Jef Vleugels

The Nonsteroidal Antiinflammatory Drug Diclofenac Potentiates the In Vivo Activity of Caspofungin Against Candida albicans Biofilms

In this study, we demonstrated that in vitro Candida albicans biofilms grown in the presence of diclofenac showed increased susceptibility to caspofungin. These findings were further confirmed using a catheter-associated biofilm model in rats. C. albicans-inoculated catheters retrieved from rats that were treated with both diclofenac and caspofungin contained significantly fewer biofilm cells and showed no visible biofilms inside the catheter lumens, as documented by scanning electron microscopy, as compared to catheters retrieved from rats receiving only caspofungin or diclofenac. This report indicates that diclofenac could be useful in combination therapy with caspofungin to treat C. albicans biofilm-associated infections.

Staphylococcal biofilm growth on smooth and porous titanium coatings for biomedical applications

Implant-related infections are a serious complication in prosthetic surgery, substantially jeopardizing implant fixation. As porous coatings for improved osseointegration typically present an increased surface roughness, their resulting large surface area (sometimes increasing with over 700% compared to an ideal plane) renders the implant extremely susceptible to bacterial colonization and subsequent biofilm formation. Therefore, there is particular interest in orthopaedic implantology to engineer surfaces that combine both the ability to improve osseointegration and at the same time reduce the infection risk. As part of this orthopaedic coating development, the interest of in vitro studies on the interaction between implant surfaces and bacteria/biofilms is growing. In this study, the in vitro staphylococcal adhesion and biofilm formation on newly developed porous pure Ti coatings with 50% porosity and pore sizes up to 50 μm is compared to various dense and porous Ti or Ti-6Al-4V reference surfaces. Multiple linear regression analysis indicates that surface roughness and hydrophobicity are the main determinants for bacterial adherence. Accordingly, the novel coatings display a significant reduction of up to five times less bacterial surface colonization when compared to a commercial state-of-the-art vacuum plasma sprayed coating. However, the results also show that a further expansion of the porosity with over 15% and/or the pore size up to 150 μm is correlated to a significant increase in the roughness parameters resulting in an ascent of bacterial attachment. Chemically modifying the Ti surface in order to improve its hydrophilicity, while preserving the average roughness, is found to strongly decrease bacteria quantities, indicating the importance of surface functionalization to reduce the infection risk of porous coatings.

Carbon nanofillers for machining insulating ceramics

The implementation of ceramics in emerging applications is principally limited by the final machining process necessary for producing microcomponents with complex geometries. The addition of carbon nanotubes greatly enhances the electrical properties of insulating ceramics allowing electrical discharge machining to be used to manufacture intricate parts. Meanwhile other properties of the ceramic may be either preserved or even improved. For the first time, a silicon nitride/carbon nanotubes microgear is electrically discharge machined with a remarkably high material removal rate, low surface roughness, and low tool wear. This offers unprecedented opportunities for the manufacture of complicated ceramic parts by adding carbon nanotubes for new engineering and biomedical applications.

Highly-translucent, strong and aging-resistant 3Y-TZP ceramics for dental restoration by grain boundary segregation

Latest trends in dental restorative ceramics involve the development of full-contour 3Y-TZP ceramics which can avoid chipping of veneering porcelains. Among the challenges are the low translucency and the hydrothermal stability of 3Y-TZP ceramics. In this work, different trivalent oxides (Al2O3, Sc2O3, Nd2O3 and La2O3) were selected to dope 3Y-TZP ceramics. Results show that dopant segregation was a key factor to design hydrothermally stable and high-translucent 3Y-TZP ceramics and the cation dopant radius could be used as a controlling parameter. A large trivalent dopant, oversized as compared to Zr(4+), exhibiting strong segregation at the ZrO2 grain boundary was preferred. The introduction of 0.2 mol% La2O3 in conventional 0.1-0.25 wt.% Al2O3-doped 3Y-TZP resulted in an excellent combination of high translucency and superior hydrothermal stability, while retaining excellent mechanical properties.

A Current Opinion on Electrophoretic Deposition in Pulsed and Alternating Fields

Electrophoretic deposition (EPD) is a colloidal production process developed in the early 20th century. Industrial scale EPD for the production of electronic components and phosphorescent screens and in the form of cataphoretic painting has known some success. Despite its limited practical applications, the inherent versatility of EPD has never ceased to fuel research into this technique. One of the major drives of this research was to render the method more environmentally friendly by enabling deposition from aqueous suspensions. One particular route, suggested to circumvent the problems caused by the use of water in EPD, is the use of alternating or pulsed fields. Recently, the use of alternating fields in EPD has been investigated for the deposition of biological matter in the form of cells and molecules. With this new avenue of research opening up and coinciding with a rise in biotechnological processes, one can expect a renewed interest in traditional EPD and fundamental research on the use of pulsed and alternating fields in this technique. Hence, this review attempts to summarize a centurys worth of both fundamental and applied research for scientists venturing into the field of EPD.

Thermodynamic prediction of the nonstoichiometric phase Zr1–zCezO2–x in the ZrO2–CeO1.5–CeO2 system

Abstract A thermodynamic estimation of the ZrO 2 –CeO 2 and ZrO 2 –CeO 1.5 systems, as well as the cubic phase in the CeO 1.5 –CeO 2 system has been developed and the complex relation between the nonstoichiometry, y , in Ce z O 2–y and the oxygen partial pressure at different temperatures is evaluated. The behavior of the nonstoichiometry phase Zr 1– z Ce z O 2– x is described based on the thermodynamic estimation in the ZrO 2 –CeO 2 , CeO 1.5 –CeO 2 and ZrO 2 –CeO 1.5 systems. Additionally, the interdependence among miscellaneous factors, which can be used to describe the change in oxidation states of cerium such as the oxygen partial pressure, the CeO 1.5 fraction in CeO 1.5 –CeO 2 in the quasi-ternary system, the nonstoichiometry y and the difference between the activity of CeO 2 and CeO 1.5 are predicted. The calculated results are found to be very useful to explain the influence of pressureless sintering at different O 2 partial pressures on the mechanical properties of CeO 2 -stabilised ZrO 2 ceramics

Isostatic pressing assisted indirect selective laser sintering of alumina components

Purpose – The purpose of this paper is to assess a new powder metallurgy process to make alumina parts through indirect selective laser sintering (SLS). Density measurements, some geometrical assessments and scanning electron microscopy (SEM) microstructural analyses are performed after each stage of the process, allowing an objective overview to be provided of the challenges and possibilities for the processing of high density technical ceramic parts through SLS of ball milled alumina/polyamide powder agglomerates.Design/methodology/approach – The powder production by ball milling, SLS, cold isostatic pressing (CIP) or quasi isostatic pressing (QIP), debinding and sintering (FS) stages of the powder metallurgy process were sequentially investigated.Findings – Alumina parts with a density up to 94.1 per cent could be produced by a powder metallurgy process containing an SLS step. Microstructural investigation of the sintered samples reveals an alumina matrix with a grain size of ∼5 μm and two different ki...

Fungal β-1,3-Glucan Increases Ofloxacin Tolerance of Escherichia coli in a Polymicrobial E. coli/Candida albicans Biofilm

ABSTRACT In the past, biofilm-related research has focused mainly on axenic biofilms. However, in nature, biofilms are often composed of multiple species, and the resulting polymicrobial interactions influence industrially and clinically relevant outcomes such as performance and drug resistance. In this study, we show that Escherichia coli does not affect Candida albicans tolerance to amphotericin or caspofungin in an E. coli/C. albicans biofilm. In contrast, ofloxacin tolerance of E. coli is significantly increased in a polymicrobial E. coli/C. albicans biofilm compared to its tolerance in an axenic E. coli biofilm. The increased ofloxacin tolerance of E. coli is mainly biofilm specific, as ofloxacin tolerance of E. coli is less pronounced in polymicrobial E. coli/C. albicans planktonic cultures. Moreover, we found that ofloxacin tolerance of E. coli decreased significantly when E. coli/C. albicans biofilms were treated with matrix-degrading enzymes such as the β-1,3-glucan-degrading enzyme lyticase. In line with a role for β-1,3-glucan in mediating ofloxacin tolerance of E. coli in a biofilm, we found that ofloxacin tolerance of E. coli increased even more in E. coli/C. albicans biofilms consisting of a high-β-1,3-glucan-producing C. albicans mutant. In addition, exogenous addition of laminarin, a polysaccharide composed mainly of poly-β-1,3-glucan, to an E. coli biofilm also resulted in increased ofloxacin tolerance. All these data indicate that β-1,3-glucan from C. albicans increases ofloxacin tolerance of E. coli in an E. coli/C. albicans biofilm.

Synthesis and characterisation of CeO2-coated ZrO2 powder-based TZP

Abstract A novel technique is described for the preparation of Al2O3-doped CeO2-coated ZrO2 nanopowders from a solution of aluminium nitrate and cerium nitrate in a mixed alcohol/water suspension with monoclinic zirconia (m-ZrO2) powder. Drying of the suspension and subsequent calcination of the powder at 800°C results in alumina-doped CeO2-coated m-ZrO2 nanopowder with a grain size below 100 nm. The as-prepared powder can be pressureless sintered in air at 1450° into dense ceria-stabilised tetragonal polycrystals (Ce-TZP) materials with an excellent fracture toughness of 11 MPa m1/2 and a Vickers hardness of 750 kg/mm2 (HV30). The microstructure and mechanical properties of the alumina-doped CeO2-coated powder-based TZP are compared with that of a Ce-TZP obtained from commercially available co-precipitated powder.

Spark Plasma Sintering As a Solid-State Recycling Technique: The Case of Aluminum Alloy Scrap Consolidation

Recently, “meltless” recycling techniques have been presented for the light metals category, targeting both energy and material savings by bypassing the final recycling step of remelting. In this context, the use of spark plasma sintering (SPS) is proposed in this paper as a novel solid-state recycling technique. The objective is two-fold: (I) to prove the technical feasibility of this approach; and (II) to characterize the recycled samples. Aluminum (Al) alloy scrap was selected to demonstrate the SPS effectiveness in producing fully-dense samples. For this purpose, Al alloy scrap in the form of machining chips was cold pre-compacted and sintered bellow the solidus temperature at 490 °C, under elevated pressure of 200 MPa. The dynamic scrap compaction, combined with electric current-based joule heating, achieved partial fracture of the stable surface oxides, desorption of the entrapped gases and activated the metallic surfaces, resulting in efficient solid-state chip welding eliminating residual porosity. The microhardness, the texture, the mechanical properties, the microstructure and the density of the recycled specimens have been investigated. An X-ray computed tomography (CT) analysis confirmed the density measurements, revealing a void-less bulk material with homogeneously distributed intermetallic compounds and oxides. The oxide content of the chips incorporated within the recycled material slightly increases its elastic properties. Finally, a thermal distribution simulation of the process in different segments illustrates the improved energy efficiency of this approach.