Primary mature bovine chondrocytes on 4-terminated and unmodified SiO2 surfaces. (A) Normalized cell count, all data are normalized to the 4 hr count on unmodified SiO2. Data are reported as average ± 1 S.E. (n ≥ 16). Images, 20x, of chondrocytes stained with rhodamine phalloidin (red) and DAPI (blue) on (B) unmodified SiO2 after 4 hr, (C) 4-terminated SiO2 after 4 hr, (D) unmodified SiO2 after 24 hr, and (E) 4-modified SiO2 after 24 hr.(*) denotes statistical difference from the 4 hr control and (**) denotes statistical difference from the 24 hr control; scale bars = 100 μm.