Calcium and phosphate adsorption as initial steps of apatite nucleation on sol-gel-prepared titania surface

How Surface Properties of Silica Nanoparticles Influence Structural, Microstructural and Biological Properties of Polymer Nanocomposites

The aim of this work was to study effect of the type of silica nanoparticles on the properties of nanocomposites for application in the guided bone regeneration (GBR). Two types of nanometric silica particles with different size, morphology and specific surface area (SSA) i.e., high specific surface silica (hss-SiO₂) and low specific surface silica (lss-SiO₂), were used as nano-fillers for a resorbable polymer matrix: poly(L-lactide-co-D,L-lactide), called PLDLA. It was shown that higher surface specific area and morphology (including pore size distribution) recorded for hss-SiO₂ influences chemical activity of the nanoparticle; in addition, hydroxyl groups appeared on the surface. The nanoparticle with 10 times lower specific surface area (lss-SiO₂) characterized lower chemical action. In addition, a lack of hydroxyl groups on the surface obstructed apatite nucleation (reduced zeta potential in comparison to hss-SiO₂), where an apatite layer appeared already after 48 h of incubation in the simulated body fluid (SBF), and no significant changes in crystallinity of PLDLA/lss-SiO₂ nanocomposite material in comparison to neat PLDLA foil were observed. The presence and type of inorganic particles in the PLDLA matrix influenced various physicochemical properties such as the wettability, and the roughness parameter note for PLDLA/lss-SiO₂ increased. The results of biological investigation show that the bioactive nanocomposites with hss-SiO₂ may stimulate osteoblast and fibroblast cells’proliferation and secretion of collagen type I. Additionally, both nanocomposites with the nanometric silica inducted differentiation of mesenchymal cells into osteoblasts at a proliferation stage in in vitro conditions. A higher concentration of alkaline phosphatase (ALP) was observed on the material modified with hss-SiO₂ silica.

Effect of crystallographic phases of TiO2 on hepatocyte attachment, proliferation and morphology

In this study, the effect of the crystallographic phases of titanium dioxide (TiO(2)) on hepatocyte response was investigated by culturing cells in a medium containing a dissolution of rutile TiO(2) powders, and on anatase and rutile ceramic discs. When the concentration of Ti ions exceeded 0.16 microg/mL, TiO(2) exhibited cytotoxicity. However, in a range of concentrations between 10(-6) and 10(-3)microg/mL, the Ti ion leached out from the powder stimulated cell proliferation. Cytocompatibility was also examined by the cell attachment and proliferation on the TiO(2) discs. The results show that the surface characteristic of the TiO(2) discs was the main factor influencing cell attachment, and the cells were better attached on the dense surface of the discs with high crystallinity than on the loose surface with low crystallinity. Both the surface characteristic and the crystallographic phase affected cell proliferation. In addition to the dense surface with high crystallinity, the anatase ceramics was in favor of cell proliferation as compared to the rutile ceramics sintered at the same temperature. In conclusion, the results suggest that the dense rutile ceramic with high crystallinity is a good substrate for hepatocytes.

Evaluation of calcium titanate as apatite growth promoter

Calcium titanate (CaTiO(3), perovskite) has been used to determine its apatite nucleation ability and propose a possible nucleation initial step. Measurements of calcium leaching from the calcium titanate surface and phosphate adsorption experiments were carried out separately by using commercial calcium titanate suspensions at room temperature. Adsorption behaviour determined by zeta potential measurements shows that phosphate is strongly adsorbed on the calcium titanate surface. It was found that the higher the pH, the higher the Ca present on the calcium titanate surface, but phosphate adsorption followed this trend only up to pH 7.4. Results suggest that phosphate ions are not adsorbed only on Ca sites but also on TiO(2) groups sites of the surface, formed after calcium leaching from the surface. When both ions are simultaneously added in a modified simulated body fluid containing calcium titanate, at 37 degrees C, apatite growth occurs on its surface after 1 week of immersion.