Enhanced in-vitro biodegradation, bioactivity, and mechanical properties of Mg-based biocomposite via addition of calcium-silicate-based bioceramic through friction stir processing as resorbable temporary bone implant
Maryam Mehdizade, A.R. Eivani, Fatemeh Tabatabaei, Seyed Hashem Mousavi Anijdan, H.R. Jafarian
Abstract
Bioabsorbable Mg and alloys have been used as orthopedic implant biomaterials due to their similar mechanical properties to human natural bone. Low bioactivity and high biodegradation rate are the main reasons for limiting clinical applications of Mg and alloys in biological media. In order to achieve long-lasting bio applications of bioabsorbable WE43 Mg alloy, it is necessary to improve strength and bioactivity and control biodegradation rate of this material. In this study, Mg-based composites are produced using friction stir processing (FSP) by addition of wollastonite (CaSiO3) calcium-silicates-based bioactive reinforcing agent into Mg matrix. The results showed that applied severe plastic deformation during FSP caused formation of ultra-fine grain structure with homogenous distribution of secondary phase particles, which resulted in a remarkable improvement of ductility and strength of FSPed Mg matrix. Also, biodegradation behavior of resulting composite was evaluated using electrochemical and in-vitro immersion tests in simulated body fluid (SBF) and phosphate-buffered saline (PBS). The results revealed that processed bioabsorbable Mg alloy showed a lower biodegradation rate compared to monolithic Mg alloy. Furthermore, the presence of wollastonite bioceramic particles significantly enhanced strength and reduced biodegradation of the Mg-based composite. Moreover, the addition of wollastonite bioceramic particles positively affected the bioactivity of Mg matrix by forming a cauliflower shaped bone-like hydroxyapatite layer on the surface after 28 days of immersion in SBF.