Staphylococcus aureus-Fibronectin Interactions with and without Fibronectin-Binding Proteins and Their Role in Adhesion and Desorption

Adhesion and residence-time-dependent desorption of two Staphylococcus aureus strains with and without fibronectin (Fn) binding proteins (FnBPs) on Fn-coated glass were compared under flow conditions. To obtain a better understanding of the role of Fn-FnBP binding, the adsorption enthalpies of Fn with staphylococcal cell surfaces were determined using isothermal titration calorimetry (ITC). Interaction forces between staphylococci and Fn coatings were measured using atomic force microscopy (AFM). The strain with FnBPs adhered faster and initially stronger to an Fn coating than the strain without FnBPs, and its Fn adsorption enthalpies were higher. The initial desorption was high for both strains but decreased substantially within 2 s. These time scales of staphylococcal bond ageing were confirmed by AFM adhesion force measurement. After exposure of either Fn coating or staphylococcal cell surfaces to bovine serum albumin (BSA), the adhesion of both strains to Fn coatings was reduced, suggesting that BSA suppresses not only nonspecific but also specific Fn-FnBP interactions. Adhesion forces and adsorption enthalpies were only slightly affected by BSA adsorption. This implies that under the mild contact conditions of convective diffusion in a flow chamber, adsorbed BSA prevents specific interactions but does allow forced Fn-FnBP binding during AFM or stirring in ITC. The bond strength energies calculated from retraction force-distance curves from AFM were orders of magnitude higher than those calculated from desorption data, confirming that a penetrating Fn-coated AFM tip probes multiple adhesins in the outermost cell surface that remain hidden during mild landing of an organism on an Fn-coated substratum, like that during convective diffusional flow

An epigenome-wide association study of posttraumatic stress disorder in US veterans implicates several new DNA methylation loci

Background Previous studies using candidate gene and genome-wide approaches have identified epigenetic changes in DNA methylation (DNAm) associated with posttraumatic stress disorder (PTSD). Methods In this study, we performed an EWAS of PTSD in a cohort of Veterans (n = 378 lifetime PTSD cases and 135 controls) from the Translational Research Center for TBI and Stress Disorders (TRACTS) cohort assessed using the Illumina EPIC Methylation BeadChip which assesses DNAm at more than 850,000 sites throughout the genome. Our model included covariates for ancestry, cell heterogeneity, sex, age, and a smoking score based on DNAm at 39 smoking-associated CpGs. We also examined in EPIC-based DNAm data generated from pre-frontal cortex (PFC) tissue from the National PTSD Brain Bank (n = 72). Results The analysis of blood samples yielded one genome-wide significant association with PTSD at cg19534438 in the gene G0S2 (p = 1.19 x 10(-7), p(adj) = 0.048). This association was replicated in an independent PGC-PTSD-EWAS consortium meta-analysis of military cohorts (p = 0.0024). We also observed association with the smoking-related locus cg05575921 in AHRR despite inclusion of a methylation-based smoking score covariate (p = 9.16 x 10(-6)), which replicates a previously observed PGC-PTSD-EWAS association (Smith et al. 2019), and yields evidence consistent with a smoking-independent effect. The top 100 EWAS loci were then examined in the PFC data. One of the blood-based PTSD loci, cg04130728 in CHST11, which was in the top 10 loci in blood, but which was not genome-wide significant, was significantly associated with PTSD in brain tissue (in blood p = 1.19 x 10(-5), p(adj) = 0.60, in brain, p = 0.00032 with the same direction of effect). Gene set enrichment analysis of the top 500 EWAS loci yielded several significant overlapping GO terms involved in pathogen response, including "Response to lipopolysaccharide" (p = 6.97 x 10(-6), p(adj) = 0.042). Conclusions The cross replication observed in independent cohorts is evidence that DNA methylation in peripheral tissue can yield consistent and replicable PTSD associations, and our results also suggest that that some PTSD associations observed in peripheral tissue may mirror associations in the brain.Stress-related psychiatric disorders across the life spa

Hergebruik van thermoplastisch afval in onderdelen van composiet

In dit lectoraatsonderzoek is onderzocht op welke wijze mix-plastics kunnen worden gebonden tot een schuimachtige massa. Achterliggende gedachte is om enerzijds een oplossing te hebben voor het hergebruiken van de mix-plastics en anderzijds hiermee een opvulling te realiseren in composietproducten van hergebruikt materiaal in plaats van nieuw (virgin) schuim om hiermee een hogere mate van circulariteit te krijgen. De mix-plastics zijn niet met conventionele verwerkingstechnieken te recyclen door de heterogeniteit en hoge vervuilingsgraad. Twee methoden van het binden van de mix-plastics tot een schuimachtige massa zijn onderzocht: mengen met een schuimende polyurethaan en mengen met extra PE-bedrijfsafval en vervolgens consolideren door te smelten. Het onderzoek toont dat beide methoden mogelijkheden bieden voor het gebruiken van mix-plastics om hiermee een schuimachtige massa te maken die in nieuwe composietproducten kan worden ingezet

Poedercoaten op plastic : het elektrisch geleidbaar maken van kunststoffen

Poedercoaten is een techniek om op producten een verflaag aan te brengen zonder gebruik te maken van oplosmiddelen. Dit literatuuronderzoek biedt een korte inleiding in de achtergronden van het poedercoaten op deze materialen

Poedercoat op composiet

Poedercoaten is een techniek waarbij verf in poedervorm op een product wordt aangebracht en vervolgens wordt uitgehard in een oven. Poedercoatings worden al tientallen jaren aangebracht op metalen, bijvoorbeeld staal en aluminium. Een voordeel van deze techniek is dat er tijdens het coaten geen Vluchtige Organische Stoffen (VOS) vrijkomen, die brandbaar, explosief en/of giftig zijn. Thermoharde composietmaterialen bestaan uit een vezel gecombineerd met een thermoharde matrix. Producten die gemaakt zijn van composiet materiaal worden veelal van een gelcoat voorzien. Dit is een coatinglaag die een product kleur, uitstraling en bescherming tegen invloeden van buitenaf kan geven. Nadeel van gelcoats gebaseerd op onverzadigde polyester is dat tijdens de verwerking VOS vrijkomen en dat dit een piekbelasting in de emissie veroorzaakt. In plaats van een gelcoat zou een poedercoating kunnen worden aangebracht. Dit is mogelijk wanneer het composietproduct elektrisch geleidend is. Thermoharders zijn dat niet, maar koolstofvezels hebben wel de eigenschap dat ze elektrisch geleidend zijn. In dit onderzoek is koolstof gebruikt om voldoende geleiding te creeëren, waardoor het poeder aangetrokken wordt naar het substraat. Het is mogelijk gebleken om composiet te coaten met de low-bake poedercoating van Koninklijke Van Wijhe Verf. Er is een goede hechting verkregen met de gebruikte polyesterhars en epoxy composieten. Wanneer een koolstofvlies als buitenste laag gebruikt wordt en de proefstukken gepostcured worden levert dit een coatinglaag op met een gedekt en vlak uiterlijk

Kunststoffen in de medische technologie

Beschrijving van enkele cases uitgevoerd door het lectoraat 'Kunststoftechnologie van Hogeschool Windesheim' in het kader van het onderzoeksproject 'Kunststoffen in de Medische Technologie'. De focus lag bij ontwikkelingen voor de medische industrie in meer algemene zin en niet op toepassingen binnen het lichaam

Bond-Strengthening in Staphylococcal Adhesion to Hydrophilic and Hydrophobic Surfaces Using Atomic Force Microscopy

Time-dependent bacterial adhesion forces of four strains of Staphylococcus epidermidis to hydrophobic and hydrophilic surfaces were investigated. Initial adhesion forces differed significantly between the two surfaces and hovered around -0.4 nN. No unambiguous effect of substratum surface hydrophobicity on initial adhesion forces for the four different S. epidermidis strains was observed. Over time, strengthening of the adhesion forces was virtually absent on hydrophobic dimethyldichlorosilane (DDS)-coated glass, although in a few cases multiple adhesion peaks developed in the retract curves. Bond-strengthening on hydrophilic glass occurred within 5-35 s to maximum adhesion forces of -1.9 +/- 0.7 nN and was concurrent with the development of multiple adhesion peaks upon retract. Poisson analysis of the multiple adhesion peaks allowed separation of contributions of hydrogen bonding from other nonspecific interaction forces and revealed a force contribution of -0.8 nN for hydrogen bonding and +0.3 nN for other nonspecific interaction forces. Time-dependent bacterial adhesion forces were comparable for all four staphylococcal strains. It is concluded that, on DDS-coated glass, the hydrophobic effect causes instantaneous adhesion, while strengthening of the bonds on hydrophilic glass is dominated by noninstantaneous hydrogen bond formation

Bond-Strengthening in Staphylococcal Adhesion to Hydrophilic and Hydrophobic Surfaces Using Atomic Force Microscopy

Time-dependent bacterial adhesion forces of four strains of Staphylococcus epidermidis to hydrophobic and hydrophilic surfaces were investigated. Initial adhesion forces differed significantly between the two surfaces and hovered around -0.4 nN. No unambiguous effect of substratum surface hydrophobicity on initial adhesion forces for the four different S. epidermidis strains was observed. Over time, strengthening of the adhesion forces was virtually absent on hydrophobic dimethyldichlorosilane (DDS)-coated glass, although in a few cases multiple adhesion peaks developed in the retract curves. Bond-strengthening on hydrophilic glass occurred within 5-35 s to maximum adhesion forces of -1.9 +/- 0.7 nN and was concurrent with the development of multiple adhesion peaks upon retract. Poisson analysis of the multiple adhesion peaks allowed separation of contributions of hydrogen bonding from other nonspecific interaction forces and revealed a force contribution of -0.8 nN for hydrogen bonding and +0.3 nN for other nonspecific interaction forces. Time-dependent bacterial adhesion forces were comparable for all four staphylococcal strains. It is concluded that, on DDS-coated glass, the hydrophobic effect causes instantaneous adhesion, while strengthening of the bonds on hydrophilic glass is dominated by noninstantaneous hydrogen bond formation

Mobile and immobile adhesion of staphylococcal strains to hydrophilic and hydrophobic surfaces

Staphylococcus epidermidis adheres to hydrophilic glass and hydrophobic dimethyldichlorosilane (DDS)-coated glass in similar numbers, but in different modes. Real-time observation of staphylococcal adhesion under a shear rate of 15 s(-1) revealed different adhesion dynamics on both substrata. The number of adsorption and desorption events to achieve a similar number of adhering bacteria was twofold higher on hydrophilic than on hydrophobic DDS-coated glass. Moreover. 22% of all staphylococci on glass slid over the surface prior to adhering on a fixed site ("mobile adhesion mode"), but mobile adhesion was virtually absent (1%) on DDS-coated glass. Sliding preceded desorption on hydrophilic glass in about 20% of all desorption events, while on hydrophobic DDS-coated glass 2% of all staphylococci desorbed straight from their adhesion site. Since acid-base interactions between the staphylococci and a hydrophobic DDS-coating are attractive, it is suggested that these interactions facilitate a closer approach of the bacteria and therewith enhance immobile adhesion at local, high affinity sites. Alternatively, if the local site is low affinity, this may lead to desorption. In the absence of attractive acid-base interactions, as on hydrophilic glass, bacteria can be captured in the minimum of the DLVO-interaction energy curve, but this does not prevent them from sliding under flow at a fixed distance from a substratum surface until immobilization or desorption at or from a local high or low affinity site, respectively