Figure 3. Hardness and elastic modulus of the day 24 osteoblastic mineralized tissue obtained from nano-indentation. The mineralized tissue was formed after culture on either the polystyrene, the machined titanium, or the acid-etched titanium surface. From days 21 to 24, the mineralized tissues were treated with the following glycosaminoglycan (GAG) degrading enzyme: ChAC (chondroitinase AC); ChB (chondroitinase B); He (heparinase); Ke (keratanase). Control: untreated control culture. Data are shown as the mean ± SD (n = 9).