Surface modification of polymer textile biomaterials by N2 supercritical jet: Preliminary mechanical and biological performance assessment.

Foreign Body Reaction (FBR) is a critical issue to be addressed when polyethylene terephthalate (PET) textile implants are considered in the medical field to treat pathologies involving hernia repair, revascularization strategies in arterial disease, and aneurysm or heart valve replacement. The natural porosity of textile materials tends to induce exaggerated tissue ingrowth which may prevent the implants from remaining flexible. One hypothesized way to limit the FBR process is to increase the material surface roughness at the yarn level. Supercritical N2 (ScN2) jet particle projection is a technique that provides enough velocity to particles in order to induce plastic deformation on the impacted surface. This work investigates the influence of ScN2 jet projection parameters like standoff distance or particle size on the roughness that can be obtained on medical polymer yarns of various diameters (100 and 400 µm) and woven textile surfaces obtained from a 100 µm yarn. Moreover, the mechanical and biological performances of the obtained modified textile material are assessed. Results bring out that with appropriate testing conditions (500 bars jet/500 mm distance between nozzle and PET textile) and particle size around 50 µm, it is possible to generate 20 µm large and 4 µm deep craters on a 100 µm monofilament PET yarn and fabric. Regarding the strength of the textile material, it is only slightly modified with the treatment process, as the tenacity of the yarns decreases by only 10%. Moreover, It is shown that the obtained structures tend to limit the adhesion and slow down the proliferation of human fibroblasts.

Water density and polarizability deduced from the refractive index determined by interferometric measurements up to 250 MPa.

The refractive index of water is precisely determined in the visible light range as a function of the pressure until 250 MPa by means of a new measurement device that uses a special pipe tee included in an interferometer set. This technique allows revisiting the Bradley-Tait and Sellmeier equations to make them dependent on the wavelength and the pressure, respectively. The Bradley-Tait equation for the pressure dependence of the water refractive index is completed by a wavelength-dependent factor. Also, in the considered pressure and wavelength ranges, it is shown that the Sellmeier coefficients can be straightforwardly linked to the pressure, allowing the determination of the refractive index of water for either any wavelength or pressure. A new simple model allows the determination of the density of water as a function of the measured refractive index. Finally, the polarizability of water as function of pressure and wavelength is calculated by means of the Lorentz-Lorenz equation.