analysis (EDAX) and XPS analyses showed that the elements Ca, P, O, and Zn were found in all the Zn: HAp samples suggesting that the synthesized materials were zinc doped hydroxyapatite, Ca10-Zn-x(x)(PO4) (6)(OH), with 0.01 <= x(Zn) <= 0.05. Antimicrobial assays on Staphylococcus aureus and Escherichia coli bacterial strains and HepG2 cell viability assay were carried out.

We report the synthesis of dextran-coated iron oxide magnetic nanoparticles (DIO-NPs) with spherical shape and uniform size distribution as well as their accumulation and toxic effects on Jurkat cells up to 72 h. The characterization of dextran-coated maghemite nanoparticles was done by X-ray diffraction and dynamic light scattering analyses, transmission electron microscopy imaging, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, magnetic hysteresis, and relaxometry measurements. The quantification of DIO-NPs intracellular uptake showed a progressive accumulation of iron as a function of time and dose accompanied by additional lysosome formation and an increasing darkening exhibited by a magnetic resonance imaging (MRI) scanner. The cytotoxicity assays revealed a decrease of cell viability and a loss of membrane integrity in a time-and dose-dependent manner. Exposure to DIO-NPs determined an increase in reactive oxygen species level up to 72 h. In the first two days of exposure, the level of reduced glutathione decreased and the amount of malondyaldehyde increased, but at the end of the experiment, their concentrations returned to control values. These nanoparticles could be used as contrast agents for MRI but several parameters concerning their interaction with the cells should be taken into consideration for a safe utilization.

In the present work we study the optical, struc-tural and morphological properties of CdS-doped glass films, deposited by Pulsed Laser Deposition (PLD) method. The glass target used for ablation was prepared by conventional melt-quenching technique and the semiconductor dopant, CdS powder, was embedded in the borosilicate melt glass host by continuous stirring. In order to improve the properties of the films, the laser wavelength was modified. Photoluminescence emission (PL) of CdSdoped glass films revealed a broad band located in the visible range. The structural analysis was carried out by micro-Raman spectroscopy, pointing out specific vibration modes for Si-O-Si bonds as well as for CdS dopant. The morphology and the chemical characterization of the films were investigated by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and Atomic Force Microscopy (AFM).

In this study, one side aligned PANI coated micro-fibers were fabricated in order to develop a novel actuator configuration. Thus, electrospun PMMA fibers were coated only on one side with a thin gold layer guiding in this way the deposition of PANI (only on the side with gold considering an adequate PANI deposition time). Further, the half-metalized fibers were employed as working microelectrodes for electrochemical deposition of PANI. The prepared PANI coated fibers present actuation properties when they are in contact with an electrolyte like 1 M H2SO4. By switching the potential between +1.4 and -0.2 V, the fiber strips move due to the swelling/shrinking and anisotropic deposition of PANI film.

An Ag:HAp (x(Ag) = 0.5) powder was deposited by thermal evaporation technique as coating on a silicon substrate previously covered with a polydimethylsiloxane (PDMS) layer. The Ag: HAp-PDMS layers were characterized by Scanning ElectronMicroscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and Fourier Transform Infrared Spectroscopy (FT-IR). By infrared spectroscopy analysis, the phase composition of the Ag: HAp-PDMS layers was investigated. The antimicrobial activity of Ag: HAp-PDMS layers was tested against Escherichia coli, Staphylococcus aureus, and Candida albicans microbial strains. The microbial activity decreases significantly for the surveyed time intervals on Ag: HAp-PDMS layers.

Wetting properties of wool textiles were studied either for the raw samples or for those functionalized via covering them at low temperature with nanoparticles of titanium dioxide or zinc oxide. Oxygen plasma pretreatment was performed before deposition. Characterization used optical examination, scanning electron microscopy, infrared spectroscopy, thermogravimetry, X-ray diffraction. Wetting properties were tested under static conditions by estimating the water contact angle. The sessile drop method was applied. The deposited matter represents 3 to 8 wt%, covering rather uniformly the fiber surface. Treated samples show mostly lower values of contact angle than the pristine ones. Cassie-Baxter model is discussed in relation to the equilibrium contact angle of the support.

The aim of our study was to synthesize and evaluate the physicochemical and biological properties of composite films based on poly(lactic-co-glycolic acid) copolymer and quercetin (PLGA/Q) microspheres. During our experiments, we firstly synthesized the PLGA/Q microspheres by using an oil-in-water emulsion-diffusion-evaporation method. Subsequently, the as-prepared composite material was subjected to the matrix assisted pulsed laser evaporation (MAPLE) technique, in order to obtain the PLGA/Q coatings. Relevant compositional and microstructural features of the synthesized samples were obtained by means of Fourier transform infrared spectroscopy (FTIR) and AFM (atomic force microscopy). The long-term biocompatibility of the synthesized films was in vitro evaluated by cellular viability and immunofluorescence assays.