Greener synthesis of electrospun collagen/hydroxyapatite composite fibers with an excellent microstructure for bone tissue engineering

Figures & data

Figure 1 Characterization of HAP sol.

Notes: (A) Photograph of HAP precursor sol, (B) TEM micrograph of HAP nanoparticles.

Abbreviations: HAP, hydroxyapatite; TEM, transmission electron microscopy.

Figure 2 XRD pattern of HAP particles in sol.

Abbreviations: HAP, hydroxyapatite; XRD, X-ray diffraction.

Figure 3 The morphology of electrospun fibers with different HAP contents.

Notes: (A) 0%, (B) 10%, (C) 20%, (D) 30%, (E) 40%, and collagen/30% HAP control fibers (F), respectively.

Abbreviation: HAP, hydroxyapatite.

Figure 4 TEM images of the fibers and spinning solutions.

Notes: (A) Collagen fibers before desalination, (B) collagen/HAP before desalination, (C) collagen fibers after desalination, (D) collagen/HAP after desalination, (E) collagen/30% HAP spinning solution, (F) collagen/30% HAP fibers after desalination, (G) collagen/HAP spinning solution using HAP powders, (H) collagen/30% HAP control fibers.

Abbreviations: HAP, hydroxyapatite; TEM, transmission electron microscopy.

Figure 5 Schematic illustration of the proposed mechanism for the HAP particles oriented along the long axes of the collagen fiber.

Abbreviation: HAP, hydroxyapatite.

Figure 6 FTIR spectra.

Notes: (A) HAP, (B) collagen fibers, (C) collagen/HAP composite fibers.

Abbreviations: HAP, hydroxyapatite; FTIR, Fourier-transform infrared spectroscopy; au, arbitrary units.

Figure 7 XRD patterns of collagen fibers and collagen/HAP fibers.

Notes: (A) Collagen fibers before desalination, (B) collagen fibers after desalination, (C) collagen/30% HAP composite fibers.

Abbreviations: HAP, hydroxyapatite; XRD, X-ray diffraction.

Figure 8 SEM photographs of the electrospun fibers after cross-linking with EDC/NHS.

Notes: (A) Collagen fibers, (B) collagen/10% HAP fibers, (C) collagen/30% HAP fibers.

Abbreviations: HAP, hydroxyapatite; SEM, scanning electron microscope; EDC/NHS, 1-ethyl-3-(3-dimethyl-aminopropyl)-1-carbodiimide hydrochloride/N-hydroxysuccinimide.

Table 1 Mechanical properties of collagen and collagen/HAP composite fibers with different content of HAP

No	HAP contents (%)	Peak force (CN)	Tensile strength (MPa)	Percentage of elongation (%)	Cross-linked or not
1	0*	9.8±0.18	72±0.23	26.4±0.17	No
2	0	10.9±0.32	74±0.31	36.3±1.98	No
3	10	13.2±0.17	87±0.20	77.2±0.42	No
4	20	15.4±0.23	119±0.21	76.5±0.31	No
5	20	17.2±0.16	144±0.14	64±0.23	Yes
6	30	20.8±0.11	147±0.12	72.3±1.48	No
7	30	22.3±0.09	209±0.16	58±0.18	Yes
8	40	7.6±0.15	124±0.14	23.5±0.21	No
9	40	7.4±0.17	168±0.11	18.5±0.21	Yes
10	30**	7.0±0.08	76±0.09	16.5±0.13	No

Notes:

* Notes: Without desalination,

** control sample.

Abbreviation: HAP, hydroxyapatite.

Figure 9 Viability of U2-OS cells in leaching liquors of collagen and collagen/HAP composite nanofibers after culture for 1, 3, 5, and 7 days.

Abbreviations: HAP, hydroxyapatite; PTFE, polytetrafluoroethylene; d, day(s).

Figure 10 ALP activity of U2-OS cells after being cultured for 1, 2, 3, 4, 5, 6, and 7 days in medium containing material extraction.

Abbreviations: HAP, hydroxyapatite; PTFE, polytetrafluoroethylene; d, day(s).