Papers by Author: Reeta Viitala

Abstract: The role of silica and macrophages in fibrosis is well documented, but in bone formation it is relatively unknown despite decades of research with bioactive glasses. In this study macrophages were isolated from rat peritoneal and then cultured for five days in the presence of two types of silica microparticles with different solubilities. After the fifth day the culture medium was collected, purified and used as an additive in bone marrow derived rat stem cell cultures. The stem cells were cultured for five days in α-mem containing only 0,5% of FCS, enabling cell survival but disrupting their proliferation. As controls, stem cells were also cultured in α-mem containing silica microparticles. At days one and five the amount of soluble collagen was assayed from the culture medium and the cells were counted. All stem cell cultures with macrophage medium additives were found to be proliferative, with statistically significant difference to controls. However, collagen was only produced in cultures containing medium from macrophages cultured with fast-dissolving silica microparticles. This suggests that silica can induce cell proliferation and extra cellular matrix protein secretion which is mediated by macrophages, and that the solubility of silica is also a major factor in this reaction.

Abstract: Biodegradable silica microspheres containing neutron activable yttrium cations were investigated as a potential material for in situ radiotherapy of cancers. The sol-gel method used for preparing the microspheres allows obtaining at relative low temperatures materials of high purity and homogeneity, with controlled rate of biodegradability. The influence of yttrium on the biodegradability of the silica microspheres was studied in a simulated body fluid (SBF). The chemical durability of the microspheres was investigated under in vitro conditions and the concentration of yttrium released from the microspheres was determined.