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Selected Publication:
Myrissa, A.
Biocompatibility analysis of different resorbable Magnesium alloys in a rat model
Doktoratsstudium der Medizinischen Wissenschaft; Humanmedizin; [ Dissertation ] Graz Medical University; 2016. pp.
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- Authors Med Uni Graz:
- Advisor:
- Schäfer Ute
- Weinberg Annelie-Martina
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- Abstract:
- Introduction Biodegradable Magnesium (Mg) materials are under investigation because of their promising properties as orthopaedic devices. Different chemical elements like Rare Earth Elements (REE) are used as alloying elements in the Mg alloys to enhance the mechanical properties and the degradation resistance. Their possible usage in bone fractures, especially in children, raises many questions regarding their applicability and safety. In most of the studies, the degradation properties and the biocompatibility of Mg alloys are analyzed in vivo by using micro-focused Computer Tomography (µCT). However, histological analysis with Technovit 9100 New embedding method can provide further and more detailed information about how and whether the degradation performance can affect and interfere with the bone cells during the bone healing process. Materials and Methods Distal epiphysis femoral bones were used to establish histological staining protocols for rat bones embedded in Technovit 9100 New. Cylindrical pins of pure Mg (99.99%) and two binary Mg alloys, Mg2Ag and Mg10Gd, were used to investigate the degradation behaviour in growing Sprague-Dawley® rats in a long-term study of 36 weeks. In vivo medium resolution µCT scans were performed at 1, 4, 12, 24 and 36 weeks post-operative to observe the longitudinal degradation of each alloy within the same animal. Moreover, ex vivo high resolution µCT scans and the corresponding bone sections stained with Toluidine Blue-O were conducted at 1 and 24 weeks after the operation. Additionally, Mg and Gadolinium (Gd) elemental distribution within the organs was studied at 4, 12, 24 and 36 weeks. Results All the performed stainings worked properly at Technovit 9100 New embedded samples. Moreover, a slower degradation of pure Mg and Mg2Ag in comparison to the fast disintegrating Mg10Gd was displayed. Pure Mg and Mg2Ag were well integrated and surrounded by bone tissue 24 weeks after implantation. Both of these alloys showed no adverse reactions to the bone during their moderate degradation. On the contrary, Mg10Gd remnants, appearing 12 weeks post-operative, disturbed the bone remodeling until the end of the study because of its fast disintegration. The distribution of Mg and Gd elements showed that Gd was accumulated especially in spleen, lung, liver and kidney rat organs even 36 weeks post-operative, whereas, no accumulation of Mg and Gd ions was observed in blood serum samples. Discussion Histological analysis of the bone tissue embedded in Technovit 9100 New can provide detailed information about the real in vivo conditions on a cellular level. Mg10Gd induces less beneficial tissue reactions, while Mg2Ag showed moderate and adequate biodegradation and no adverse reactions in bone healing process which might be promising as an orthopaedic device. It is also shown that more extended studies regarding the biodegradation of the Mg alloys in parallel with the distribution of the alloying elements in organs and blood serum are necessary.