A study of Titanium and Magnesium particle-induced oxidative stress and toxicity to human osteoblasts.

Hybrid implants combine both Titanium (Ti) and Magnesium (Mg) are prevalent nowadays. The long-term implications of Ti and Mg implants within the human body are not yet fully understood. Many implant failure cases due to inflammation, allergic responses, and aspect loosening have been reported frequently. Particles generated through daily wear and tear of implants may worsen the situation by causing acute complications. An in-depth understanding of the behavior of metal particles with human osteoblasts is necessary. In this study, a novel and systematic attempt was made to understand the effects of different concentrations of Ti and Mg particles to the osteoblastic SAOS2 cell: toxicity, alterations to mitochondria, and changes to the specific gene and protein expression. Ti particles were found toxic to SAOS2 cells at different dosages, while Mg particles at lower concentrations could improve cell viability. To understand this phenomenon better, we have measured cellular reactive oxygen species (ROS) production and cell apoptosis & necrosis percentage. We also have checked the mitochondrial structure with transmission electron microscope (TEM), and mitochondrial function using Tetramethyl rhodamine, ethyl ester staining (TMRE). NDUFB6, SDHC, and ATP5F1 were the essential mitochondrial genes involved in the ROS production and ATP production. Immunocytochemistry (ICC) and real-time polymerase chain reaction (qPCR) were implemented to check the regulations of these related genes.

Fabrication of Ti + Mg composites by three-dimensional printing of porous Ti and subsequent pressureless infiltration of biodegradable Mg.

A semi-degradable Ti + Mg composite with superior compression and cytotoxicity properties have been successfully fabricated using ink jet 3D printing followed by capillary mediated pressureless infiltration technique targeting orthopaedic implant applications. The composite exhibited low modulus (~5.2 GPa) and high ultimate compressive strength (~418 MPa) properties matching that of the human cortical bone. Ti + Mg composites with stronger 3D interconnected open-porous Ti networks are possible to be fabricated via 3D printing. Corrosion rate of samples measured through immersion testing using 0.9%NaCl solution at 37 °C indicate almost negligible corrosion rate for porous Ti (~1.14 µm/year) and <1 mm/year for Ti + Mg composites for 5 days of immersion, respectively. The composite significantly increased the SAOS-2 osteoblastic bone cell proliferation rate when compared to the 3D printed porous Ti samples and the increase is attributed to the exogenous Mg2+ ions originating from the Ti + Mg samples. The cell viability results indicated absent to mild cytotoxicity. An attempt is made to discuss the key considerations for net-shape fabrication of Ti + Mg implants using ink jet 3D printing followed by infiltration approach.