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Name (Title):
Akiko Yamamoto (Group Leader)
Affiliation:
Metallic Biomaterials Group, Biomaterials Center, NIMS
Address:
1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
Email: yamamoto.akiko@nims.go.jp
Home Page: http://www.nims.go.jp/bmc/group/metallic/
Presentation Title:
Biocompatibility evaluation of bioabsorbable magnesium alloys
Abstract:
Magnesium (Mg) and its alloys were first applied to orthopaedic implants in early 20’s
century, but recent attempts on stent application open a new stage as a bioabsorbable metal.
However, available biocompatibility data of Mg and its alloys is restricted. Since Mg generates
H2 and OH - along the progress of its corrosion reaction with water, the pH of the fluid around Mg
surface will increase, which may affect surrounding cellular and tissue function. In this study,
biocompatibility of Mg and its alloys is examined by cell culture method in vitro.
The materials used are pure Mg, AZ31, AZ61, and AZ80. The disks of 9.5 mm in diameter or
the plates of 8 x 9 mm and 2 mm in thickness were prepared. Every surface of these specimens
was polished with #600(14µm) SiC paper and washed with acetone. Murine fibroblast L929
were seeded at the concentration of 1000 cells/mL in Eagle’s minimum essential medium
supplemented with 10 % (v/v) of fetal bovine serum and cultured in a 5%(v/v) CO2 incubator for
1, 4, and 7 d. Then, the number of viable cells was estimated by WST-1 assay. Mg 2+ in the
culture medium was quantified by a colorimetric method.
The highest cell growth was observed for AZ31, followed by pure Mg. Cell growth was very
low for AZ61 and AZ80. The highest release of Mg 2+ was observed for pure Mg, followed by
AZ31, AZ61, and AZ80 in the order. This indicates that corrosion reaction is more active at the
surface of pure Mg rather than those of AZ61 and AZ80. Therefore, the lower cell growth at the
surface of AZ61 and AZ80 is not simply attributed to the increase of pH of the fluid near the
specimen surface due to corrosion reaction. In the case of aluminum (Al)-containing Mg alloys,
Al condensation in the surface oxide layer was observed after immersion into NaCl solution [1] . It
is also reported that PVD film of pure Al has lower cell attachment and survival ratio than those
of glass [2] . These facts suggest that higher content of Al may reduce the cell attachment and
growth on Al-containing Mg alloys.
References:
[1] H. Kita, et al. J. Jpn. Inst. of Metals, 69:805-809(2005).
[2] A. Yamamoto et al. J. Jpn. Soc. for Biomater., 18:87-94(2000).
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Oral Presentation 10