Adhesion and proliferation of rat vascular smooth muscle cells (VSMC) on polyethylene implanted with O+ and C+ ions

Polyethylene was implanted with 30-keV oxygen (PE/O+) or 23-keV carbon ions (PE/C+) at 1013 to 5 × 1015 ions cm-2 doses in order to improve the adhesion of vascular smooth muscle cell (VSMC) to the polymer surface in vitro because of its oxidation and carbon-enrichment. The concentration of-CO- groups in the PE/O+ and PE/C+ samples increased only up to doses of 3 × 1014 and 1015 ions cm-2, respectively, and then declined. At the same time, the concentration of these groups, measured at a dose of 3 × 1014 ions cm-2, was higher in PE/O+ than in PE/C+ samples. Similarly, the number of initially-adhering rat VSMC (24 h after seeding) increased only up to a dose of 3 × 1013 and 1015 ions cm-2 on PE/O+ and PE/C+ samples, respectively. In addition, between doses of 1013 and 1014 ions cm-2, this number was about two to three times higher on PE/O+ samples. On the other hand, the surface wettability increased proportionally to the implanted ion dose, especially above a dose of 1014 ions cm-2. Thus, the number of initiallyadhered cells appeared to be positively correlated with the amount of the oxygen group present at the polymer surface rather than with the surface wettability. The higher cell adhesion was accompanied by adsorption of fluorescent dye-conjugated collagen IV in larger amounts. The highest numbers of initially-adhered cells were usually associated with the lowest rates of subsequent proliferation (measured by the doubling time, BrdU labelling and MTT reduction assay) and the largest cell volumes. These results indicate that: (1) implantation of O+ and C+ ions significantly improved initial adhesion of VSMC to polyethylene; (2) this effect was more pronounced in O+ irradiated samples, especially at a dose of 3 × 1013 ions cm-2; and (3) the latter sample seemed to be most suitable for tissue engineering where high initial densities, low subsequent proliferation, and high differentiation are desirable, e.g. for vascular prostheses.