In Vitro Cytotoxicity of Possible Corrosion Products from Mg-Based Biodegradable Metals: Magnesium Oxide and Magnesium Hydroxide Nanoparticles

Preparation of a novel antibacterial magnesium carbonate coating on a titanium surface and its in vitro biocompatibility

Magnesium-based coatings have attracted great attention in surface modification of titanium implants due to their superior angiogenic and osteogenic properties. However, their biological effects as a carbonate-based constituent remain unrevealed. In this study, magnesium carbonate coatings were prepared on titanium surfaces under hydrothermal conditions and subsequently treated with hydrogen peroxide. Also, their antibacterial activity and in vitro cell biocompatibility were evaluated. The obtained coatings consisted of nanoparticles without cracks and exhibited excellent adhesion to the substrate. X-ray diffraction (XRD) results indicated pure magnesium carbonate coatings formed on the Ti surface after hydrothermal treatment. After hydrogen peroxide treatment, the phase composition of the coatings had no obvious change. Compared to the untreated coatings, the hydrogen peroxide-treated coatings showed increased surface roughness and hydrophilicity. Co-culture with Staphylococcus aureus (S. aureus) demonstrated that the obtained coatings had good antibacterial activity. In vitro cell culture results showed that the hydrogen peroxide-treated coatings enhanced the viability, proliferation, and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). These findings suggest that this MgCO3-based coating exhibits excellent antibacterial performance and osteogenic potential. Based on the above, this study provides a simple method for preparing titanium implants with dual antibacterial and osteogenic capabilities, holding great promise in clinical applications.

Nanosized Silk-Magnesium Complexes for Promotion of Angiogenic and Osteogenic Activities

Injectable hydrogels with osteogenic and angiogenetic properties are of interest in bone tissue engineering. Since the bioactivity of ions is concentration-dependent, nanosized silk-magnesium (Mg) complexes were previously developed and assembled into hydrogels with angiogenic capabilities but failed to control both osteogenic and angiogenetic activities effectively. Here, nanosized silk particles with different sizes were obtained by using ultrasonic treatment to control silk-Mg coordination and particle formation, resulting in silk-Mg hydrogels with different types of bioactivity. Fourier transform infrared and X-ray diffraction results revealed that different coordination intensities were present in the different complexes as a basis for the differences in activities. Slow Mg ion release was controlled by these nanosized silk-Mg complexes through degradation. With the same amount of Mg ions, the different silk-Mg complexes exhibited different angiogenic and osteogenic capacities. Complexes with both angiogenic and osteogenic capacities were developed by optimizing the sizes of the silk particles, resulting in faster and improved quality of bone formed in vivo than complexes with the same composition of silk and Mg but only angiogenic or osteogenic capacities. The biological selectivity of silk-Mg complexes should facilitate applications in tissue regeneration.

Characterization of hFOB 1.19 Cell Line for Studying Zn-Based Degradable Metallic Biomaterials

In vitro testing is the first important step in the development of new biomaterials. The human fetal osteoblast cell line hFOB 1.19 is a very promising cell model; however, there are vast discrepancies in cultivation protocols, especially in the cultivation temperature and the presence of the selection reagent, geneticin (G418). We intended to use hFOB 1.19 for the testing of Zn-based degradable metallic materials. However, the sensitivity of hFOB 1.19 to zinc ions has not yet been studied. Therefore, we compared the toxicity of zinc towards hFOB 1.19 under different conditions and compared it with that of the L929 mouse fibroblast cell line. We also tested the cytotoxicity of three types of Zn-based biomaterials in two types of media. The presence of G418 used as a selection reagent decreased the sensitivity of hFOB 1.19 to Zn2+. hFOB 1.19 cell line was more sensitive to Zn2+ at elevated (restrictive) temperatures. hFOB 1.19 cell line was less sensitive to Zn2+ than L929 cell line (both as ZnCl2 and extracts of alloys). Therefore, the appropriate cultivation conditions of hFOB 1.19 during biomaterial testing should be chosen with caution.

Zn doped CaP coatings used for controlling the degradation rate of MgCa1 alloy: In vitro anticorrosive properties, sterilization and bacteria/cell-material interactions

The purpose of this study was to investigate the effect of Zn doped CaP coatings prepared by micro-arc oxidation method, as a possible approach to control MgCa1 alloy degradation. All the prepared coatings comprised a calcium deficient CaP phase. The control in this evaluation was performed with undoped CaP coating in SBF solution at body temperature (37 ± 0.5⁰C). The investigation involved determination of microchemical, mechanical, morphological, properties along with anticorrosive, cytocompatibility and antibacterial efficacy. The effect of sterilization process on the properties of the surfaces was also investigated. The results showed that the addition of Zn into CaP increased the corrosion resistance of MgCa1 alloy. Moreover, the adhesion strength of the coatings to MgCa1 alloy was enhanced by Zn addition. In cytotoxicity testing of the samples, extracts of the samples in MEM were incubated with L929 cells and malformation, degeneration and lysis of the cells were examined microscopically after 72 h. The results showed that all samples were cytocompatible. The degradation of MgCa1 alloy in the simulated body fluids (SBF) or DMEM was decreased by coating with CaP. Moreover, the degradation rate of CaP was further decreased by adding a small amount of Zn into the CaP matrix. The samples having CaP coatings and Zn doped CaP coating demonstrated antibacterial efficacy against E.coli. As a result, coating of magnesium alloy with Zn-doped CaP decreased the degradation rate, increased the corrosion resistance, cytocompatibility and the antibacterial effects of the alloys.

Structural and physicochemical properties of Rheum emodi mediated Mg(OH)2 nanoparticles and their antibacterial and cytotoxic potential

In the present investigation, Rheum emodi roots extract mediated magnesium hydroxide nanoparticles [Mg(OH)2 NPs] through the bio-inspired experimental technique were synthesised. Mg(OH)2 NPs were characterised by using various characterisation techniques such as field emission scanning electron microscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and ultraviolet-visible spectroscopy. The formation of Mg(OH)2 NPs was confirmed by X-ray diffraction. The structural analysis confirmed the hexagonal crystal symmetry of Mg(OH)2 NPs with space group P-3m1 and space group no. 164 using the Rietveld refinement technique. TEM micrographs illustrated the nano-size formation of Mg(OH)2 NPs of spherical shape and size ∼14.86 nm. With the aid of FTIR data, plant metabolites such as anthraquinones have been identified as a stabilising and reducing agent for the synthesis of biogenic Mg(OH)2 NPs. The synthesised Mg(OH)2 NPs showed antimicrobial and cytotoxic potential against Gram-negative and Gram-positive bacteria such as Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923) and MDA-MB-231 human breast cancer cell lines.

Assessment of Cytotoxicity of Magnesium Oxide and Magnesium Hydroxide Nanoparticles using the Electric Cell-Substrate Impedance Sensing

Magnesium (Mg)-based alloys have the potential for bone repair due to their properties of biodegradation, biocompatibility, and structural stability, which can eliminate the requirement for a second surgery for the removal of the implant. Nevertheless, uncontrolled degradation rate and possible cytotoxicity of the corrosion products at the implant sites are known current challenges for clinical applications. In this study, we assessed in vitro cytotoxicity of different concentrations (0 to 50 mM) of possible corrosion products in the form of magnesium oxide (MgO) and magnesium hydroxide (Mg(OH)2) nanoparticles (NPs) in human fetal osteoblast (hFOB) 1.19 cells. We measured cell proliferation, adhesion, migration, and cytotoxicity using a real-time, label-free, non-invasive electric cell-substrate impedance sensing (ECIS) system. Our results suggest that 1 mM concentrations of MgO/Mg(OH)2 NPs are tolerable in hFOB 1.19 cells. Based on our findings, we propose the development of innovative biodegradable Mg-based alloys for further in vivo animal testing and clinical trials in orthopedics.