Figure 2. Systematic change of mineral coating crystallinity and its effect on mineral stability.

(a) FTIR spectra of CaP mineral coatings. The peaks are associated with the PO₄³⁻ (…) and CO₃²⁻ (− −) groups. (b) The effect of mSBF solution characteristics on resulting mineral crystallinity index, which was calculated using FTIR analysis (Supplementary Fig. S1). (c) Ca/P ratio of mineral coatings. * indicates significant difference when compared with Ca/P ratio of CaP mineral coating grown in 2 × mSBF with 4.2 mM of CO₃²⁻ (red bar at far left) by Student's t-test with p < 0.05. Data represents mean ± SD (n = 3). (d) Dissolution of mineral coatings formed in 12 different mSBF solutions. The change of Ca²⁺ amount in cell culture medium was measured at different time points. Data represents mean ± SD (n = 4). (e) The effect of relative crystallinity on mineral stability. The released Ca²⁺ amount after 2 days incubation in cell culture medium is plotted in terms of crystallinity index of mineral coatings. Data represents mean ± SD (n = 4).