Resazurin reduction assay on HUVECs in two-dimensional culture. (A) Fluorescence readings of resazurin reduction assay on serial dilutions of HUVECs (cell number to medium ratio of 1, 0.5, 0.25, 0.1, 0.05, 0.025 and 0.01 million/ml) in 2 ml and 0.1 ml volume formats. (B) Growth curve of HUVECs cultured in T75 flasks calculated from resazurin reduction assays according to the standard curve. Assays were performed on day 0 (6 hours after cell seeding), day 1, day 2 and day 3. Two groups of assays were performed with an initial seeding number of 0.5 and 1 million HUVECs per T75 flask. (C) Fold changes in HUVEC numbers over the 3 days of two-dimensional culture revealed by resazurin reduction assays and cell counting. Data were presented as means with standard deviations (n=3 for each experimental arm).