In vivo leucocyte interactions on Pellethane surfaces.

In vivo leucocyte interactions of three Pellethane materials of varying hardness were qualitatively and quantitatively characterized using a cage implant system over a 21 d implantation period. Scanning electron microscopy (SEM) and cytochemical staining were utilized to observe the cellular events occurring at the leucocyte-biomaterial interface. Many of the quantitative assays performed, the intracellular alkaline phosphatase activity of exudate leucocytes, the intracellular acid phosphatase activity of adherent leucocytes, the density of adherent leucocytes and the foreign body giant cell network formation tendencies of adherent leucocytes, suggest increased cellular activation with increased Pellethane hardness. Qualitative SEM evaluation of Pellethane surfaces revealed a variety of cellular activities. These included macrophage adherence, cytoplasmic spreading and macrophage-macrophage membrane fusions to form foreign body giant cells. The foreign body giant cells exhibited nuclear reorganization and, when compared with adherent macrophages, they displayed an enhanced ability to fuse to neighbouring leucocytes, increased spreading of membrane processes over the polymer surface, the presence of large cytoplasmic vacuoles, and a lengthened duration of enzymatic activity. Contact angle analysis showed the Pellethane surfaces to be hydrophobic and of low hysteresis. The critical surface tension and the dispersive component of the total surface tension were found to increase with Pellethane hardness.

In vivo leucocyte interactions with the NHLBI-DTB primary reference materials: polyethylene and silica-free polydimethylsiloxane.

In vivo leucocyte interactions with the NHLBI-DTB primary reference materials, low density polyethylene (LDPE) and silica-free polydimethylsiloxane (PDMS), were qualitatively and quantitatively characterized using a cage implant system over a 21 d implantation period. Scanning electron microscopy (SEM) and cytochemical staining procedures were utilized to observe the cellular events occurring at the leucocyte/biomaterial interface. The results showed that more cells adhered to the PDMS surface than the LDPE surface at days 4 and 7. The differential analysis revealed that mononuclear cells, presumably macrophages, preferentially adhered to both polymer surfaces. By day 21, there were more very large (greater than 20 nuclei per cell) foreign body giant cells (FBGCs) present on the PDMS surface than the LDPE surface. The phagocytic capabilities of the adhered cells, including the FBGCs, decreased to a greater extent on the PDMS surface, corresponding to the earlier and more extensive spreading of these cells observed in the morphological analysis.