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Weiguo Xu1, Cornelia Ganz2, Ulf Weber2, Martin Adam2, Gerd Holzhüter2, Daniel Wolter3, Bernhard Frerich3, Brigitte Vollmar1, Thomas Gerber21Institute for Experimental Surgery, 2Institute of Physics, 3Department of Oral, Maxillofacial and Plastic Surgery, University of Rostock, Rostock, GermanyAbstract: In clinical practice, vertebral compression fractures occur after trauma and osteoporosis. Kyphoplasty is a minimally invasive procedure using bone filler material for the treatment of such fractures. A full synthetic injectable bone substitute (SIBS) was manufactured by means of spray drying. The aim of this study was to characterize the SIBS and to analyze the remodelling process during degradation of the biomaterial and new bone formation after implantation. SIBS is an aqueous suspension of donut-like microparticles. These microparticles consist of nanocrystallites of synthetic hydroxyapatite embedded in amorphous silica gel. After implantation of SIBS in a proximal tibial diaphyseal defect in 52 rats, grafts were harvested for subsequent analysis on different days. Newly formed bone originating from endosteum was observed on day 6. Hematomas in the medullary space and cortical wounds disappeared on day 12. The wound region was completely replaced by a composite of newly formed cancellous bone, extracellular matrix, and SIBS. At day 63 the cortical defect was fully healed by bone, while newly formed bone in the medullary space almost disappeared and was replaced with bone marrow. In conclusion, SIBS demonstrated a unique structure with osteoinductive and bioresorbable properties, which induced fast bone regeneration. Therefore, a clinical application of SIBS for kyphoplasty is promising.Keywords: bone remodelling, electron microscopy, histomorphometry, nanotechnology, tissue engineering

Langmuir–Blodgett (LB) films of Cd arachidate and Ca arachidate with thicknesses of 1, 3, 9, and 25 layers were investigated using near edge x-ray absorption fine structure (NEXAFS spectroscopy), small angle x-ray scattering (SAXS), and reflected high energy electron diffraction (RHEED). The results from the x-ray diffraction experiments on layer thickness and interface roughness complement the structural information from NEXAFS on the average tilt angle of the alkyl chains in real space. The RHEED measurements confirm these findings and give additional information on the lateral order in these organic films. We find that the monolayer film shows a substantial degree of disorder, while for three and more LB layers, the molecular orientation is virtually identical to that of the corresponding fatty acid salts, i.e., the hydrocarbon chains are oriented perpendicular to the substrate surface in an all-trans conformation. Furthermore, a simplified and more robust analysis scheme for NEXAFS data obtained for hydrocarbon chains is presented. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate biomaterial degradation and new bone formation after implantation of a nanostructured hydroxyapatite (HA) grafting block. Furthermore, physical characteristics of the biomaterial were measured. The biomaterial consists of nanostructured HA embedded in a porous matrix of silica (SiO(2) ) gel. The blocks with two different contents of silica (group A: 24 wt % and group B: 39 wt %) were fixed with titanium screws at the lateral aspect of the mandible of minipigs (n = 5). The specific surface areas of both blocks were measured using Brunauer-Emmett-Teller (BET) equation and mercury intrusion. In all animals, the wound healing was uneventful. After 5 weeks, the biomaterial percentage was 51.5% ± 12.1% for group A and 33.2% ± 5.9% for group B (p = 0.017). New bone formation accounted to 7.6% ± 6.0% for group A and 15.3% ± 8.3% for group B (p = 0.126) after 5 weeks. After 10 weeks, further resorption of the biomaterial led to percentages of 30.6% ± 10.0% for group A and 12.1% ± 6.7% for group B (p = 0.000). After 10 weeks, new bone formations were measured to be 34.1% ± 10.8% in group A and 39.9% ± 13.5% in group B (p = 0.383). The rate of degradation of the biomaterial is controlled by the composition of the material. A higher content of silica gel matrix leads to faster degradation of the biomaterial. The formation of new bone failed to show a significant difference between both groups., (Copyright © 2010 Wiley Periodicals, Inc.)

A nanocrystalline bone substitute embedded in a highly porous silica gel matrix (NanoBone) has previously been shown to bridge bone defects by an organic matrix. As the initial host response on the bone graft substitute might be a determinant for subsequent bone formation, our present purpose was to characterize the early tissue reaction on this biomaterial. After implantation of 80 mg of NanoBone into the adipose neck tissue of a total of 35 rats, grafts were harvested for subsequent analysis at days 3, 6, 9, 12, and 21. The biomaterial was found encapsulated by granulation tissue which partly penetrated the implant at day 3 and completely pervaded the graft at day 12 on implantation. Histology revealed tartrate-resistant acid phosphatase (TRAP)-positive giant cells covering the biomaterial. ED1 (CD68) immunopositivity of these cells further indicated their osteoclast-like phenotype. Scanning electron microscopy revealed organic tissue components within the periphery of the graft already at day 9, whereas the central hematoma region still presented the silica-surface of the biomaterial. Energy dispersive X-ray spectroscopy further demonstrated that the silica gel was degraded faster in the peripheral granulation tissue than in the central hematoma and was replaced by organic host components by day 12. In conclusion, the silica gel matrix is rapidly replaced by carbohydrate macromolecules. This might represent a key step in the process of graft degradation on its way toward induction of bone formation. The unique composition and structure of this nanoscaled biomaterial seem to support its degradation by host osteoclast-like giant cells.

Accumulation of silica in marine organisms such as diatoms and sponges has been widely reported. The proteins depositing silica in these organisms have been identified and its structure has also been described. The ultrastructure of silica has not been studied in detail, however. Herein we describe the structure of silica in the spicules of the sponge Suberites domuncula. Peroxide treatment was performed to remove the organic compounds, thereby enabling a better study of the silica. Methods used for the study included scanning and transmission electron microscopy. Electron diffraction enabled structural comparison with silica glass at the atomic level. Small-angle X-ray scattering (SAXS) of the spicules was also conducted and structure correlation between these methods attempted. At a lower magnification, spicule needles with a smooth outer surface were visible. Diffraction results suggested a network-like structure in the spicules. Silica particles of 3 nm diameter could be measured by SAXS.

A German couple was struck by lightning. Both patients survived this event. Whereas the husband was unconscious for only a few minutes, his wife fell into coma for 24 h. The lightning stroke entered the body of the woman behind the left ear and left it at the left shoe. The stroke caused a partial evaporation of a gold ornamental chain on the neck, resulting in a tattoo of the neck skin. A biopsy of the skin 6 months after the event showed the accumulation of gold particles of different size in the dermis down to the subcutaneous fatty tissue. In semithin sections, histiocytes, multinucleated foreign giant cells, and fibroblasts were visible with uptaken metallic particles. In transmission electron microscopy, gold globules of up to 30 microm in diameter were visible outside the cells in the collageneous matrix of the connective tissue besides smaller metallic particles up to 5 nm inside lysosomes and residual bodies of phagocytic cells. Four different kinds of gold particles could be differentiated: globules, granular irregular particles, tubules, and tanglelike tracks. In scanning electron microscopy, gold particles were demonstrated by backscatter detection in the connective tissue of subcutis, where the EDX elemental analysis showed strong signals of aurum (Au), copper (Cu), and argentum (Ag). The detected metals were quantified by AAS as 70% gold, 21% silver, and 9% copper, which demonstrates the composition of gold alloy of the neck chain of the patient. Tanglelike tracks and elongated gold deposits represent crystals of gold salts, as detected by electron diffraction and polarization microscopy. Attempts to remove the gold particles from the skin to remove the tattoo should not be undertaken because the gold is deep and widespread.

Twelve patients underwent an osteosynthesis with titanium to treat upper and lower jaw fractures. Six to 12 months later, the miniplates were removed. Tissue samples were analyzed by light and electron microscopy for detection of a metallosis. The analysis showed new bone formation like callus tissue around the miniplates. In some cases small, rounded deposits and accumulation of colloid-like particles located next to bigger titanium artifacts were detected in the cytoplasm of histiocytes and in the matrix of connective tissue. The titanium was identified by elemental analysis using EDX in SEM as well as by EELS and electron diffraction in TEM. Both kinds of particles contain titanium, but they seem to be different in composition and derivation. The bigger particles seem to consist of metallic titanium and sourced by working on the metallic implants during the implantation itself. On the other hand, the colloidal-like, small, rounded particles in tissue macrophages and outside the cells in the matrix of connective tissue are presumably of other origin; for example, they could be derived from biodegradation and chemical conversion of the metallic implants. The titanium miniplates were examined before and after implantation by using ESCA technique and revealed metallic titanium and different compositions with other elements. The amount of titanium load of the tissue was very low in most cases and presumably not of biomedical relevance.