Osteoblast Responses to Titanium-Coated Subcellular Scaled Microgrooves

Mechanical and morphological responses of osteoblast-like cells to two-photon polymerized microgrooved surfaces

Microgrooved surfaces are recognized as an important strategy of tissue engineering to promote the alignment of bone cells. In this work, we have investigated the mechanical and morphological aspects of osteoblasts cells after interaction with different micro-structured polymeric surfaces. Femtosecond laser writing technique was used for the construction of circular and parallel microgrooved patterns in biocompatible polymeric surfaces based on pentaerythritol triacrylate. Additionally, we have studied the influence of the biocompatible TiO₂ nanocrystals (NCs) related to the cell behavior, when incorporated to the photoresin. The atomic force microscopy technique was used to investigate the biomechanical reaction of the human osteoblast-like MG-63 cells for the different microgroove. It was demonstrated that osteoblasts grown on circular microgrooved surfaces exhibited significantly larger Young's modulus compared to cells sown on flat films. Furthermore, we could observe that TiO₂ NCs improved the circular microgrooves effects, resulting in more populated sites, 34% more elongated cells, and increasing the cell stiffness by almost 160%. These results can guide the design and construction of effective scaffold surfaces with circular microgrooves for tissue engineering and bone regeneration.

Graphene Oxide-Modified Concentric Microgrooved Titanium Surfaces for the Dual Effects of Osteogenesis and Antiosteoclastogenesis

Surface modification is an effective method to resolve the biocompatibility, mechanical, and functional issues of various titanium implant materials. Therefore, many researchers have modified the implant surface to promote the osseointegration of the implant and improve the implant survival rate. In this study, we used photolithography to construct concentric microgrooves with widths of 10 μm and depths of 10 μm, to produce an osteon-mimetic concentric microgrooved titanium surface that was further modified with graphene oxide by silanization (GO-CMS). The modified surface had great biocompatibility and promoted the proliferation of bone marrow-derived mesenchymal stem cells (BMSCs) and RAW264.7 macrophages. The concentric microgrooves on the titanium surface guided cell migration, altered actin cytoskeleton, and caused the cells to arrange in concentric circles. The titanium surface of the GO-modified osteon-mimetic concentric microgrooves promoted the osteogenic differentiation of BMSCs and inhibited the osteoclastogenic differentiation of RAW264.7 cells. Subsequently, we constructed an indirect coculture system and found that RAW264.7 cells cultured on a GO-CMS material surface in a BMSC-conditioned medium (BCM) decreased receptor activator of nuclear factor-κB ligand (RANKL) secretion and increased OPG secretion and also that the BCM inhibited osteoclastogenic differentiation. Additionally, the secretion of OSM increased in BMSCs cultured in RAW264.7-conditioned medium (RCM) in the GO-CMS group, which in turn promoted the osteogenic differentiation of BMSCs. In conclusion, the titanium surface of GO-modified osteon-mimetic concentric microgrooves had dual effects of osteogenesis and antiosteoclastogenesis under single and coculture conditions, which is beneficial for implant osseointegration and is a promising method for the future direction of surface modifications of implants.

Enhanced Biotribological and Anticorrosion Properties and Bioactivity of Ti6Al4V Alloys with Laser Texturing

The poor biotribological properties and bioinertness of Ti6Al4V have restricted its application in biomedical materials. In this study, microgrooves of different widths were prepared on the surface of a Ti6Al4V alloy by laser treatment. The tribological properties under dry lubrication and simulated body fluid (SBF) lubrication conditions, the electrochemical corrosion properties in SBF solution, and the bone marrow mesenchymal stem cell (BMSC) behavior on the surfaces were systematically tested. The corresponding mechanisms were discussed. The results showed that Ti6Al4V with a microgroove width of 45 μm (Ti64-45) exhibited excellent wear resistance with decreasing wear rates of 89.79 and 85.43% under dry friction and SBF lubrication compared to the Ti64 sample, which might be due to the increase of surface microhardness. Moreover, the excellent anticorrosion performance of Ti64-45 was attributed to the grain refinement on the titanium alloy surface with a lower volume fraction ratio of β phase to α phase. In addition, the microgrooves with a width of 45 μm are more conducive to BMSC proliferation and adhesion, related to promoting cell signal transduction due to cell extrusion. These studies imply that the microgroove structures are potential for application in the medical field.

Study on the effect of surface characteristics of short-pulse laser patterned titanium alloy on cell proliferation and osteogenic differentiation

Concise, low-cost preparation of titanium alloy implants with high cell proliferation and osteogenic differentiation is urgently needed. Nanosecond laser ablation of titanium alloy has the advantages of short processing time, less pollution, and non-contact. In this research, we adopt a nanosecond UV laser to process the closed groove and cross groove titanium alloys with length to width ratio of 1:1, 2.5:1, 4:1, and 6:1. The surface morphology, surface roughness, phase, element distribution, surface chemistry, and wettability were characterized. The effect of the patterned surface's properties on the adhesion, proliferation, and osteogenic differentiation of stem cells was studied. The results show the laser-ablated lattice structure's surface energy can increase rapidly in the natural environment. The cell adhesion of stem cells on a lattice structure with low roughness and high surface energy is optimal. The element concentration at the ablated edges is higher than at the bottom under Marangoni and surface tension. Stem cells preferentially adhere to the ablated edges with high roughness, element concentration, and hardness. Cell differentiation is chiefly affected by patterning structure. On the surface of the boss structure with a length to width ratio of 2.5:1, the proportion of cell length to diameter is about 2.5, and the cell area is greater. The osteogenic differentiation of cells is the highest on the surface.

In vitro contact guidance of glioblastoma cells on metallic biomaterials

Cancer cells' ability to sense their microenvironment and interpret these signals for the regulation of directional adhesion plays crucial role in cancer invasion. Furthermore, given the established influence of mechanical properties of the substrate on cell behavior, the present study aims to elucidate the relationship between the contact guidance of glioblastoma cell (GBM) and evolution of microstructural and mechanical properties of the implants. SEM analyses of the specimens subjected to 5 and 25% of plastic strains revealed directional groove-like structures in micro and submicro-sizes, respectively. Microscale cytoplasmic protrusions of GBMs showed elongation favored along the grooves created via deformation markings on 5% deformed sample. Whereas filopodia, submicro-sized protrusions facilitating cancer invasion, elongated in the direction perpendicular to the deformation markings on the 25% deformed sample, which might lead to easy and rapid retraction. Furthermore, number of cell attachment was 1.7-fold greater on 25% deformed sample, where these cells showed the greatest cellular aspect ratio. The directional attachment and contact guidance of GBMs was reported for the first time on metallic implants and these findings propose the idea that GBM response could be regulated by controlling the spacing of the deformation markings, namely the degree of plastic deformation. These findings can be applied in the design of cell-instructive implants for therapeutic purposes to suppress cancer dissemination.

Characterization of the in Vitro Osteogenic Response to Submicron TiO2 Particles of Varying Structure and Crystallinity

Titanium oxide (TiO2) nano-/microparticles have been widely used in orthopedic and dental sciences because of their excellent mechanical properties, chemical stability, and ability to promote the osseointegration of implants. However, how the structure and crystallinity of TiO2 particles may affect their osteogenic activity remains elusive. Herein, we evaluated the osteogenic response to submicron amorphous, anatase, and rutile TiO2 particles with controlled size and morphology. First, the ability of TiO2 particles to precipitate apatite was assessed in an acellular medium by using a simulated body fluid (SBF). Three days after the addition to SBF, anatase and rutile TiO2 particles induced the precipitation of aggregates of nanoparticles with a platelike morphology, typical for biomimetic apatite. Conversely, amorphous TiO2 particles induced the precipitation of particles with poor Ca/P atomic ratio only after 14 days of exposure to SBF. Next, the osteogenic response to TiO2 particles was assessed in vitro by incubating MC3T3-E1 preosteoblasts with the particles. The viability and mineralization efficiency of osteoblastic cells were maintained in the presence of all the tested TiO2 particles despite the differences in the induction of apatite precipitation in SBF by TiO2 particles with different structures. Analysis of the particles' surface charge and of the proteins adsorbed onto the particles from the culture media suggested that all the tested TiO2 particles acquired a similar biological identity in the culture media. We posited that this phenomenon attenuated potential differences in osteoblast response to amorphous, anatase, and rutile particles. Our study provides an important insight into the complex relationship between the physicochemical properties and function of TiO2 particles and sheds light on their safe use in medicine.