Fig. 4.
Modified surfaces significantly enhanced endothelial cell tubule formation. (A) HUVECs seeded onto modified surfaces exhibited extensive tubule formation (arrows) as early as 18 days, compared with the cobblestone appearance of HUVECs seeded on surfaces with only PEG–RGDS (B). (C) A significant increase in tubule formation on surfaces with covalently immobilized PDGF-BB (*P < 0.01) and surfaces with both covalently immobilized PDGF-BB and FGF-2 (#P < 0.05) can be seen compared with surfaces modified with PEG–RGDS alone.