Development of Phosphatized Calcium Carbonate Biominerals as Bioactive Bone Graft Substitute Materials, Part I: Incorporation of Magnesium and Strontium Ions.

Synthetic materials based on calcium phosphate (CaP) are frequently used as bone graft substitutes when natural bone grafts are not available or not suitable. Chemical similarity to bone guarantees the biocompatibility of synthetic CaP materials, whereas macroporosity enables their integration into the natural bone tissue. To restore optimum mechanical performance after the grafting procedure, gradual resorption of CaP implants and simultaneous replacement by natural bone is desirable.

Development of Phosphatized Calcium Carbonate Biominerals as Bioactive Bone Graft Substitute Materials, Part II: Functionalization with Antibacterial Silver Ions.

Porous calcium phosphate (CaP) materials as bone graft substitutes can be prepared from Ca carbonate biomineral structures by hydrothermal conversion into pseudomorphic CaP scaffolds. The present study aims at furnishing such phosphatized Ca carbonate biomineral (PCCB) materials with antibacterial Ag ions in order to avoid perisurgical wound infections. Prior to this study, PCCB materials with Mg and/or Sr ions incorporated for stimulating bone formation were prepared from coral skeletons and sea urchin spines as starting materials.

Microstructures of Randall's plaques and their interfaces with calcium oxalate monohydrate kidney stones reflect underlying mineral precipitation mechanisms.

Randall's plaques (RP) are preferred sites for the formation of calcium oxalate monohydrate (COM) kidney stones. However, although processes of interstitial calcium phosphate (CaP) plaque formation are not well understood, the potential of plaque microstructures as indicators of CaP precipitation conditions received only limited attention. We investigated RP-associated COM stones for structural details of the calcified tissues and microstructural features of plaque-stone interfaces as indicators of the initial processes of stone formation.

Structure and composition of calcareous sponge spicules: a review and comparison to structurally related biominerals.

Since the early 19th century, the skeletons of calcareous sponges (Porifera: Calcarea) with their mineralized spicules have been investigated for their morphologies, structures, and mineralogical and organic compositions. These biomineral spicules, up to about 10mm in size, with one to four rays called actines, have various specific shapes and consist mainly of magnesium-calcite: in only one case has an additional phase of stabilized amorphous CaCO3 (ACC) been discovered. The spicules are invariably covered by a thin organic sheath and display a number of intriguing properties.

Nano-cluster composite structure of calcitic sponge spicules--a case study of basic characteristics of biominerals.

Spicules of calcareous sponges are elaborately shaped skeletal elements that nonetheless show characteristics of calcite single-crystals. Our atomic force microscopic and transmission electron microscopic investigation of the triradiate spicules of the sponge Pericharax heteroraphis reveals a nano-cluster structure with mostly well-aligned small crystal domains and pockets with accumulated domain misalignments. Combined high-resolution and energy-filtering transmission electron microscopy revealed carbon enrichments located in between crystal domain boundaries, which strongly suggests an intercalated network-like proteinaceous organic matrix.