The effects of surface treatments on electron beam melted Ti-6Al-4V disks on osteogenesis of human mesenchymal stromal cells

Chemical etching of Ti-6Al-4V biomaterials fabricated by selective laser melting enhances mesenchymal stromal cell mineralization

Porous titanium scaffolds fabricated by powder bed fusion additive manufacturing techniques have been widely adopted for orthopedic and bone tissue engineering applications. Despite the many advantages of this approach, topological defects inherited from the fabrication process are well understood to negatively affect mechanical properties and pose a high risk if dislodged after implantation. Consequently, there is a need for further post-process surface cleaning. Traditional techniques such as grinding or polishing are not suited to lattice structures, due to lack of a line of sight to internal features. Chemical etching is a promising alternative; however, it remains unclear if changes to surface properties associated with such protocols will influence how cells respond to the material surface. In this study, we explored the response of bone marrow derived mesenchymal stem/stromal cells (MSCs) to Ti-6Al-4V whose surface was exposed to different durations of chemical etching. Cell morphology was influenced by local topological features inherited from the SLM fabrication process. On the as-built surface, topological nonhomogeneities such as partially adhered powder drove a stretched anisotropic cellular morphology, with large areas of the cell suspended across the nonhomogeneous powder interface. As the etching process was continued, surface defects were gradually removed, and cell morphology appeared more isotropic and was suggestive of MSC differentiation along an osteoblastic-lineage. This was accompanied by more extensive mineralization, indicative of progression along an osteogenic pathway. These findings point to the benefit of post-process chemical etching of additively manufactured Ti-6Al-4V biomaterials targeting orthopedic applications.

Ultrathin TiO2 Coatings via Atomic Layer Deposition Strongly Improve Cellular Interactions on Planar and Nanotubular Biomedical Ti Substrates

This work aims to investigate the chemical and/or structural modification of Ti and Ti-6Al-4V (TiAlV) alloy surfaces to possess even more favorable properties toward cell growth. These modifications were achieved by (i) growing TiO2 nanotube layers on these substrates by anodization, (ii) surface coating by ultrathin TiO2 atomic layer deposition (ALD), or (iii) by the combination of both. In particular, an ultrathin TiO2 coating, achieved by 1 cycle of TiO2 ALD, was intended to shade the impurities of F- and V-based species in tested materials while preserving the original structure and morphology. The cell growth on TiO2-coated and uncoated TiO2 nanotube layers, Ti foils, and TiAlV alloy foils were compared after incubation for up to 72 h. For evaluation of the biocompatibility of tested materials, cell lines of different tissue origin, including predominantly MG-63 osteoblastic cells, were used. For all tested nanomaterials, adding an ultrathin TiO2 coating improved the growth of MG-63 cells and other cell lines compared with the non-TiO2-coated counterparts. Here, the presented approach of ultrathin TiO2 coating could be used potentially for improving implants, especially in terms of shading problematic F- and V-based species in TiO2 nanotube layers.

Advances and Prospects in Materials for Craniofacial Bone Reconstruction

The craniofacial region is composed of 23 bones, which provide crucial function in keeping the normal position of brain and eyeballs, aesthetics of the craniofacial complex, facial movements, and visual function. Given the complex geometry and architecture, craniofacial bone defects not only affect the normal craniofacial structure but also may result in severe craniofacial dysfunction. Therefore, the exploration of rapid, precise, and effective reconstruction of craniofacial bone defects is urgent. Recently, developments in advanced bone tissue engineering bring new hope for the ideal reconstruction of the craniofacial bone defects. This report, presenting a first-time comprehensive review of recent advances of biomaterials in craniofacial bone tissue engineering, overviews the modification of traditional biomaterials and development of advanced biomaterials applying to craniofacial reconstruction. Challenges and perspectives of biomaterial development in craniofacial fields are discussed in the end.

Surface Modification of Biomedical Ti-18Zr-15Nb Alloy by Atomic Layer Deposition and Ag Nanoparticles Decoration

Superelastic biocompatible alloys attract significant attention as novel materials for bone tissue replacement. These alloys are often composed of three or more components that lead to the formation of complex oxide films on their surfaces. For practical use, it is desirable to have a single-component oxide film with a controlled thickness on the surface of biocompatible material. Herein we investigate the applicability of the atomic layer deposition (ALD) technique for surface modification of Ti-18Zr-15Nb alloy with TiO₂ oxide. It was found that a 10-15 nm thick, low-crystalline TiO₂ oxide layer is formed by ALD method over the natural oxide film (~5 nm) of the Ti-18Zr-15Nb alloy. This surface consists of TiO₂ exclusively without any additions of Zr or Nb oxides/suboxides. Further, the obtained coating is modified by Ag nanoparticles (NPs) with a surface concentration up to 1.6% in order to increase the material's antibacterial activity. The resulting surface exhibits enhanced antibacterial activity with an inhibition rate of more than 75% against E. coli bacteria.