Influence of oxygen content on the antibacterial effect of Ag-O coatings deposited by magnetron sputtering

Ag and AgOx thin films were deposited by pulsed DC magnetron sputtering, for medical devices, in order to provide antibacterial properties. During the deposition process, oxygen flow, and, consequently, oxygen fraction, was varied (0â15 sccm) to understand the influence of oxygen species in the physical, chemical and structural properties of thin films. Coatings morphology was observed by scanning electron microscopy (SEM) and their nanostructure and composition were assessed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS), respectively. XRD and XPS analyses revealed that Ag thin films are composed by metallic Ag, which crystallizes in fcc-Ag phase; whereas AgOx showed a mixture of Ag2O and AgO phases for low oxygen fraction that became single AgO with the increase of oxygen fraction in the discharge. Surface wettability and surface tension of the coatings were also determined showing hydrophobic character. Halo inhibition zone tests were performed against Staphylococcus epidermidis, in order to evaluate the antibacterial behavior of coatings, and silver ion release was measured. Only AgOx presented antibacterial behavior, showing that the presence of silver oxide are the main reasons for the antibacterial effect, probably due to the increased production of ROS (Reactive Oxygen Species),making these coatings promising for medical applications.The authors acknowledgments the financial support of FCTFundação para a Ciência e Tecnologia through grant SFRH/BD/90321/2012. Also thank support by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013, and projects ERA-SIINN/0004/2013 through the “Fundo Europeu de Desenvolvimento Regional” (FEDER)

Electrochemical vs antibacterial characterization of ZrCN-Ag coatings

Nowadays, antibacterial properties are becoming a viable feature to be introduced in biomaterials due to the possibility of modifying the materials' surface used in medical devices in a micro/nano metric scale. As a result, it is mandatory to understand the mechanisms of the antimicrobial agents currently used and their possible failures. In this work, the antibacterial activity of ZrCNAg films is studied, taking into consideration the ability of silver nanoparticles to be dissolved when embedded into a ceramic matrix. The study focuses on the silver release evaluated by glow discharge optical emission spectroscopy and the effect of the fluid composition on this release. The results revealed a very low silver release of the films, leading to non-antibacterial activity of such materials. The silver release was found to be dependent on the electrolyte composition. NaCl (8.9 g L? 1) showed the lowest spontaneously silver ionization, while introducing the sulfates in Hanks' balanced salt solution (HBSS) such ionization is increased; finally, the proteins incorporated to the (HBSS) showed a reduction of the silver release, which also explains the low ionization in the culture medium (tryptic soy broth) that contains high quantities of proteins.This research is partially sponsored by the FEDER funds through the program COMPETE - Programa Operacional Factores de Competitividade and by the Portuguese national funds through FCT-Fundacao para a Ciencia e a Tecnologia, under the projects ANTIMICROBCOAT - PTDC/CTM/102853/2008 and in the framework of the Strategic Projects PEST-C/FIS/UI607/2011, PEST-C/EME/UI0285/2011 and SFRH/BD/80947/2011.This work has also been supported by the Ministerio de Ciencia e Innovacion of Spain through the Consolider-Ingenio 2010 Programme (CSD2008-00023) and through project RyC2007-0026

An experimental and theoretical study on the crystal structure and elastic properties of Ta1-xOx coatings

The production of Ta1-xOx coatings has attracted a lot of attention due to their wide variety of industrial applications. Nonetheless, to properly control the functional properties of these coatings, a good understanding of their structural properties must be achieved. Ta1-xOx phases have structural similarities since they are formed by the distortion of the body centered cubic (bcc) Ta structure and, therefore, a clear and unequivocal identification of the crystalline phases is not trivial. In this regard, this work proposes a theoretical and experimental study to understand the evolution of the structural and the elastic properties of Ta-based coatings. The coatings were deposited by magnetron sputtering as a function of oxygen content and characterized by EPMA (electron probe microanalysis), XRD (X-ray diffraction), STEM (scanning transmission electron microscopy) and SAW (surface acoustic waves). The results demonstrate the formation of a bcc alpha-Ta phase in the non-reactive Ta coating, which transitions to a mixture of crystalline tantalum and tantalum oxide phases for low oxygen concentrations while amorphous phases are observed for high oxygen levels. Ab-initio calculations of different Ta-O phases are in good agreement with the experimental results and reveal that the oxygen addition to the metallic Ta phase, leads to a distortion of the Ta crystal structure, causing a decrease in density and an increase of the elastic constants.- This research is sponsored by FEDER funds through the program COMPETE -Programa Operacional Factores de Competitividade and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013, and UID/EMS/00285/2013 and with a PhD fellowship SFRH/BD/98199/2013. The authors also thank the financial support in the framework of ERA-SIINN/0004/2013 and PTDC/CTM-NAN/4242/2014 projects

Ag+ release inhibition from ZrCN–Ag coatings by surface agglomeration mechanism : structural characterization

Published 17 July 2013New multifunctional materials based on well-established materials to which functional properties are added, such as antibacterial performance, have become a relevant research topic, in order to meet the requirements of today's technological advances. This paper reports the results of a detailed structural and chemical characterization study of ZrCN–Ag coatings produced by reactive magnetron sputtering, as well as the release of silver after immersion in a simulated body fluid (Hank's balanced salt solution), which mimic the material behaviour within the human body. The chemical composition was evaluated by electron probe microanalysis, x-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy, whereas the structure was assessed by Raman spectroscopy and x-ray diffraction. The material exhibits a homogeneous distribution of the elements throughout the films, with a (C + N)/Zr ratio of around 1.3 and 15 at% of silver. A mixture of amorphous (a-C and CNx) and crystalline phases (ZrCN) was identified. In addition, the silver was detected to be released in less than 0.7% of the total silver in the films, occurring during the first two hours of immersion; no further release was evidenced after this period of time.This research is partially sponsored by FEDER funds through the program COMPETE-Programa Operacional Factores de Competitividade and by Portuguese national funds through FCT-Fundacao para a Ciencia e a Tecnologia, under the projects ANTIMICROBCOAT-PTDC/CTM/102853/2008. This work has also been supported by the Ministerio de Ciencia e Innovacion of Spain through the Consolider-Ingenio 2010 programme (CSD2008-00023) and through project RyC2007-0026

Influence of the surface morphology and microstructure on the biological properties of Ti-Si-C-N-O coatings

Detailed structural, microstructural, biofilm formation and cytotoxicity studies were performed on Ti-Si-C-ON hard coatings prepared by dc reactive magnetron sputtering, in order to evaluate the relation among these properties. Compositional analysis showed the existence of two distinct regimens; regime I: high C/Si atomic ratio (C/Si ≥1,42) and intermediate N/Ti atomic ratio; regime II: low C/Si atomic ratio (C/Si≤0, 49) and low N/Ti atomic ratio. The structural analysis revealed that, in regime I, films crystallized in a B1-NaCl crystal structure typical of TiC0.2 N0.8. In regime II, the decrease of C/Si and increase in silicon concentration led to the formation of Ti-Si-CON along with a reduction of grain size in the films. Atomic Force Microscopy observations showed that the surface morphology of these Ti-Si-C-ON films became smoother when the silicon content increased and the nitrogen content decreased, which is consistent with the formation of nanosized clusters. Concerning biological properties, it was observed that cytotoxicity could be related with the titanium concentration while biofilm formation ability was found to be related with the surface morphology of the films.The authors are grateful to Dr. Alicia Andres, Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), for her assistance in carrying out the Raman spectroscopic analysis. The project was financially supported by the CRUP Institution (project "Accao N0 E-1007/08"), and the Spanish Ministry of Science and Innovation (projects FUNCOAT CSD2008-00023 and HP2007-0116)

Zn-Fe flower-like nanoparticles growth by gas condensation

Bimetallic nanoparticles have gained attention in the last decade due to their unusual characteristics compared to monometallic counterparts. However, production of such particles with controlled morphologies and composition need to be explored and the mechanisms understood. In this work, we demonstrate a fast and simple process to obtain flower-like Zn-Fe (Zinc-Iron) nanoparticles (NPs) using a hybrid system based on the combination of conventional magnetron sputtering and a cluster beam source. The morphology and structure were characterized by Scanning transmission electron microscopy (STEM), while the chemical composition was evaluated by simultaneous acquisition of Energy-dispersive X-ray spectroscopy (EDS) and Electron energy loss spectroscopy (EELS). Besides, molecular dynamic simulations were used to model the nanoparticle collisions during the simultaneous production, revealing the formation mechanisms of the flower-like nanoparticles.The authors thank the financial support by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020 and by project NANOXYPACK cofinanced via FEDER (PT2020) POCI-01-0145-FEDER-030789.info:eu-repo/semantics/publishedVersio

Resistivity of Mixed-Phase Manganites

The resistivity $\rho_{dc}$ of manganites is studied using a random-resistor-network, based on phase-separation between metallic and insulating domains. When percolation occurs, both as chemical composition and temperature vary, results in good agreement with experiments are obtained. Similar conclusions are reached using quantum calculations and microscopic considerations. Above the Curie temperature, it is argued that ferromagnetic clusters should exist in Mn-oxides. Small magnetic fields induce large $\rho_{dc}$ changes and a bad-metal state with (disconnected) insulating domains.Comment: 4 pages, 4 eps figure

Casimir type effects for scalar fields interacting with material slabs

We study the field theoretical model of a scalar field in presence of spacial inhomogeneities in form of one and two finite width mirrors (material slabs). The interaction of the scalar field with the defect is described with position-dependent mass term. For the single layer system we develop a rigorous calculation method and derive explicitly the propagator of the theory, S-matrix elements and the Casimir self-energy of the slab. Detailed investigation of particular limits of self-energy is presented, and connection to know cases is discussed. The calculation method is found applicable to the two mirrors case as well. By means of it we derive the corresponding Casimir energy and analyze it. For particular values of the parameters of the model the obtained results recover the Lifshitz formula. We also propose a procedure to obtain unambiguously the finite Casimir \textit{self}-energy of a single slab without reference to any renormalizations. We hope that our approach can be applied to calculation of Casimir self-energies in other demanded cases (such as dielectric ball, etc.)Comment: 22 pages, 3 figures, published version, significant changes in Section 4.

Landscape of stimulation-responsive chromatin across diverse human immune cells.

A hallmark of the immune system is the interplay among specialized cell types transitioning between resting and stimulated states. The gene regulatory landscape of this dynamic system has not been fully characterized in human cells. Here we collected assay for transposase-accessible chromatin using sequencing (ATAC-seq) and RNA sequencing data under resting and stimulated conditions for up to 32 immune cell populations. Stimulation caused widespread chromatin remodeling, including response elements shared between stimulated B and T cells. Furthermore, several autoimmune traits showed significant heritability in stimulation-responsive elements from distinct cell types, highlighting the importance of these cell states in autoimmunity. Allele-specific read mapping identified variants that alter chromatin accessibility in particular conditions, allowing us to observe evidence of function for a candidate causal variant that is undetected by existing large-scale studies in resting cells. Our results provide a resource of chromatin dynamics and highlight the need to characterize the effects of genetic variation in stimulated cells

Short-term psychoanalytic psychotherapy with a depressed adolescent with Borderline Personality Disorder: an empirical, single case study

While clinical descriptions of psychotherapy with depressed adolescents with traits of borderline functioning exist, they are not yet supported by empirically-grounded research. This single-case study aims to identify meaningful therapist-patient interaction in the course of short-term psychoanalytic psychotherapy with an adolescent girl who meets diagnostic criteria for both Borderline Personality Disorder (BPD) and Major Depressive Disorder (MDD). Twenty-eight sessions of psychotherapy were coded, using the Adolescent Psychotherapy Q-Set. Five interaction structures were identified, which were distinguished by the nature of the adolescent’s emotional expression during sessions, and how the therapist responded to the young person. Exploration of the clinical and theoretical meaning of these interaction structures suggests that core elements of a young person’s depression and borderline functioning can be identified in sessions, and that the therapeutic process overall shows some significant departures from some of what is usually recognised as a typical psychoanalytic approach. The paper discusses whether these changes in technique can be understood as responses to the clinical challenges associated with working with adolescents with borderline features