Monocyte adhesion and adhesion molecule expression on human endothelial cells on plasma-treated PET and PTFE in vitro

The aim of this study was to evaluate in vitro the inflammatory potential of endothelialized surfaces of polyethylene terephthalate (PET) and polytetrafluorethylene (PTFE) after ammonia gas plasma modification. HUVECs grown on polystyrene and HUVECs stimulated with tumor necrosis factor (TNF-alpha) were used as controls. At day 1 and day 7, surfaces were evaluated for U937 cells and HUVECs using flow cytometry and immunohistochemistry. Plasma-treated PET (T-PET) and treated PTFE (T-PTFE) increased U937 cell adhesion compared to the negative control but this was not statistically significant. Maximal adhesion of U937 cells to HUVEC was observed on TNF-alpha stimulated endothelium with significant differences between day 1 and day 7. There was a small increase in U937 cell adhesion to plasma-treated PET compared to PTFE on both day 1 and day 7, but this was not statistically significant. Immunohistochemical staining demonstrated two patterns of distribution for monocyte adhesion on materials. On T-PET the cells were positioned in clusters attached to HUVECs and on T-PTFE the cells were randomly distributed on HUVECs and material. The effects of plasma-treated PET and PTFE on HUVEC adhesion and proliferation were also studied. On day 1 there were slight increases in the growth of HUVECs on both of T-PET and T-PTFE but this was not statistically significant. On day 7, cell number increased significantly on all of surfaces compared to the negative control. The results demonstrate that the plasma treatment of PET and PTFE with ammonia improves the adhesion and growth of endothelial cells and these surfaces do not exhibit a direct inflammatory effect in terms of monocyte adhesion. Plasma-treated PTFE enhances HUVECs growth and was less adhesive for monocytes as compared with treated PET. The monocyte adhesion to endothelial cells on surfaces can be used as a tool for the evaluation of material surface modification and further to study the mechanisms of cell to cell interactions in response to surfaces.