1 - ArticleThe surface of polypropylene was modified by the post-irradiation grafting of acrylic acid (AAc), N,N-dimethylacrylamide (DMA) and mixtures of AAc (DMA) and a quaternary ammonium salt (QAS). The polypropylene sheets were activated by electron beam radiation before the grafting reaction. The degree of grafting was determined by weighing and the surface hydrophilicity was measured by measuring the water contact angles. The presence of oxygen and nitrogen was demonstrated by XPS. The surface charge and the isoelectric point were determined by the streaming potential method. The grafting of DMA, like that of AAc, depended on monomer availability, but the monomer did not permeate into the polypropylene bulk. For the same surface hydrophilicity, depending on the nature of the monomer or comonomer grafted, it is possible to modulate the physicochemical characteristics which determine the phenomena governing adhesion, and probably to adapt them to a given application
A radial flow chamber was used to experimentally study the detachment kinescopes of deformable (Dictyostelium discoideum) and non-deformable (Saccharomyces cerevisiae) cells. In both cases, phenomenological laws were derived, defining detachment efficiency and a detachment rate. A microscopic model was proposed, which explains the stress dependence of the detachment rate and of the efficiency and their dependence when the surface is changed. The specificities of living cells compared to passive bodies and more precisely the role of the cytoskeleton are outlined. It is shown that the presence of the cytoskeleton retards cells peeling off from the surface due to the emission of pseudopods, whereas cells without cytoskeleton peel off in a passive manner. These observations set the limits of the present approach and the necessary ingredients in the further developments.
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