Hierarchically nanostructured hydroxyapatite: hydrothermal synthesis, morphology control, growth mechanism, and biological activity

Figures & data

Table 1 Detailed experimental parameters for the synthesis of some typical samples by hydrothermal method

Sample	Temperature	Time	Reaction system
1	200°C	24 hours	0.001 mol CaCl2 + 0.001 mol C4H4O6KNa · 4H2O + 0.0006 mol NaH2PO4 + 15 mL water
2	200°C	12 hours	0.001 mol CaCl2 + 0.001 mol C4H4O6KNa · 4H2O + 0.0006 mol NaH2PO4 + 15 mL water
3	200°C	3 hours	0.001 mol CaCl2 + 0.001 mol C4H4O6KNa · 4H2O + 0.0006 mol NaH2PO4 + 15 mL water
4	200°C	4 hours	0.001 mol CaCl2 + 0.001 mol C4H4O6KNa · 4H2O + 0.0006 mol NaH2PO4 + 15 mL water
5	200°C	6 hours	0.001 mol CaCl2 + 0.001 mol C4H4O6KNa · 4H2O + 0.0006 mol NaH2PO4 + 15 mL water
6	160°C	24 hours	0.001 mol CaCl2 + 0.001 mol C4H4O6KNa · 4H2O + 0.0006 mol NaH2PO4 + 15 mL water
7	200°C	24 hours	0.001 mol CaCl2 + 0.0006 mol NaH2PO4 + 15 mL water
8	Room temperature	30 minutes	0.001 mol CaCl2 + 0.001 mol C4H4O6KNa · 4H2O + 15 mL water
9	200°C	24 hours	0.001 mol CaCl2 + 0.001 mol C4H4O6 KNa·4H2O + 15 mL water

Figure 1 Field emission scanning electron microscopy images of hierarchically nanostructured hydroxyapatite (sample 1).

Figure 2 TEM images of hierarchically nanostructured hydroxyapatite (sample 1): (A and B) the edges of the flower-like assembly; (C) the edges of the nanosheets; (D) an individual nanorod; (E) the corresponding high-resolution TEM micrograph of (D); and (F) the nanorod after exposure to electron beam irradiation. The inset of (D) shows the corresponding selected area electron diffraction pattern.

Abbreviation: TEM, transmission electron microscopy.

Figure 3 A typical XRD pattern (A) and FTIR spectrum (C) of hydroxyapatite powders prepared by hydrothermal method at 200°C for 24 hours; XRD pattern (B) and FTIR spectrum (D) of the sample prepared by calcination of (A) at 800°C for 3 hours.

Abbreviations: FTIR, Fourier transform infrared; XRD, X-ray powder diffraction.

Figure 4 Energy-dispersive X-ray analysis spectrum of hierarchically nanostructured hydroxyapatite (sample 1).

Figure 5 X-ray powder diffraction patterns of hierarchically nanostructured hydroxyapatite prepared by hydrothermal method at 200°C for different lengths of time: 3 hours (sample 3) (A); 4 hours (sample 4) (B); 6 hours (sample 5) (C); and 12 hours (sample 2) (D).

Figure 6 Scanning electron microscopy images of hierarchically nanostructured hydroxyapatite prepared by hydrothermal method at 200°C for 12 hours (sample 2).

Figure 7 Scanning electron microscopy images of hierarchically nanostructured hydroxyapatite prepared by hydrothermal method at 200°C for different lengths of time: (A) 3 hours (sample 3); (B) 4 hours (sample 4); (C) 6 hours (sample 5).

Figure 8 Scanning electron microscopy images of hierarchically nanostructured hydroxyapatite prepared by hydrothermal method at 160°C for 24 hours (sample 6).

Figure 9 Schematic representation of the formation mechanism of hierarchically nanostructured HA.

Abbreviation: HA, hydroxyapatite.

Figure 10 Scanning electron microscopy images of (A–C) the sample synthesized by using CaCl₂ and NaH₂PO₄ without the addition of C₄H₄O₆ KNa · 4H₂O at 200°C for 24 hours (sample 7); (D–F) the sample synthesized by using CaCl₂ and C₄H₄O₆ KNa · 4H₂O at room temperature for 30 minutes (sample 8); and (G–I) the sample synthesized by using CaCl₂ and C₄H₄O₆ KNa · 4H₂O at 200°C for 24 hours (sample 9).

Figure 11 Viability of normal human fibroblasts incubated with hierarchically nanostructured hydroxyapatite at different concentrations.

Notes: They were determined by counting the survival cells per well in comparison with untreated cells. The error bars denote standard deviations.