Advanced bredigite-containing magnesium-matrix composites for biodegradable bone implant applications

Our plain-English summary of Advanced bredigite-containing magnesium-matrix composites for biodegradable bone implant applications, by S.N. Dezfuli, Z. Huan, A. Mol, et al (Materials Science & Engineering. C, Materials for Biological Applications, 2017).

The study

• Authors: S.N. Dezfuli, Z. Huan, A. Mol, S. Leeflang, J. Chang, J. Zhou
• Journal: Materials Science & Engineering. C, Materials for Biological Applications
• Published: 2017;79:647-660
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The present research was aimed at developing magnesium-matrix composites that could allow effective control over their physiochemical and mechanical responses when in contact with physiological solutions. A biodegradable, bioactive ceramic - bredigite was chosen as the reinforcing phase in the composites, based on the hypothesis that the silicon- and magnesium-containing ceramic could protect magnesium from fast corrosion and at the same time stimulate cell proliferation. Methods to prepare composites with integrated microstructures - a prerequisite to achieve controlled biodegradation were developed. A systematic experimental approach was taken in order to elucidate the in vitro biodegradation mechanisms and kinetics of the composites. It was found that the composites with 20-40% homogenously dispersed bredigite particles, prepared from powders, could indeed significantly decrease the degradation rate of magnesium by up to 24 times. Slow degradation of the composites resulted in the retention of the mechanical integrity of the composites within the strength range of cortical bone after 12days of immersion in a cell culture medium. Cell attachment, cytotoxicity and bioactivity tests confirmed the stimulatory effects of bredigite embedded in the composites on the attachment, viability and differentiation of bone marrow stromal cells. Thus, the multiple benefits of adding bredigite to magnesium in enhancing degradation behavior, mechanical properties, biocompatibility and bioactivity were obtained. The results from this research showed the excellent potential of the bredigite-containing composites for bone implant applications, thus warranting further in vitro and in vivo research.

Copyright © 2017 Elsevier B.V. All rights reserved.

In plain English

This laboratory study, which does not concern asbestos, tested whether adding bredigite, a calcium-magnesium-silicate ceramic, could slow the breakdown of magnesium meant for dissolving bone implants. The authors made pure magnesium and composites containing 20% and 40% bredigite by volume from powders, using pressure-assisted sintering. Samples were soaked for up to 12 days in a cell-culture solution. Pure magnesium lost mass at an average of 31.41 mg/cm2/day and was completely corroded by day 12. The 20% and 40% composites lost 1.26 and 2.65 mg/cm2/day. Adding 20% bredigite raised hardness by 68% and ultimate compressive strength by 67%. That composite's ultimate compressive strength fell from 190 MPa to about 130 MPa over 12 days. Rat bone marrow stromal cells attached better to the 20% composite. Extracts of the 40% composite stimulated cell growth, and raised a bone-cell marker enzyme more than magnesium extracts did. Undiluted magnesium extracts inhibited cell growth. The authors concluded that bredigite slowed degradation by up to 24 times. They noted that edge defects and impurities in the magnesium may have contributed to pitting corrosion.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory materials study: composites made from powders, then tested for structure, mechanical strength, degradation in solution and electrochemistry, plus in vitro cell-culture tests
• Who was studied: Laboratory-made specimens of pure magnesium and magnesium-bredigite composites, and rat bone marrow stromal cells (rBMSCs) grown in culture. The article does not state the number of specimens.
• Exposure: No asbestos exposure was studied. The materials were magnesium powder mixed with bredigite (Ca7MgSi4O16) powder at 20 and 40 vol.%, immersed in HEPES-buffered DMEM for up to 12 days. Cell tests used the 20% composite (attachment) and extracts of the 40% composite (cytotoxicity and ALP).
• Main results:
  • Average degradation rate after 12 days: 31.41 mg/cm2/day for pure magnesium, compared with 1.26 mg/cm2/day for the Mg-20% bredigite composite and 2.65 mg/cm2/day for the Mg-40% bredigite composite
  • Pure magnesium was completely corroded by day 12, and the solution reached pH 9.8
  • Adding 20 vol.% bredigite increased the microhardness of magnesium by 68% and its ultimate compressive strength by 67%
  • During immersion, the ultimate compressive strength of the composites fell from 190 MPa to about 130 MPa over 12 days
  • Rat bone marrow stromal cells showed better early attachment to the Mg-20% bredigite composite than to pure magnesium
  • Undiluted extracts of pure magnesium significantly inhibited cell proliferation, while diluted extracts led to enhanced proliferation
  • Extracts of the Mg-40% bredigite composite stimulated rBMSC proliferation more than magnesium extracts did
  • Extracts of the Mg-40% bredigite composite produced significantly higher ALP (alkaline phosphatase) activity than magnesium extracts (p less than 0.05). The difference between the 1/4 and 1/16 dilutions of the composite extract was not statistically significant.
• The authors' conclusion: The authors concluded that adding bredigite could slow the biodegradation of magnesium by up to 24 times. They also concluded that the composites could have potential for orthopedic use, prompting further in vitro and in vivo study.
• Limitations the authors state:
  • Pores and cracks at the edges of the specimens, formed during processing, made the structure uneven from core to surface, and this negatively affected degradation behavior
  • Iron and nickel impurities in the magnesium powder were above their tolerance limits and may have contributed to pitting corrosion
  • The HEPES buffer added to the test solution affected the results; the authors state that degradation would have been lower without it
  • Large scatter in the mechanical data for the 40% composite suggested its structure was relatively uneven
  • The hydrogen gas released at the measured mass losses is still above the level the body can tolerate
  • The mechanism behind the improved cell attachment is unclear, and the authors could not determine which ions caused the raised ALP activity

Topics

The National Library of Medicine indexes this study under subjects our site covers: Tremolite.

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