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Objectives To systematically investigate the biological interface of Bio-Oss by analysing dissolution–precipitation behaviour and osteogenic responses using in vitro experimental systems.

Material and methods Different concentrations (1–100 mg/ml) of Bio-Oss were incubated in cell culture medium for 24 h before elemental concentrations for calcium, phosphorus and silicon in the medium were analysed with inductive coupled plasma-optical emission spectroscopy. Radioactive calcium-45 isotope labelling technique was used to study possible precipitation of calcium on the Bio-Oss particle. Biological interface of Bio-Oss was studied in osteogenic experiments using mineralization medium and three different sources of cells (primary mouse bone marrow stromal cells, primary rat calvarial cells and MC3T3-E1 mouse pre-osteoblast cell line). Cells were fixed and stained with Toulidine blue, von Kossa or Alizarin Red staining for confirmation of extracellular matrix mineralization.

Results Elemental analysis of the cell culture medium demonstrated a significant decrease of calcium and phosphorus and a dose-dependent release of silicon to the medium after incubation with Bio-Oss. A significant decrease of calcium and phosphorus in the medium occurred even at low concentrations of Bio-Oss. Uptake of calcium on the Bio-Oss particle was confirmed with radioactive calcium-45 isotope labelling technique. In osteogenic experiments with Bio-Oss (<1 mg/ml), matrix mineralization around the Bio-Oss particles were demonstrated in all three cell types with von Kossa and Alizarin Red staining.

Conclusion Dissolution–precipitation reactions occur at the surface of Bio-Oss, and osteogenic responses are seen at the biological interface. The concentration of Bio-Oss is a key factor for the experimental in vitro results, and may also have implications for the clinic.

Biomaterials are widely used in clinical practice as bone graft substitutes for treating patients with bone defects. A molecular level understanding of the chemical processes at the interface between the biomaterial and the biological environment is crucial to succeed in tissue regeneration and to predict the treatment outcome. In this study, we used three different bone graft substitute materials (BioGlass 45S5—synthetic, Bio-Oss—bovine derived and Algipore—derived from algae) which were incubated in an α-minimum essential medium (α-MEM) during 1, 3 and 7 days. Initial surface composition of the biomaterials and the chemistry of their solid–solution interface were monitored by XPS with a fast-frozen samples technique. The XPS analysis showed that the equilibrium at the solid-solution interface is reached within 24 h. The Na/Cl atomic ratio at equilibrium indicates a negatively charged surface for Bio-Oss. In contrast, the other two materials gained a positive surface charge, which resulted in pronounced adsorption of amino acids at the interface from the medium. The surface chemical reconstruction and charge generation mechanism responsible for this effect are discussed with regard to bulk composition of the materials and possible proliferation and differentiation cell patterns that could be expected at the interface. Copyright © 2010 John Wiley & Sons, Ltd.

These contribution books collect reviews and original articles from eminent experts working in the interdisciplinary arena of biomaterial development and use. From their direct and recent experience, the readers can achieve a wide vision on the new and ongoing potentials of different synthetic and engineered biomaterials. Contributions were not selected based on a direct market or clinical interest, than on results coming from very fundamental studies which have been mainly gathered for this book. This fact will also allow to gain a more general view of what and how the various biomaterials can do and work for, along with the methodologies necessary to design, develop and characterize them, without the restrictions necessarily imposed by industrial or profit concerns. The book collects 22 chapters related to recent researches on new materials, particularly dealing with their potential and different applications in biomedicine and clinics: from tissue engineering to polymeric scaffolds, from bone mimetic products to prostheses, up to strategies to manage their interaction with living cells.

Silicon containing materials are used in bone regeneration, and some of the materials, e.g. Bioactive glass 45S5 (BG), release silicon (Si) ions to the surrounding tissue after implantation. The role of Si in bone biology is debated; nevertheless findings suggest that Si is beneficial for bone formation. A majority of the experimental studies on Si and bone have focused on osteoblasts. The effects of Si on osteoclast formation and function have not been directly addressed. In the present study, we show that ionic dissolution extract from BG inhibit osteoclast bone resorption in an organ culture system as well as osteoclast formation in a mouse bone marrow system and in the RAW264.7 cell line. Si containing cell culture medium was prepared to address the issue whether or not the inhibitory effects with BG dissolution extract were Si ion dependent. The results suggest that the inhibitory effects of Si act directly on osteoclast precursors, by interactions with the RANK/RANKL/OPG signaling pathway as well as with gap junction intercellular communication. However, regulation via osteoblasts cannot be excluded. The inhibitory effect of Si on osteoclasts could be useful for future therapies or treating bone loss in patients, provided that molecular mechanisms are established.