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. 2020 Sep 10;6(2):490-502.
doi: 10.1016/j.bioactmat.2020.09.001. eCollection 2021 Feb.

Accelerated degradation of HAP/PLLA bone scaffold by PGA blending facilitates bioactivity and osteoconductivity

Cijun Shuai  1   2   3 , Wenjing Yang  1   2 , Pei Feng  1 , Shuping Peng  4   5 , Hao Pan  6
Affiliations

Accelerated degradation of HAP/PLLA bone scaffold by PGA blending facilitates bioactivity and osteoconductivity

Cijun Shuai et al. Bioact Mater. .

Abstract

The incorporation of hydroxyapatite (HAP) into poly-l-lactic acid (PLLA) matrix serving as bone scaffold is expected to exhibit bioactivity and osteoconductivity to those of the living bone. While too low degradation rate of HAP/PLLA scaffold hinders the activity because the embedded HAP in the PLLA matrix is difficult to contact and exchange ions with body fluid. In this study, biodegradable polymer poly (glycolic acid) (PGA) was blended into the HAP/PLLA scaffold fabricated by laser 3D printing to accelerate the degradation. The results indicated that the incorporation of PGA enhanced the degradation rate of scaffold as indicated by the weight loss increasing from 3.3% to 25.0% after immersion for 28 days, owing to the degradation of high hydrophilic PGA and the subsequent accelerated hydrolysis of PLLA chains. Moreover, a lot of pores produced by the degradation of the scaffold promoted the exposure of HAP from the matrix, which not only activated the deposition of bone like apatite on scaffold but also accelerated apatite growth. Cytocompatibility tests exhibited a good osteoblast adhesion, spreading and proliferation, suggesting the scaffold provided a suitable environment for cell cultivation. Furthermore, the scaffold displayed excellent bone defect repair capacity with the formation of abundant new bone tissue and blood vessel tissue, and both ends of defect region were bridged after 8 weeks of implantation.

Keywords: Bone regeneration; Degradation; HAP/PLLA; PGA; Scaffold.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Image 1
Graphical abstract
Fig. 1
Fig. 1
(a) Raw powder of PLLA, PGA and HAP, (b) SEM micrographs and the corresponding EDS elemental mapping images of the prepared PLLA/HAP, 1PLLA/1PGA/HAP and PGA/HAP composite powder, (c) Typical optical images of the PLLA/HAP, 1PLLA/1PGA/HAP and PGA/HAP scaffolds seen from the top.
Fig. 2
Fig. 2
(a) XRD patterns, (b) FTIR spectra, (c) DSC and (d) TGA curves of the composite scaffolds. 1# represents the PLLA/HAP scaffold, 2# represents the 3PLLA/1PGA/HAP scaffold, 3# represents the 1PLLA/1PGA/HAP scaffold, 4# represents the 1PLLA/3PGA/HAP scaffold, 5# represents the PGA/HAP scaffold.
Fig. 3
Fig. 3
(a) The typical stress-strain curves, (b) Compressive strength and modulus of the composite scaffolds (*P < 0.05 and **P < 0.01). 1# represents the PLLA/HAP scaffold, 2# represents the 3PLLA/1PGA/HAP scaffold, 3# represents the 1PLLA/1PGA/HAP scaffold, 4# represents the 1PLLA/3PGA/HAP scaffold, 5# represents the PGA/HAP scaffold. Data were presented as mean ± standard deviation.
Fig. 4
Fig. 4
SEM micrographs for fracture surface of the (a) PLLA/HAP scaffold, (b) 3PLLA/1PGA/HAP scaffold, (c) 1PLLA/1PGA/HAP scaffold, (d) 1PLLA/3PGA/HAP scaffold, (e) PGA/HAP scaffold.
Fig. 5
Fig. 5
(a) Water absorption and (b) water contact angle of the scaffolds (**P < 0.01), (c) Weight loss of the scaffolds and (d) pH of the solution. 1# represents the PLLA/HAP scaffold, 2# represents the 3PLLA/1PGA/HAP scaffold, 3# represents the 1PLLA/1PGA/HAP scaffold, 4# represents the 1PLLA/3PGA/HAP scaffold, 5# represents the PGA/HAP scaffold. Data were presented as mean ± standard deviation.
Fig. 6
Fig. 6
SEM micrographs of surface morphologies of the 1PLLA/1PGA/HAP scaffold (a) before PBS immersion and (b–f) after PBS immersion for 28 d, (b) the PLLA/HAP scaffold, (c) the 3PLLA/1PGA/HAP scaffold, (d) the 1PLLA/1PGA/HAP scaffold, (e) the 1PLLA/3PGA/HAP scaffold, (f) the PGA/HAP scaffold.
Fig. 7
Fig. 7
SEM micrographs and the corresponding EDS spectra of the scaffolds (magnification × 2000, × 5000) incubated in SBF solution for 28 d (a1, a2, a3) the PLLA/HAP scaffold, (b1, b2, b3) the 3PLLA/1PGA/HAP scaffold, (c1, c2, c3) the 1PLLA/1PGA/HAP scaffold, (d1, d2, d3) the 1PLLA/3PGA/HAP scaffold, (e1, e2, e3) the PGA/HAP scaffold.
Fig. 8
Fig. 8
Fluorescence images of cell skeletons on the 1PLLA/1PGA/HAP scaffold for (a1) 1 d, (a2) 3 d, (a3) 5 d and (a4) 7 d, SEM micrographs of cell morphology on the 1PLLA/1PGA/HAP scaffold for (b1) 1 d, (b2) 3 d, (b3) 5 d and (b4) 7 d, (c) Proliferation of cells on the 1PLLA/1PGA/HAP scaffold for different times (**P < 0.01). Data were presented as mean ± standard deviation.
Fig. 9
Fig. 9
X-ray radiographs and micro-CT images of the 1PLLA/1PGA/HAP scaffold, PLLA/HAP scaffold and blank group after 4 and 8 weeks implantation. HE and MT images, bone volume fraction and bone mineral density of the 1PLLA/1PGA/HAP scaffold after 4 and 8 weeks implantation (**P < 0.01). Data were presented as mean ± standard deviation.
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