Modification of expanded polytetrafluoroethylene surface with low-energy nitrogen-ion-beam irradiation

Even though improvement of expanded polytetrafluoroethylene (ePTFE) vascular graft patency has been tried by tissue engineering via surface modification, its results are less than initially hoped for. To increase both initial cell adhesion and the interaction between regenerating tissue and the non-biodegradable ePTFE surface in our hybrid graft system, we performed and evaluated surface modification of the ePTFE after predetermining the irradiation conditions with Stopping and Range of Ions in Matter software by irradiating the surfaces of ePTFE with low-energy nitrogen-ion beams. The extent of surface modification of ePTFE was investigated by employing irradiation its surface with nitrogen-ion beams of 1 to 50 keV at a density of 1 × 10¹⁵ ions/cm². While its morphological and color changes was observed with a scanning electron microscope and a digital image camera, respectively, chemical composition changes were observed with X-ray photoelectron microscopy. In vitro cell culture was further performed on the ePTFE surface, and changes in cell populations were evaluated, with a cell counting kit, by detecting the optical density of the medium with microplatereader. The cellular interactions were slightly increased on the surfaces of nitrogen ion beam-treated ePTFE, but significant increases on the PTFE films depend on the beam energies.