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Magnesium and its alloys have in recent years emerged as a promising alternative to titanium-based implants for medical applications due to favorable degradation properties and good biocompatibility. The degradation of materials is currently investigated by studying different samples of the same material at different time points after degradation in a medium. This study is presenting a high-resolution time-lapse investigation of Mg-2Ag in culture medium using synchrotron radiation-based micro-computed tomography over the course of 5 days. The design of the custom-built corrosion cell and bioreactor are described. The computed degradation rate after 5 days is in agreement with the literature. SRµCT enables the segmentation of cracks forming in the degradation layer due to stresses and hydrogen development.

The present work applies the law of mass conservation toward an analytical model describing the long-term degradation of Mg-0.3Ca implant material in defined physiological electrolyte environments. The model takes into account surface conversion and degradation product deposition related changes of degradation rates by introducing an effective layer thickness. The analytical nature of the approach does not consider detailed chemical and electrochemical process. Thus, it simply declares an effective damping term. In this way it can be applied easily for the prediction of materials failure in the named environments. Restrictions of the approach will be discussed as well since validity relates to a number of aspects.

Magnesium-based implants exhibit several advantages, such as biodegradability and possible osteoinductive properties. Whether the degradation may induce cell type-specific changes in metabolism still remains unclear. To examine the osteoinductivity mechanisms, the reaction of bone-derived cells (MG63, U2OS, SaoS2, and primary human osteoblasts (OB)) to magnesium (Mg) was determined. Mg-based extracts were used to mimic more realistic Mg degradation conditions. Moreover, the influence of cells having direct contact with the degrading Mg metal was investigated. In exposure to extracts and in direct contact, the cells decreased pH and osmolality due to metabolic activity. Proliferating cells showed no significant reaction to extracts, whereas differentiating cells were negatively influenced. In contrast to extract exposure, where cell size increased, in direct contact to magnesium, cell size was stable or even decreased. The amount of focal adhesions decreased over time on all materials. Genes involved in bone formation were significantly upregulated, especially for primary human osteoblasts. Some osteoinductive indicators were observed for OB: (i) an increased cell count after extract addition indicated a higher proliferation potential; (ii) increased cell sizes after extract supplementation in combination with augmented adhesion behavior of these cells suggest an early switch to differentiation; and (iii) bone-inducing gene expression patterns were determined for all analyzed conditions. The results from the cell lines were inhomogeneous and showed no specific stimulus of Mg. The comparison of the different cell types showed that primary cells of the investigated tissue should be used as an in vitro model if Mg is analyzed. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 165-179, 2017.

Binary magnesium–silver (Mg–Ag) alloys were designed as antibacterial material to treat infections in an implant site. The mechanical and electrochemical measurements were performed on three casting Mg–Ag alloys under cell culture conditions. The composition and distribution of the corrosion layer was analyzed by microscopy and X-ray photoelectron spectroscopy. In cell culture media, Mg–Ag alloys show higher, but still acceptable general corrosion rates while less susceptibility to pitting corrosion than pure Mg with increasing content of silver. This study indicates that Mg–Ag alloys have satisfactory corrosion properties and much better mechanical properties than pure magnesium as a functional biodegradable material.

Permanent implants have to fulfill a great variety of requirements related to both material and geometry. In addition, manufacturing costs play a role, which is getting steadily more and more important. Metal Injection Molding (MIM) of titanium alloy powders may contribute to the development of implants with higher functionality without increasing the price. High degree of freedom with regard to geometry, high material efficiency, and the possibility to create even porous structures are main benefits from applying this technique. Today, even long-term implants made from Ti–6Al–4V by MIM are commercially available. However, in order to improve fatigue behavior it is beneficial to perform a minor variation of Ti–6Al–4V by adding a low amount of boron. In this paper the mechanical, biological, and corrosion properties of specimens manufactured from Ti–6Al–4V–0.5B alloy by MIM are presented. In order to exclude unknown reactions in the body environment due to the boron content, corrosion, and biological tests are performed. Tensile and fatigue tests characterize the mechanical properties. Potentiodynamic polarization and electrochemical impedance spectroscopy are done in comparison to wrought and to MIM processed Ti–6Al–4V material. For cell experiments cancellous bone cells are cultured to perform adhesion, proliferation, and viability experiments. The results presented here show that the alloy Ti–6Al–4V–0.5B satisfies all basic needs of a material for highly loaded permanent implants manufactured by MIM.

In living organisms the natural contact areas between cells are the cell membranes. These membranes separate the individual cells or build reaction compartments in an aqueous environment. Beside their structural role they also have specific functions that are due to the great variety of their components which are lipids (about 40%) and proteins (about 60%). In terms of implant development the next neighbors of the cells are artificial materials which do not belong to the natural cellular environment. Therefore, a biocompatible implant surface is needed which is achieved by either the correct choice of the material and surface roughness or a functionalization of the surface. To date little is known of the role lipids could play in this context. However, from literature we know that phospholipids can cause calcification and that modified phosphorylcholine polymers ('MPC polymers') are used to decrease cell adhesion and to improve blood compatibility. In the last few years it became obvious that the lipid contribution in the membrane is not only important as support for proteins but that the lipid membrane itself can also be a target for drug design and its structure can influence the function of the proteins. We therefore focused our interest on this class of amphiphilic molecules. In this work we present initial observations on the modification of metallic implant surfaces of Ti-6Al-7Nb (in mass percent) by phospholipid multilayers, using contact angle measurements and surface sensitive characterization techniques such as scanning electron microscopy (SEM) and scanning force microscopy (SFM). Preliminary data concerning cell adhesion experiments are also presented.