Preparation and characterization of different micro/nano structures on the surface of bredigite scaffolds

Abstract

The preparation of controllable micro/nano structures on the surface of the bredigite scaffold is expected to exhibit the same support and osteoconductive capabilities as living bone. However, the hydrophobicity of the white calciμm silicate scaffold surface restricts the adhesion and spreading of osteoblasts. Furthermore, during the degradation process of the bredigite scaffold, the release of Ca²⁺ results in an alkaline environment around the scaffold, which inhibits the growth of osteoblasts. In this study, the three-dimensional geometry of the Primitive surface in the three-periodic minimal surface with an average curvature of 0 was used as the basis for the scaffold unit cell, and a white hydroxyapatite scaffold was fabricated via photopolymerization-based 3D printing. Nanoparticles, microparticles, and micro-sheet structures with thicknesses of 6 μm, 24 μm, and 42 μm, respectively, were prepared on the surface of the porous scaffold through a hydrothermal reaction. The results of the study indicate that the micro/nano surface did not affect the morphology and mineralization ability of the macroporous scaffold. However, the transition from hydrophobic to hydrophilic resulted in a rougher surface and an increase in compressive strength from 45 to 59-86 MPa, while the adhesion of the micro/nano structures enhanced the scaffold's ductility. In addition, after 8 days of degradation, the pH of the degradation solution decreased from 8.6 to around 7.6, which is more suitable for cell growth in the hμman body. However, there were issues of slow degradation and high P element concentration in the degradation solution for the microscale layer group during the degradation process, so the nanoparticle and microparticle group scaffolds could provide effective support and a suitable environment for bone tissue repair.

Figure 1

Design process of scaffold model. (a) single-cell curved surface, (b) single-cell curved surface model, (c) single-cell solid model and (d) TPMS bone scaffold model.

Figure 2

Sintering temperature profile of adhesive, ① Room temperature ~ 200 °C, heating rate: 2 °C /min, heat preservation for 30 min; ② 200–300 °C, heating rate: 0.5 °C/min, holding time 2 h; ③ 300–400 °C, 0.25 °C /min, holding time 1 h; ④ 400–600 °C, heating rate of 1 °C /min, heat preservation time of 1 h; ⑤ 600–1300 °C, heating rate 4 °C/min, holding time 4 h; ⑥ Free cooling to room temperature.

Figure 3

Optical images and porosity estimation of the scaffold. (a) Control group, (b) nanoparticle group, (c) microparticle group, (d) micro-sheet group.

Figure 4

SEM micrographs for surface morphology and thickness of scaffolds (a) control group, (b) nanoparticle group, (c) microparticle group, (d) micro-sheet group.

Figure 5

SEM micrographs and the corresponding EDS spectra of the scaffolds (a,b) the control group scaffolds, (c,d) the micro-sheet group scaffolds.

Figure 6

XRD patterns of blank surface and micro/nano structured materials are compared with standard cards. (a) Is the comparison between the scaffold of control group and the standard card of bredigite, and (b) is the comparison between the scaffold of micro-sheet group and the standard card of β-tricalciμm phosphate.

Figure 7

Water contact angle of the scaffold. (a) Control group, (b) nanoparticle group, (c) microparticle group, (d) micro-sheet group.

Figure 8

Surface roughness of scaffolds.

Figure 9

Stress–strain curves of scaffolds.

Figure 10

(a) the Quality change of scaffolds, (b) the compressive strength of scaffolds, (c) PH changes of scaffolds.

Figure 11

SEM micrographs for surface of the (a1) control group, (a2) nanoparticle group, (a3) microparticle group, (a4) micro-sheet group. (b) Concentration of Ca, Mg, Si and P element in the four groups of SBF at 2w. FTIR spectra of different micro/nano structured scaffolds before and after 7 days of degradation.

Figure 12

Formation process of micro/nano structure Ca-P surface.