Abstract
Multiphasic silica/collagen xerogels are biomaterials designed for bone regeneration. Biphasic silica/collagen xerogels (B30) and triphasic xerogels (B30H20 or B30CK20) additionally containing hydroxyapatite or calcite were demonstrated to exhibit several structural levels. On the first level, low fibrillar collagen serves as template for silica nanoparticle agglomerates. On second level, this silica-enriched matrix phase is fiber-reinforced by collagen fibrils. In case of hydroxyapatite incorporation in B30H20, resulting xerogels exhibit a hydroxyapatite-enriched phase consisting of hydroxyapatite particle agglomerates next to silica and low fibrillar collagen. Calcite in B30CK20 is incorporated as single non-agglomerated crystal into the silica/collagen matrix phase with embedded collagen fibrils. Both the structure of multiphasic xerogels and the manner of hydroxyapatite or calcite incorporation have an influence on the release of calcium from the xerogels. B30CK20 released a significantly higher amount of calcium into a calcium-free solution over a three-week period than B30H20. In calcium containing incubation media, all xerogels caused a decrease in calcium concentration as a result of their bioactivity, which was superimposed by the calcium release for B30CK20 and B30H20. Proliferation of human bone marrow stromal cells in direct contact to the materials was enhanced on B30CK20 compared to cells on both plain B30 and B30H20.
Highlights
The development of substitute materials for the restore and healing promotion of lost or wounded tissue is associated to a multiplicity of scientific and technical challenges
Structural investigations on multiphasic silica/collagen xerogels were performed by using transmission electron microscopy (TEM) and scanning electron microscopy (SEM)
In TEM analysis, silica was unambiguously detected by energy dispersive X-ray spectroscopy (EDX) signals of silicon (Si) and oxygen (O), hydroxyapatite by signals of calcium (Ca) and phosphorus (P) and calcite by EDX signals of Ca, carbon (C) and O
Summary
The development of substitute materials for the restore and healing promotion of lost or wounded tissue is associated to a multiplicity of scientific and technical challenges. The present study is focused on bio-inspired composites based on silica and collagen as biphasic materials as well as triphasic composites based on silica, collagen and a further mineral phase These composite materials for bone substitution are inspired by marine glass sponge spicules due to their excellent mechanical properties[7]. Our previous study, published by Heinemann et al, focused on the adjustment of mechanical properties in bone relevant ranges by variation of the xerogel composition[25] Another important property of bi- and triphasic silica/collagen xerogels is their bioactivity[26]. In contrast to calcium carbonate ceramics, the present study focuses on composite materials based on silica, collagen and calcite as a further mineral phase
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