Effect of Different Density and Surface Modification of Titanium Clusters on the Adhesion and Growth of MG 63 Cells
Marta Vandrovcova Dpt. of Growth and Differentiation of Cell Populations
Institute of Physiology, Academy of Sciences of the Czech Republic
Czech Republic
Abstract:
Titanium, its oxides and alloys are considered to be convenient materials for construction of bone implants, particularly for the bone-anchoring parts of joint replacements. Titanium-based materials have a relatively low modulus of elasticity, and thus approach the elasticity modulus of the natural bone more closely than other metallic materials, such as stainless steel. No less important is the surface modification of the implanted materials, because the physical and chemical properties of the material surface, e.g. its roughness and wettability, play a decisive role for the cell-material interaction, and thus the integration of the implant with the surrounding bone tissue. It is known from literature that the optimal roughness for the adhesion and growth of bone cells should be approximately in tens of nanometers (measured by the Ra parameter). This beneficial effect of the nanoscale surface roughness is explained by the adsorption of cell adhesion-mediating proteins, such as vitronectin, fibronectin, collagen and laminin, in an appropriate spatial conformation for binding the active sites on these molecules by the cell adhesion receptors. In addition, surfaces with nanoscale irregularities were found to adsorb preferentially vitronectin, which is recognized mainly by osteoblasts [1]. The aim of this study was to test the influence of different density of nanoscale irregularities on the material surface on the adhesion, growth and potential immune activation of human osteoblast-like MG 63 cells in vitro. Nanoclusters of Ti (approximately 50 nm) were deposited on microscopic glass slides in two different densities, i.e. low (4 μg/cm2) and high (12 μg/cm2), and then they were covered by 25 nm or 80 nm of TiO2, which is known to support the cell adhesion and growth by its wettability [2]. Glass slides coated with a flat TiO2 film without underlying Ti clusters and standard cell culture polystyrene dishes were used as reference materials. The number of cells on the tested surfaces was evaluated in three time intervals (i.e., on days 1, 3 and 7 after seeding). The concentration of proteins participating in cell adhesion (β1-integrins, vinculin, talin) and cell immune activation (ICAM-1) was also measured by an enzyme-linked immunosorbent assay (ELISA) per mg of protein on day 7 after seeding. We found that the number of initially adhering cells (day 1) and the final cell population density (day 7) were the highest on the reference sample with flat TiO2 film. Also the concentration of β1-integrin adhesion receptors was the highest in cells on this sample. However, on day 7 after seeding, the cells on samples with low density of clusters covered by the thicker layer of TiO2 (80 nm) reached a higher population density than the cells on samples where the low-density clusters were covered with the thinner TiO2 film (25 nm), which was probably due to rounding and flattening the prominences on the material surface.
[1] Webster TJ, Ergun C, Doremus RH, Siegel RW, Bizios R: J Biomed Mater Res A, 51: 475-483, 2000
[2] He J, Zhou W, Zhou X, Zhong X, Zhang X, Wan P, Zhu B, Chen W: J Mater Sci Mater Med 19: 3465-72, 2008
Supported by the Academy of Sciences of the Czech Republic (Grant No. KAN101120701).
