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High-pressure torsion (HPT) can refine the microstructure and consequently modify the properties, such as mechanical and corrosion properties, of Mg and its alloys. Biodegradable magnesium materials alloyed with the essential elements of life, such as Ca and Sr, are a current research frontier. In this study, biodegradable ultrafine-grained pure Mg, Mg–Ca alloy, and Mg–Sr alloy were prepared using HPT processing. The microstructure, mechanical properties, biodegradable behaviors, and biocompatibility in vitroand in vivoof these materials were systematically investigated. Our results revealed that HPT pure Mg with a bimodal and ultrafine-grained microstructure showed higher mechanical strength, ductility, and degradation rate compared with the as-received materials. The good biocompatibility of HPT pure Mg was confirmed both in vitroand in vivo. The HPT Mg–Ca alloy and Mg–Sr alloy with homogeneous ultrafine-grained microstructures showed higher mechanical strength and lower degradation rate than their as-cast counterparts. The good biocompatibility of the HPT Mg–Ca alloy and Mg–Sr alloy was also revealed. All these findings indicate that HPT is an alternative avenue to fabricate biodegradable Mg-based materials.

Correction for ‘Construction of perfluorohexane/IR780@liposome coating on Ti for rapid bacteria killing under permeable near infrared light’ by Xiuhua Wang et al., Biomater. Sci., 2018, 6, 2460–2471, https://doi.org/10.1039/C8BM00602D.

Xenograft, namely bone-derived biological apatite (BAp), is widely recognized as a favorable biomaterial in bone tissue engineering owing to its biodegradability, biocompatibility, and osteoconductive properties. Substitutions of endogenous trace ions are thought to improve the osteogenic capacity of xenograft compared with synthetic hydroxyapatite (HAp). In order to modify the physicochemical and biological properties of apatite, different approaches to induce trace ion incorporation have been widely considered. In this study, we demonstrated that the incorporation of fluoride ions into porcine bone-derived biological apatite (pBAp) contributes to altered crystal morphology of the apatite, the sustained release of fluoride, and the in siturelease of endogenous trace ions (e.g., magnesium and calcium) into the peripheral tissue microenvironment. This ionic balanced perimaterial microenvironment not only led to superior proliferation and osteogenic differentiation of rat bone mesenchymal stem cells (rBMSCs), but also accelerated new bone formation of the calvarial defect on a rat model viathe activation of Wnt/β-catenin signaling. These promising observations may be attributed to the controlled release of endogenous trace ions from the xenograft to the peripheral tissue microenvironment driven by fluoride ion incorporation. Lastly, this study may provide a new insight to strengthen the osteogenicity of xenografts for clinical applications in the future.