Changes in physicochemical and biological properties of porcine bone derived hydroxyapatite induced by the incorporation of fluoride

Figures & data

Figure 1. TEM images (scale bar = 100 nm) and magnified section (scale bar = 5 nm) with corresponding SAED patterns (scale bar = 5 1/nm) of (a, e) PHAp; (b, f) 0.25-FPHAp; (c, g) 0.50-FPHAp; (d, h) 0.75-FPHAp. SEM images (scale bar = 1 μm) of (i) PHAp; (j) 0.25-FPHAp; (k) 0.50-FPHAp; (l) 0.75-FPHAp. EDS spectra, as well as the distribution of calcium and fluoride by EDS mapping of (m) PHAp; (n) 0.25-FPHAp; (o) 0.50-FPHAp; (p) 0.75-FPHAp.

Table 1. Elemental analysis of PHAp and FPHAp samples by EDS.

	Atomic percentage (wt. %)
	Ca	P	O	C	Na	Mg	F
PHAp	44.6 ± 0.4	20.6 ± 0.3	27.8 ± 0.4	3.3 ± 0.7	1.3 ± 0.5	1.8 ± 0.2	0.6 ± 0.9
0.25-FPHAp	42.5 ± 0.1	19.4 ± 0.4	27.6 ± 0.8	3.6 ± 0.3	2.0 ± 0.3	1.4 ± 0.1	3.5 ± 0.1
0.50-FPHAp	43.9 ± 0.1	19.2 ± 0.1	26.1 ± 0.3	3.4 ± 0.2	2.1 ± 0.1	1.10 ± 0.02	4.2 ± 0.1
0.75-FPHAp	40 ± 2	18.8 ± 0.1	24.3 ± 0.6	3.3 ± 0.1	4.3 ± 2.2	1.8 ± 0.3	7.2 ± 0.6

Figure 2. (a) FTIR spectra, (b) expanded water stretching region and (c) OH libration region of PHAp, 0.25-FPHAp, 0.50-FPHAp, and 0.75-FPHAp. (d) XRD patterns and (e) expanded X-ray reflections of PHAp, 0.25-FPHAp, 0.50-FPHAp, and 0.75-FPHAp (all spectra are vertically offset for clarity).

Table 2. Lattice constants and crystallinity of PHAp, 0.25-FPHAp, 0.50-FPHAp, and 0.75-FPHAp. With the rise in fluoride content, the crystallinity of the apatite steadily increased. The incorporation of fluoride also resulted in significant decline of a lattice constant of the apatite, while the c lattice constant did not show any discernable difference.

	Lattice constant (Å)		Crystallinity(%)
	a-axis	c-axis
PHAp	9.42541	6.88685	94.4 ± 1.6
0.25-FPHAp	9.40576	6.88174	96.9 ± 2.2
0.50-FPHAp	9.38676	6.88120	98.7 ± 2.2
0.75-FPHAp	9.38234	6.88467	98.7 ± 1.4

Figure 3. Box plot showing the compressive strength of PHAp, 0.25-FPHAp, 0.50-FPHAp, and 0.75-FPHAp.

Figure 4. (a) Mercury intrusion cumulative curves of PHAp, 0.25-FPHAp, 0.50-FPHAp, and 0.75-FPHAp. (b) Incremental intrusion in relate to pore diameter showing the pore diameter distribution of PHAp, 0.25-FPHAp, 0.50-FPHAp, and 0.75-FPHAp.

Figure 5. Solubility isotherms of PHAp, 0.25-FPHAp, 0.50-FPHAp, and 0.75-FPHAp 100 mM KCl solution at 37.0 ± 0.1°C by solid titration. Solubility data of stoichiometric HAp were shown for comparison.

Figure 6. SEM images (scale bar = 20 μm) and inserted magnified view (scale bar = 10 μm) showing the adhesion of human osteoblastic-like MG63 cell on the surfaces of (a) PHAp, (b) 0.25-FPHAp, (c) 0.50-FPHAp, and (d) 0.75-FPHAp. (e) Quantitative evaluation of cell attachment showed only 0.25-FPHAp favored increased attachment of MG63, while 0.75-FPHAp was inferior than PHAp for cell attachment. (f) Protein absorption assay demonstrated that the incorporation of fluoride resulted in significant higher protein absorption of the apatite.