Response of human bone marrow stromal cells to a novel ultra-fine-grained and dispersion-strengthened titanium-based material.

A novel titanium-based material, containing no toxic or expensive alloying elements, was compared to the established biomaterials: commercially pure titanium (c.p.Ti) and Ti6Al4V. This material (Ti/1.3HMDS) featured similar hardness, yield strength and better wear resistance than Ti6Al4V, as well as better electrochemical properties at physiological pH7.4 than c.p.Ti grade 1 of our study. These excellent properties were obtained by utilizing an alternative mechanism to produce a microstructure of very fine titanium silicides and carbides (<100 nm) embedded in an ultra-fine-grained Ti matrix (365 nm). The grain refinement was achieved by high-energy ball milling of Ti powder with 1.3 wt.% of hexamethyldisilane (HMDS). The powder was consolidated by spark plasma sintering at moderate temperatures of 700 degrees C. The microstructure was investigated by optical and scanning electron microscopy (SEM) and correlated to the mechanical properties. Fluorescence microscopy revealed good adhesion of human mesenchymal stem cells on Ti/1.3HMDS comparable to that on c.p.Ti or Ti6Al4V. Biochemical analysis of lactate dehydrogenase and specific alkaline phosphatase activities of osteogenically induced hMSC exhibited equal proliferation and differentiation rates in all three cases. Thus the new material Ti/1.3HMDS represents a promising alternative to the comparatively weak c.p.Ti and toxic elements containing Ti6Al4V.

In vitro investigations of bone remodeling on a transparent hydroxyapatite ceramic.

The light microscopic examination of cells directly on bioceramic materials in the transmission mode is impossible because many of these materials are opaque. In order to enable direct viewing of living cells and to perform time-lapse studies, nearly transparent bioceramic materials were developed. A dense and fine-grained transparent hydroxyapatite (tHA) was processed by a gel-casting route followed by low-temperature sintering (1000 degrees C). By virtue of its transparency, direct visualization of cellular events on this material is possible in transmitted light. In this study, the interaction of different bone cell types with the tHA ceramic was envisaged. Investigation of rat calvaria osteoblasts (RCO) cultured on tHA by means of transmission light microscopy indicated good cytocompatibility of tHA. Microscopic analysis of osteogenic-induced human bone marrow stromal cells (hBMSC) on tHA and quantitative analysis of their lactate dehydrogenase (LDH) activity at different time points of culture revealed favorable proliferation as well. An increase of the alkaline phosphatase (ALP) activity indicated the differentiation of osteogenic-induced hBMSC towards the osteoblastic lineage. In addition, the differentiation of human monocytes to osteoclast-like cells could also be demonstrated on tHA and was confirmed by fluorescent microscopy imaging of multinucleated cells on the transparent material.