The preparation of a difunctional porous β-tricalcium phosphate scaffold with excellent compressive strength and antibacterial properties

Abstract

Porous β-tricalcium phosphate (β-Ca₃(PO₄)₂, β-TCP) scaffolds are widely applied in the field of bone tissue engineering due to their nontoxicity, degradability, biocompatibility, and osteoinductivity. However, poor compressive strength and a lack of antibacterial properties have hindered their clinical application. In order to address these disadvantages, graphene (G) and silver nanoparticles were introduced into β-TCP through a two-step method. In the synthesis process, G-β-TCP was prepared via an in situ synthesis method, and then silver nanoparticles and HAp particles were coated on the surface of the G-β-TCP scaffold in an orderly fashion using dopamine as a binder. From the results of characterization, when the content of graphene was 1 wt% of β-TCP, the G-β-TCP scaffold had the highest compression strength (127.25 MPa). And core-shell G-β-TCP-Ag-HAp not only had reduced cytotoxicity via the continuous release of Ag⁺, but it also achieved long-term antibacterial properties. Besides, the material still showed good cell activity and proliferation.

Fig. 1. The preparation process diagram of G-β-TCP-Ag-HAp.

Fig. 2. XRD patterns of β-TCP and x wt% G-β-TCP.

Fig. 3. Raman spectra of graphene and x wt% G-β-TCP.

Fig. 4. TEM images of the prepared materials: pure graphene (a), and 0.2 wt% (b), 0.5 wt% (c), 1 wt% (d), 1.5 wt% (e), and 2 wt% G-β-TCP (f).

Fig. 5. Micrographs of the prepared materials: pure β-TCP (a), 0.2 wt% graphene-β-TCP (b), 0.5 wt% graphene-β-TCP (c), 1 wt% graphene-β-TCP (d), 1.5 wt% graphene-β-TCP (e), and 2 wt% graphene-β-TCP (f).

Fig. 6. The open porosity and density properties of x wt% G-β-TCP.

Fig. 7. The remaining amount of graphene.

Fig. 8. Stress–strain curves of specimens.

Fig. 9. SEM images of G-β-TCP-Ag (a), G-β-TCP-Ag-pDA (b), and G-β-TCP-Ag-HAp (c), and the EDS spectrum of G-β-TCP-Ag-HAp (d).

Fig. 10. TEM images of samples: G-β-TCP-Ag (a) and G-β-TCP-Ag-HAp (b); the insets show the selected area electron diffraction patterns of the corresponding samples.

Fig. 11. Growth inhibition zones of G-β-TCP, G-β-TCP-Ag, and G-β-TCP-Ag-HAp against S. aureus (a) and E. coli (b).

Fig. 12. Photos showing the growth of E. coli (a–c) and S. aureus (d–f) on LB agar plates after 24 hours of incubation. The bacteria reacted with G-β-TCP (a and d), G-β-TCP-Ag (b and e), and G-β-TCP-Ag-HAp (c and f) in a liquid LB medium for 24 hours before testing.

Fig. 13. Optical density values illustrating MG63 cell proliferation on G-β-TCP, G-β-TCP-Ag, and G-β-TCP-Ag-HAp scaffolds after culturing for 1, 3, and 5 days. Each value is the mean ± standard error from three observations. * represents p < 0.05 between groups on the same day.