Staphylococcus epidermidis biofilm on implant material is reduced by a covalently linked thiophenone.

AIMS: The present aims were firstly to coat metal implant material with a quorum sensing inhibitory thiophenone molecule, and secondly to assess the inhibitory effect on Staphylococcus epidermidis biofilm accumulation on thiophenone-coated coupons. METHOD AND RESULTS: Thiophenone- and control-coated metal coupons were prepared by silane hydrolysis and dip coating. The linking of thiophenone to the surface was confirmed by X-ray photoelectron spectroscopy analyses. Biofilm by Staph. epidermidis, a frequent cause of implant-associated infections, was allowed to form under flowing conditions for 48 h. The biofilm accumulations were significantly reduced on the thiophenone-coated coupons. This was confirmed by confocal scanning microscopy. CONCLUSION: This study showed for the first time how a synthetic thiophenone may be covalently linked to a stainless steel surface, and that biofilm accumulations on such surfaces are significantly reduced. SIGNIFICANCE AND IMPACT OF THE STUDY: Functionalizing surfaces by covalent linking of thiophenones might open a wide array of applications. Thiophenone coating of medical implants represents a novel and promising approach to prevent implant-associated infections.

A Comparative Study of the Dispersion of Multi-Wall Carbon Nanotubes Made by Arc-Discharge and Chemical Vapour Deposition.

A method has been developed to characterize the dispersion of multi-wall carbon nanotubes in water using a disc centrifuge for the detection of individual carbon nanotubes, residual aggregates, and contaminants. Carbon nanotubes produced by arc-discharge have been measured and compared with carbon nanotubes produced by chemical vapour deposition. Studies performed on both pristine (see text) arc-discharge nanotubes is rather strong and that high ultra-sound intensity is required to achieve complete dispersion of carbon nanotube bundles. The logarithm of the mode of the particle size distribution of the arc-discharge carbon nanotubes was found to be a linear function of the logarithm of the total ultrasonic energy input in the dispersion process.

Surface dilatational elasticity of poly(oxy ethylene)-based surfactants by oscillation and relaxation measurements of sessile bubbles.

Surface dilatational elasticities and viscosities have been measured by means of the axisymmetric bubble shape method. Two different techniques using sinusoidal oscillations and step relaxations have been used, and the results are treated by means of the bulk/surface diffusional exchange model. Three different nonionic surfactants based on poly(oxy ethylene) as the hydrophilic group have been used: one simple surfactant, Brij 35, and two block copolymers, Pluronic F68 and P9400. Step relaxation and oscillation give mostly the same limiting surface dilatational elasticities, but step relaxation is a more model-dependent method. In the cases where the bulk/surface diffusion model is correct, the two methods give the same results, but otherwise step relaxation gives average values of the limiting elasticity E0 and the typical relaxation frequency omega0. Limiting elasticities up to ca. 25 mN m(-1)have been found for these substances. The surface/bulk diffusion model describes quite well the two relatively hydrophilic substances Brij 35 and F68, especially at low concentrations, but less so for the more hydrophobic P9400. The surface dilatational elasticity as a function of the surface pressure of the surface-active polymers goes through at least one maximum as a result of surface conformational changes.

Surface modification of EPDM rubber by plasma treatment.

The effect of argon, oxygen, and nitrogen plasma treatment of solvent cast EPDM rubber films has been investigated by means of atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and surface energy measurements. Plasma treatment leads to changes in the surface energy from 25 to 70 mN/m. Treatment conditions influenced both the changes in surface energy and the stability, and it became more difficult to obtain good contact angle measurements after longer (> ca. 4 min) treatment times, probably because of an increasingly uneven surface structure. XPS analyses revealed that up to 20 at. % oxygen can be easily incorporated and that variations of approximately 5% can be controlled by the plasma conditions. Oxygen was mainly found in hydroxyl groups, but also as carbonyl and carboxyl. XPS analyses showed more stable surfaces than expected from contact angles, probably because XPS analysis is less surface sensitive than contact angle measurements. AFM measurements revealed different surface structures with the three gases. The surface roughness increased generally with treatment time, and dramatic changes could be observed at longer times. At short times, surface energy changes were much faster than the changes in surface structure, showing that plasma treatment conditions can be utilized to tailor both surface energies and surface structure of EPDM rubber.