In Vivo Study on Degradation Behavior and Histologic Response of Pure Magnesium in Muscles

doi:10.1016/j.jmst.2016.09.011

Abstract

Abstract:

When an orthopedics device is implanted into bone injury site, it will contact the soft tissue (skeletal muscle, fascia, ligament etc.) except for bone. Magnesium based biodegradable metals are becoming an important research object in orthopedics due to their bioactivity to promote bone healing. In this study, pure Mg rods with and without chemical conversion coating were implanted into the muscle tissue of rabbits. Implants and their surrounding tissues were taken out for weight loss measurement, cross-sectional scanning electron microscopy observation, elemental distribution analysis and histological examination. The results showed that the chemical conversion coating would increase the in vivo corrosion resistance of pure Mg and decrease the accumulation of calcium (Ca) and phosphorus (P) elements around the implants. For the bare magnesium implant, both Ca and P contents in the surrounding tissues increased at the initial stage of implantation and then decreased at 12 weeks implantation, while for the magnesium with chemical conversion coating, Ca and P contents in the surrounding tissues decreased with the implantation time, but were not significant. The histological results demonstrated that there was no calcification in the muscle tissue with implantation of magnesium for up to 12 weeks. The chemical conversion coating not only increased the in vivo corrosion resistance of pure Mg, but also avoided the depositions of Ca and P in the surrounding tissues, meaning that pure magnesium should be bio-safe when contacting with muscle tissues.

Key words: Pure magnesium, Degradation behavior, Histologic response, Muscle tissue

Chen Shanshan, Tan Lili, Zhang Bingchun, Xia Yonghui, Xu Ke, Yang Ke. In Vivo Study on Degradation Behavior and Histologic Response of Pure Magnesium in Muscles[J]. J. Mater. Sci. Technol., 2017, 33(5): 469-474.

Figures/Tables 9

Fig. 1. Surface morphology (a) and cross-section morphology (b) of chemical conversion coating.

Table 1. The chemical composition of chemical conversation coating

Element	wt%	at.%
O K	7.03	9.10
F K	49.10	53.54
Mg K	43.87	37.37
Total	100.00

Fig. 2. Weight loss of magnesium with and without fluoride conversion coating during implantation in rabbit muscle tissues.

Fig. 3. Sectional morphologies of magnesium samples with and without chemical conversion coating surrounding with muscle tissues during different implantation periods in rabbits: (a) Mg—1 week, (b) Mg—2 weeks, (c) Mg—4 weeks, (d) Mg—12 weeks, (e) coating treated Mg—1 week, (f) coating treated Mg—2 weeks, (g) coating treated Mg—4 weeks, (h) coating treated Mg—12 weeks.

Fig. 4. Morphology and EDS of one point on each sample: (a) cross-section morphology of sample, and the position of the selected point, (b) EDS result about the elements contained in the selected point area.

Fig. 5. Ca (a) and P (b) distributions tendency in muscle tissues around the pure Mg implants without coating implanted for different time.

Fig. 6. Ca (a) and P (b) distributions tendency in muscle tissues around the pure Mg implants with chemical conversion coating implanted for different time.

Fig. 7. Released profile of F ion in vitro.

Fig. 8. Histological photos of muscle tissue implanted with bare pure Mg (a1, a2) and pure magnesium with chemical conversion coating (b1, b2) for 12 weeks after a hematoxylin-eosin staining.

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