*2.2. Preparation of the Mineralizing Solution*

A metastable calcium phosphate solution was used in this study [12]. The composition of the solution is shown in Table 1. The Ca/P molar ratio of the mineralizing solution was 1.67, and it also contained 10 mM HEPES (*N*-2-Hydroxyethylpiperazine-*N* -2-Ethanesulfonic acid) KOH (potassium hydroxide) for buffering at pH 7.4. The final ionic strength of this solution was adjusted to 0.16 by adding 150 mM KCl (potassium chloride). The preparation of the solution was completed by dissolving reagent grade CaCl2 (calcium chloride), KH2PO4 (potassium phosphate), KCl (potassium chloride), and HEPES (*N*-2-Hydroxyethylpiperazine-*N* -2-Ethanesulfonic acid) into deionized distilled water. The degree of supersaturation with respect to hydroxyapatite was 3.85 × <sup>10</sup><sup>7</sup> at 37 ◦C.


**Table 1.** Composition of the mineralizing solution.
