Reeta Viitala

Cell viability in a wet silica gel

A modified two-step sol-gel route using silicon ethoxide (TEOS) has been used to synthesize amorphous sol-gel-derived silica, which has been successfully used as a cell encapsulation matrix for 3T3 mouse fibroblasts and CRL-2595 epithelial cells due to its non-toxicity. The sol-gel procedure comprised a first, low pH hydrolysis step, followed by a neutral condensation-gelation step. A high water-to-TEOS ratio and the addition of d-glucose as a porogen and source of nutrients were chosen to minimize silica dissolution and improve the biocompatibility of the process. Indeed, the cell integrity in the encapsulation process was preserved by alcohol removal from the starting solution. Cells were then added in a buffered medium, causing rapid gelation and entrapment of the cells within a randomly structured siloxane matrix in the shape of a monolith, which was maintained in the wet state. MTT and alamarBlue assays were used to check the cytotoxicity of the silica gels and the viability of entrapped cells at initial times in contact with silica. To improve cell attachment, cell clumping experiments - where groups of cells were formed - were designed, rendering improved viability. The obtained materials are therefore excellent candidates for designing tissue-culture scaffolds and implantable bioreactors for biomedical applications.

In Vitro Behavior of Yttrium Silica Sol-Gel Microspheres

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.

About Interactions Between Sol-Gel Derived Silica, Titania and Living Organisms

Sol-gel derived silica and titania have a specific interaction with many biological molecules, microbes, algae, cells and living tissue. The specific interactions mean that they differ from common reactions between non-viable materials and biomolecules or living tissues and the interactions are mostly beneficial from the viewpoint of biotechnical applications. Pepetides and proteins may preserve their activity and bacteria, algae and cells may preserve their viability and viruses their infectivity as encapsulated in sol-gel derived silica. Silica and titania are known to form a direct bond with living tissue which can be utilized in the biomaterial applications. Other application areas of silica and titania are in biosensing, tissue engineering, gene therapy, controlled delivery of therapeutic agents and environmental protection.

The Release and Bioactivity of Lysozyme from Selected Sol-Gel Derived SiO2 Matrices

Local drug release has many benefits – a steadier distribution, improved compliance, but most importantly it allows the convenient use of protein based molecules as therapeutic agents. Many different types of materials have been studied as drug carriers, including sol-gel derived SiO2 matrices. In this study lysozyme was used as a model protein and its release from prepared SiO2 monoliths and its biological activity thereafter was studied spectroscopically. Sucrose was used in some preparations to assess its ability to function as a protective agent during storing. Lysozyme release and bioactivity was similar in both preparations containing it when tested fresh. In monoliths stored for ten weeks, however, differences were observed in the biological activity of released lysozyme. In the preparations containing sucrose, lysozyme had retained its activity, while it was virtually nil in the preparations containing only lysozyme. This shows that sol-gel derived SiO2 matrices can be used as carriers for small proteins and that sucrose can function as a protective agent in them.

Refractive index sensing properties of long-period fibre grating with sol-gel derived coatings

Long-period fibre gratings (LPGs) have previously been used to detect quantities such as temperature, strain and refractive index (RI). The responsivity to surrounding refractive index means that, potentially, LPGs could be realised as optical biosensors for applications in biochemical and biomedical application areas. We report here to our best knowledge the first investigation on refractive index sensing properties of LPGs with sol-gel derived titanium and silicon oxide coatings. It is revealed that the RI sensitivity of an LPG is affected by both the thickness and the index value of the coating; the coating with higher index and thickness will enhance the LPG RI sensitivity significantly. The surrounding refractive index induced LPG resonance shift has been evaluated over the LPGspsila most sensitive RI region from 1.42 to 1.44. We have identified that, in this region, the uncoated LPG has an RI sensitivity of (-673.0 plusmn 0.4)nm/uri (unit of refractive index) while the LPG coated with titanium oxide exhibits a sensitivity as high as (-1067.15 plusmn 0.04)nm/uri.

Macrophage Induced Effect of Particulate Silica on Rat Mesenchymal Stem Cells In Vitro

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.