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. 2024 Mar 22:11:rbae027.
doi: 10.1093/rb/rbae027. eCollection 2024.

In vitro and in vivo degradation, biocompatibility and bone repair performance of strontium-doped montmorillonite coating on Mg-Ca alloy

Wenxin Sun  1 , Kaining Yang  1 , Yuhong Zou  1 , Yande Ren  2 , Lin Zhang  3 , Fen Zhang  4 , Rongchang Zeng  4
Affiliations

In vitro and in vivo degradation, biocompatibility and bone repair performance of strontium-doped montmorillonite coating on Mg-Ca alloy

Wenxin Sun et al. Regen Biomater. .

Abstract

Poor bone growth remains a challenge for degradable bone implants. Montmorillonite and strontium were selected as the carrier and bone growth promoting elements to prepare strontium-doped montmorillonite coating on Mg-Ca alloy. The surface morphology and composition were characterized by SEM, EDS, XPS, FT-IR and XRD. The hydrogen evolution experiment and electrochemical test results showed that the Mg-Ca alloy coated with Sr-MMT coating possessed optimal corrosion resistance performance. Furthermore, in vitro studies on cell activity, ALP activity, and cell morphology confirmed that Sr-MMT coating had satisfactory biocompatibility, which can significantly avail the proliferation, differentiation, and adhesion of osteoblasts. Moreover, the results of the 90-day implantation experiment in rats indicated that, the preparation of Sr-MMT coating effectively advanced the biocompatibility and bone repair performance of Mg-Ca alloy. In addition, The Osteogenic ability of Sr-MMT coating may be due to the combined effect of the precipitation of Si4+ and Sr2+ in Sr-MMT coating and the dissolution of Mg2+ and Ca2+ during the degradation of Mg-Ca alloy. By using coating technology, this study provides a late-model strategy for biodegradable Mg alloys with good corrosion resistance, biocompatibility. This new material will bring more possibilities in bone repair.

Keywords: Mg–Ca alloy; biocompatibility; corrosion resistance; montmorillonite; osteogenesis; strontium.

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Figures

None
Graphical abstract
Figure 1.
Figure 1.
(A) Preparation process of Sr-MMT coating. (B) Establishment of bone implantation model.
Figure 2.
Figure 2.
(A) SEM morphologies and the corresponding EDS spectra of (a1–a3) Na-MMT, and (b1–b3) Sr-MMT coating. (B) Mapping of the Na-MMT coating. (C) Mapping of the Sr-MMT coating.
Figure 3.
Figure 3.
(A and B) FT-IR Spectra and XRD patterns of the Sr/MMT coating, Sr-MMT powder, MMT coating and MMT powder. (C) XPS spectrum of Na-MMT coating (a) and typical peak-fitting results of the Na 1s (b). (D) XPS spectrum of Sr-MMT coating (a) and typical peak-fitting results of the Sr 3d (b). (E) Frictional force of the Sr-MMT coating.
Figure 4.
Figure 4.
(A) HER curves of Mg–Ca alloy, Na-MMT and Sr-MMT coatings immersed for 7 days. (B) Change in pH for Mg–Ca alloy, Na-MMT and Sr-MMT coatings in DMEM for 24 h. (C and D) FT-IR spectra and XRD patterns of the coatings immersed in DMEM for 7 days. (E) SEM images and EDS spectra of (a) Mg–Ca alloy, (b) Na-MMT coating and (c) Sr-MMT coating after soaking in DMEM solution for 7 days.
Figure 5.
Figure 5.
EIS And the fitted results for Mg–Ca alloy, Na-MMT and Sr-MMT coatings: (A) Nyquist plots; (B) Potentiodynamic polarization (PDP) curves; (C) Bode plots of phase angle vs frequency; (D) Bode plots of |Z| vs frequency in DMEM; (E) Equivalent circuits of the Mg–Ca alloy; (F) Equivalent circuits of the Na-MMT coating and Sr-MMT coating.
Figure 6.
Figure 6.
(A) Relative activity of MC3T3-E1 cells incubated for 24 h (a); images of live/dead staining incubated for 24 h (b1–b4) and 72 h (c1–c4) (*P ＜ 0.05). (B) Sr2+ and Si4+ release curve of Sr-MMT immersed in DMEM solution for 10 days. (C) Viability of ALP when Mg–Ca alloy, Na-MMT and Sr-MMT coatings were co-cultured with MC3T3-E1 cells for 72 h (a), CLSM shooting results (200×) after the sample was co-cultured with MC3T3-E1 cells for 24 h(b1–b4) and 72 h(c1–c4) (*P ＜ 0.05).
Figure 7.
Figure 7.
(A) X-ray films of rats implanted with bone screw for 1 day, 1 month and 3 months: Na-MMT group (a1–a3) and Sr-MMT group (b1–b3). (B) HE staining images after hard tissue section: Mg–Ca alloy (a1 and a2), Na-MMT coating (b1 and b2) and Sr-MMT coating (c1 and c2). black areas: implanted bone screw; purple areas: bone tissue; dark areas: bone tissue; yellow: marrow; red areas: new bone.
Figure 8.
Figure 8.
Mechanism of promoting bone formation.
See this image and copyright information in PMC

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