Fig. 1.
Design of doughnut-hole dish and overview of the co-culture assay. a A schema of our original co-culture dish: doughnut-hole dish, a glass bottom dish which contains two isolated holes surrounded by polydimethylsiloxane (PDMS) walls. b Photo of the doughnut-hole dish. c Schema of doughnut-hole dish assay for co-culturing human umbilical vein endothelial cells (HUVECs) and a glioblastoma (GBM) cell line. HUVECs (5 × 106 cells/ml) suspended in fibrin-collagen gel (150 μl) were filled inside the doughnut-holes (red colored area), and GBM cells (5 × 106 cells/ml) suspended in fibrin-collagen gel (40 μl) were added to the marginal area (green color); then, medium (1 ml) (orange color) was poured to cover the whole area