In cell attachment test, the MG-63 osteoblast-like cells were seeded in density of 3.6 × 105 cells/40 μl for each specimen. After cell seeding, they were incubated for 2 h and then added in immersed culture medium. At each time point (4, 8, 12 and 24 h), specimens were moved to new 24-well plates and washed two times with PBS solution. The attachment rate was measured by using cell counting kit-8 (CCK-8, Sigma-Aldrich) by absorbing read on a micro-plate reader at 450 nm.