Apatite Coating of Scaffold Discs

Apatite coating solution was prepared as described in previous studies [31 (link), 32 (link)]. Briefly, simulated body fluids (SBF) were formulated by sequentially dissolving CaCl₂, MgCl₂·6H₂O, NaHCO₃, and K₂HPO₄·3H₂O into ddH₂O. Adjustment of pH was made to 6.0, and then Na₂SO₄, KCl, and NaCl were dissolved. The final solution was brought to a pH of 6.5 (SBF1). Mg²⁺ and HCO₃⁻ free SBF (SBF2) was prepared by similarly dissolving CaCl₂ and K₂HPO₄·3H₂O into ddH₂O and pH was adjusted to 6.0. KCl and NaCl were added, and the solution was adjusted to pH 6.8. All solutions were sterile filtered by using a 0.22-µm polyethersulfone membrane (Nalgene, Rochester, NY, http://nalgene.com). The scaffold discs were subjected to glow discharge argon plasma etching (Harrick Scientific, Pleasantville, NY, http://www.harricksci.com). The etched scaffolds were immersed and incubated in SBF1 for 24 hours and then further incubated in SBF2 for another 24 hours at 37°C. The apatite-coated scaffolds were washed with sterile ddH₂O to remove excess ions and lyophilized before further studies.