bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical characteristics of functionally graded biodegradable implants for skull bone reconstruction
Authors: Wehmöller M. , Neuking K. , Epple M. , Annen T. , Eufinger H. 
Published: June 2006

AbstractA functionally graded implant was developed to substitute the function of the skull for geometry and for protection of the brain. The implant consists of polylactide/amorphous calcium phosphate as mechanically stable external structure and of polylactide/calcium carbonate as porous internal structure for the ingrowth of bone. For the examination of this protective mechanical function implant fragments were compared with bone fragments of the corresponding calvarium with a 3‐point bending test.
Silicon‐substituted hydroxyapatite ceramics (Si‐HAp): densification and grain growth through the prism of sintering theories
Authors: Putlayev V. , Veresov A. , Pulkin M. , Soin A. , Kuznetsov V. 
Published: June 2006

AbstractCeramics based on calcium phosphates is known to be a prospective material for biomedical applications. Noticeable attention is paid to hydroxyapatite Ca10(PO4)6(OH)2 (HAp) due to its affinity to a bone mineral. It was recognized recently that Si‐doped HAp is a highly promising material in sense of bioactivity improvement. In the frame of distinct research activity structured around this subject, some special problems are to be solved: (1) solubility of Si in the bulk of HAp lattice (and its limit) vs. segregation of Si to free surfaces and grain boundaries, (2) rationalization of Si effect on sintering of HAp ceramics, (3) charge compensation over aliovalent doping of HAp with Si and its interplay with thermal stability of HAp phase.The work was focused on a fabrication of Si‐HAp with Ca10(Po4)6‐x(SiO4)x(OH)2‐x (x=0..1) nominal composition and evaluation the effect of Si on sintering of HAp ceramics. The limit of Si solubility in HAp lattice was estimated to be not higher than x=0.1 in the formula above (at 1000 °C, according to XRD and SEM/EDX). The essence of the silicon influence consists in significant suppression of grain growth during the initial stage of sintering. Silicon doping reduces grain boundary mobility (increasing activation energy of lattice diffusion) along with the increase of pore mobility (in fact, increasing grain boundary diffusion). We believe that the effect of Si on sintering behaviour can be treated in terms of its segregation to grain boundaries, the phenomenon arising from a lattice instability of Si‐HAp due to the charge compensation in the course of aliovalent doping.
Deposition of functionalized calcium phosphate nanoparticles on functionalized polymer surfaces
Authors: Urch H. , Geismann C. , Ulbricht M. , Epple M. 
Published: June 2006

AbstractCalcium phosphate nanoparticles were functionalized using two polymeric additives: polyallylamine hydrochloride, PAH, giving them a positive charge, and polyacrylic acid, PAA, giving them a negative charge. These particles were deposited on surface‐functionalized polymers (polyethylene terephthalate track‐etch membranes; PET) by dip‐coating. If the charge of the nanoparticles and the charge of the polymer membrane had an opposite sign, efficient adsorption was observed, whereas on unfunctionalized polymer surfaces, no adsorption occurred.
The skeleton and pharyngeal teeth of zebrafish (Danio rerio) as a model of biomineralization in vertebrates
Authors: Neues F. , Arnold W. H. , Fischer J. , Beckmann F. , Gaengler P. , Epple M. 
Published: June 2006

AbstractZebrafish (Danio rerio) has become one of the most common models for genetics, and developmental research in the biosciences. Synchrotron radiation micro computer tomography (SRμCT), scanning electron microscopy, polarized light microscopy, and energy‐dispersive X‐ray analysis were applied to visualize the biomineralization in teeth and bones in high spatial resolution.
In vitro pH‐controlled calcification of biological heart valve prostheses
Authors: Krings M. , Kanellopoulou D. , Mavrilas D. , Glasmacher B. 
Published: June 2006

AbstractBackground: Bioprosthetic heart valves still suffer from calcification. In the department of Cryobiology & Biomaterials, we have established an in vitro calcification test method which is suitable for the investigation of calcification patterns of heart valves. In a modified test protocol we use the pH‐dependency of the calcification process to control and stabilise the process by keeping the calcification ions more constant than in the established test protocol. Methods: Five glutaraldehyde‐fixed porcine heart valve bioprostheses underwent accelerated dynamic in vitro calcification individually. Three valves were tested according to the established test protocol. Two valves were studied with the new pH‐controlled loop system. pH drop was used as an index for the consumption of the calcification ions. The degree of calcification was determined by means of μX‐ray (high resolution x‐ray on mammography machine), conventional and micro computer tomography (CT, μ‐CT). Results: We determined the average degree of calcification after 12 million cycles. The value was calculated to be 12 % vs. 67 % (established vs. pH‐controlled group) using μX‐ray (2D), 3 % vs. 16 % using CT, and 3 % vs. 33 % using μ‐CT. Conclusion: A new faster and more potent in vitro calcification method has been developed. Optimisation of this pH‐controlled method in order to implement an additional direct calcification ion concentration control is under construction.
Synthesis and characterization of DNA‐functionalized calcium phosphate nanoparticles
Authors: Sokolova V. , Prymak O. , Meyer‐Zaika W. , Cölfen H. , Rehage H. , Shukla A. , Epple M. 
Published: June 2006

AbstractCalcium phosphate nanoparticles were prepared by precipitation from aqueous solution. A stable colloid was formed by coating with DNA. The properties of the colloidal dispersion can be adjusted by variation of the inorganic nanoparticles. In particular, the partial substitution of calcium by magnesium or aluminum led to stable dispersions of nanoparticles. By a multi‐step precipitation process, it is also possible to include DNA into the particles in order to protect it from intracellular biochemical degradation. The dispersions were analyzed by dynamic light scattering, zeta potential measurements, analytical ultracentrifugation, and transmission electron microscopy.
Numerical computation of the porosity of bone substitution materials from synchrotron micro computer tomographic data
Authors: Vanis S. , Rheinbach O. , Klawonn A. , Prymak O. , Epple M. 
Published: June 2006

AbstractDifferent porous bone substitution materials were studied by synchrotron micro computer tomography (SRμCT). The digital data were analyzed with respect to the geometrical parameters of the samples, i.e., porosity, specific surface, and connectivity of the pores. For most samples (both from natural and synthetic sources), there is a truly interconnecting porosity, i.e., topologically, they contain only one single pore.
Magnesium‐substituted hydroxyapatite ceramics
Authors: Zyman Z. , Tkachenko M. , Epple M. , Polyakov M. , Naboka M. 
Published: June 2006

AbstractThe effect of the addition of magnesium (up to 10 wt%, expressed as MgO) on the phase composition, the microstructure and the mechanical properties of hydroxyapatite‐based ceramics (HA) was studied by X‐ray powder diffraction, infrared spectroscopy, scanning electron microscopy, and mechanical testing. Doping with magnesium did not change the crystal lattice of HA but, due to an isomorphous substitution of Mg2+for Ca2+, it caused a decrease in the average grain size, an increase of microporosity, a removal of the texture, and the formation of a weak intergranular boundary. The transcrystallite fracture pattern of pure HA was changed to a predominantly intercrystallite one. This resulted in a decrease in density (down to 2.93 g cm‐3), in microhardness (down to 400 MPa), in compressive strength (down to 190 MPa) and in improved plastic properties of the material (increasing the fracture toughness$ K_{1_C} $up to 2.7 MPa m1/2, close to that of the bone). It is interesting that the$ K_{1_C} $increase could be only observed for a small concentration of additives (up to 1 wt%), i.e. close to the Mg concentration in natural bone mineral.
Needs and trends for biomaterials and biodevices in oral and maxillofacial surgery
Authors: Muster D. , Meyer C. 
Published: June 2006

AbstractThe evolution of the devices used for the fracture fixation is now oriented toward the bioresorbable materials (PLA, PGA, PDX) which should gradually replace the metallic materials (titanium, SS) in the next 10‐15 years. The osteosynthesis devices will have to fulfil more precise biomechanical criteria, in certain anatomical zones (i.e. trapezoidal plates for the mandibular condyle).The most known TMJ prostheses are either definitive prostheses (no more available on the European market, only in the American market) or temporary condylar prostheses. In this field the lag compared with the orthopaedics is certainly over 20 years. Very few biomechanical studies have been performed and there is few interest from the industrials in Europe for this type of prostheses because of the small number of cases and the scarcity of the indications.Numerous materials of all classes have been tried as bone substitutes but all are lacking of osteoinductivity and therefore combined materials are largely studied. Actually, in maxillofacial surgery, the most used materials are HA, TCP, Coral eventually enriched with growth factors. Concerning tissue engineering, nice models are elaborated in various laboratories in the world but huge difficulties remain regarding the optimal molecular environment and the biomechanical functionality.
O‐phospho‐L‐serine modified calcium phosphate cements – material properties, in vitro and in vivo investigations
Authors: Reinstorf A. , Hempel U. , Olgemöller F. , Domaschke H. , Schneiders W. , Mai R. , Stadlinger B. , Rösen‐Wolff A. , Rammelt S. , Gelinsky M. , Pompe W. 
Published: June 2006

AbstractOne of the most important requirements for calcium phosphate bone cements (CPBC) is remodelling in vivo. Degradation of the artificial material and the formation of native new bone matrix have to interdigitate to avoid instability. The remodelling process should not last longer than one year. In this study a CPBC was modified with O‐phospho‐L‐serine (phosphoserine) to improve the material properties in order to speed up remodelling in vivo. The results showed that the modified cements exhibit a nano‐crystalline microstructure with a high specific surface area and increased compressive strength (about 50 %). Metabolic activity of osteoblasts was improved on the modified material. Monocytes were found to be highly activated on the cements containing phosphoserine. In addition the formation of multinucleated giant cells (osteoclast‐like cells) was not impaired on phosphoserine modified cement composites. In vivo experiments in Wistar rats and mini pigs clearly revealed that phosphoserine modified cements showed a higher capability of remodelling compared to the cements without phosphoserine.
A novel synthetic vascular prosthesis: effect of plasma protein adsorption on blood‐ and cyto‐compatibility
Authors: Knetsch M.L.W. , Aldenhoff Y.B.J. , Hanssen H.H.L. , Koole L. H. 
Published: June 2006

AbstractThe development of a genuinely functional small diameter vascular prosthesis remains one of the toughest problems in biomedical engineering. Most current small diameter vascular grafts fail because of thrombotic complications or neo‐intimal hyperplasia. Here were present a novel synthetic vascular prosthesis with a polymer coated luminal surface. The coating can be tuned for its hydrophilicity by varying the molar ratio of the monomers, N‐vinyl‐pyrrolidinone and butyl‐methacrylate. Additionally these polymeric coatings can be loaded with anticoagulant drugs, like heparin. Especially surface exposed heparin dramatically improved blood‐compatibility of the coating, reducing thrombin generation. For long‐term functionality of vascular prostheses, formation of an endothelial cell layer is vital. In vitro, the hydrophobic coatings in particular supported formation of an endothelial cell layer. Upon adsorption of blood plasma proteins, endothelial cells grew equally well on all surfaces, irrespective of the hydrophilicity. It was found that high density lipoprotein (HDL) is responsible for transforming hydrophilic coatings into good cell‐compatible surfaces. Furthermore, HDL can reduce surface‐induced thrombin generation and therefore can be used to modify the lumen of a vascular prosthesis.
Bioavailability and genotoxicity of soluble and particulate nickel compounds in cultured human lung cells
Authors: Schwerdtle T. , Hartwig A. 
Published: June 2006

AbstractNickel compounds are well known human and animal carcinogens, but the carcinogenic potential depends largely on the actual species. Within the present study, water soluble nickel chloride and poorly water soluble nickel oxide were compared with respect to uptake, intracellular distribution and genotoxicity as determined by the induction of DNA strand breaks and DNA base modifications recognized by the bacterial formamidopyrimidine DNA glycosylase (Fpg). The results show that both compounds were taken up by A549 cells. Furthermore, both compounds increase the nickel content in the nucleus and the cytoplasm yielding concentration ratios nucleus/cytoplasm of up to 0.18 and >0.5 for NiCl2 and black NiO, respectively. Also, the induction of DNA lesions was evident for water soluble and particulate nickel(II), even though pronounced effects were restricted to cytotoxic concentrations. Thus, it is proposed that nickel ions appear to be the ultimate species exerting both direct and indirect genotoxicity. The higher carcinogenic potential of particulate nickel(II) may thus be due to much longer retention times in vivo, not to different mechanisms of action on the cellular level.
The influence of foreign ions on the crystal lattice of hydroxyapatite upon heating
Authors: Zyman Z. , Rokhmistrov D. , Ivanov I. , Epple M. 
Published: June 2006

AbstractThe influence of foreign ions on the crystal lattice of hydroxyapatite (precipitated from aqueous solution by a conventional method at 96 °C with a given ratio of Ca/P=1.67:1) was studied during heating in air in the temperature range of 25‐1250 °C. The lattice constants decreased to those of stoichiometric hydroxyapatite by a complex dependence during heating. This dependence was correlated to a simultaneous release of gaseous products. These products resulted from the decomposition of foreign ions which were incorporated into the hydroxyapatite lattice during precipitation, i.e. ammonium, nitrate and carbonate. Stoichiometric hydroxyapatite with correct lattice constants was obtained at 1100 °C. Further heating to 1250 °C resulted in only minor changes in the lattice characteristics.
Anti‐infective surfaces based on tetraether lipids for peritoneal dialysis catheter systems
Authors: Frant M. , Stenstad P. , Johnsen H. , Dölling K. , Rothe U. , Schmid R. , Liefeith K. 
Published: June 2006

AbstractTo prevent bacterial growth on silicone catheters and other medical devices a new coating concept based on covalent immobilisation of a group of bipolar membrane spanning tetraether lipids from archaebacterium Thermoplasma acidophilum was developed. A lipophilic layer with optional further functionality was introduced to the surface of commercially available medical silicone elastomer slides and tubes. Physico‐chemical characterisation of the different surface modified polymers represents the basis for the optimisation of the monomolecular coatings. The new tetraether lipid coated catheter surfaces showed a successful reduction of bacterial adherence associated with an excellent biocompatibility.
Regulation of leukocyte adhesion molecules by leukocyte/biomaterial‐conditioned media: A study with calcium‐phosphate‐coated and non‐coated NiTi‐shape memory alloys
Authors: Köller M. , Esenwein St. A. , Bogdanski D. , Prymak O. , Epple M. , Muhr G. 
Published: June 2006

AbstractTo evaluate the role of soluble mediators released after interaction of leukocytes with biomaterials on cells of the implant microenvironment, the surface expression of adhesion molecules (CD11b, CD62L, CD66b, ICAM‐1) on freshly isolated whole blood leukocytes (WBL) was analyzed by flow cytometry after incubation in leukocyte/nickel‐titanium shape‐memory alloy (NiTi‐SMA)‐conditioned media. NiTi‐SMA samples were either coated with calcium phosphate by dipping in oversaturated calcium phosphate solution (CaP‐coating) or were non‐coated. Peripheral blood mononuclear cells (PBMC) and polymorphonuclear neutrophil leukocytes (PMN) were isolated and seeded on both samples to generate respective conditioned media. In comparison with conditioned media obtained by non‐coated NiTi‐SMA, the expression of CD11b, CD66b, and ICAM‐1 on WBL was upregulated by conditioned media obtained from CaP‐coated samples. In contrast, the expression of CD62L on WBL was decreased after incubation in conditioned medium obtained from CaP‐coated NiTi‐samples compared to non‐coated NiTi. These data demonstrate the possible influence of released mediators elicited by leukocyte‐biomaterial interactions on cells of the implant microenvironment.
The impact of nanocolloidal wear‐particles on human mononuclear cells
Authors: Podleska L. E. , Weuster M. , Dose E. , Kühne Chr. A. , Nast‐Kolb D. , Ruchholtz St. , Taeger G. 
Published: June 2006

AbstractThis article investigates the effects of metallic wear‐medium prepared from 316L stainless steel and titanium alloy (TiAl6V4) in vitro. Wear was generated by a tribometer, under sterile conditions, disc‐on‐pin submersed in cell culture medium. Wear medium was separated into a particle fraction (>200 nm) and a nanocolloidal fraction (< 200 nm). A standardized cell culture model was employed using isolated mononuclear cells from peripheral human blood cells were incubated with increasing amounts of wear medium containing particles or nanocolloids. Vitality was assayed using MTT and inflammatory reactions were measured by TNF‐α ELISA. In a second step wear‐medium was aged over two weeks in an incubator to simulate passivation of the implant / particle surfaces.Dose dependant toxic reactions induced by nanocolloids from titanium alloy and even more from stainless steel were identified with the vitality decreasing to 50 % compared to untreated cells. Nanocolloids did not induce inflammatory effects. Particles had no apparent toxic effects on cells. On the other hand, particles from titanium alloy induced a higher secretion of TNF‐α in the supernatants than 316L.Aged nanocolloids lost their toxic potential, but aged particles did still show a strong inflammatory reaction with titanium alloy being the stronger inflammatory agent.This study demonstrates that particles from titanium alloy can not be assumed as to be an inert biomaterial. In fact, titanium alloy particles induced a stronger inflammatory reaction rather than stainless steel. We conclude that both particles and nanocolloids show specific interactions with mononuclear cells in a sense of toxicity and inflammation. Furthermore, it seems to be of great importance to critically consider fabrication processes and age of particles used for cell culture settings in future research.
Inflammation in white matter: Clinical and pathophysiological aspects
Authors: Pleasure David , Soulika Athena , Singh Sunit K. , Gallo Vittorio , Bannerman Peter 
Published: June 2006

AbstractWhile the central nervous system (CNS) is generally thought of as an immunopriviledged site, immune‐mediated CNS white matter damage can occur in both the perinatal period and in adults, and can result in severe and persistent neurological deficits. Periventricular leukomalacia (PVL) is an inflammatory white matter disease of premature infants that frequently results in cerebral palsy (CP). Clinical and experimental studies show that both hypoxic/ischemic and innate immune mechanisms contribute to the destruction of immature oligodendroglia and of axons in the deep cerebral white matter in PVL. No data are yet available as to whether there is any genetic predisposition to PVL or to its neurological sequelae. Multiple sclerosis (MS) is an inflammatory white matter disease that often begins in young adulthood, causes multifocal destruction of mature oligodendroglia and of axons, and eventually leads to substantial cumulative neurological disability. Certain genetic polymorphisms contribute to susceptibility to MS, and adaptive immune responses to myelin‐associated self antigens, or to exogenous antigens that mimic these self antigens, play a central role in the pathophysiology of this disease. MRDD Research Reviews 2006;12:141–146. © 2006 Wiley‐Liss, Inc.
The Yin and Yang of cell cycle progression and differentiation in the oligodendroglial lineage
Authors: Nguyen Laurent , Borgs Laurence , Vandenbosch Renaud , Mangin Jean‐Marie , Beukelaers Pierre , Moonen Gustave , Gallo Vittorio , Malgrange Brigitte , Belachew Shibeshih 
Published: June 2006

AbstractIn white matter disorders such as leukodystrophies (LD), periventricular leucomalacia (PVL), or multiple sclerosis (MS), the hypomyelination or the remyelination failure by oligodendrocyte progenitor cells involves errors in the sequence of events that normally occur during development when progenitors proliferate, migrate through the white matter, contact the axon, and differentiate into myelin‐forming oligodendrocytes. Multiple mechanisms underlie the eventual progressive deterioration that typifies the natural history of developmental demyelination in LD and PVL and of adult‐onset demyelination in MS. Over the past few years, pathophysiological studies have mostly focused on seeking abnormalities that impede oligodendroglial maturation at the level of migration, myelination, and survival. In contrast, there has been a strikingly lower interest for early proliferative and differentiation events that are likely to be equally critical for white matter development and myelin repair. This review highlights the Yin and Yang principles of interactions between intrinsic factors that coordinately regulate progenitor cell division and the onset of differentiation, i.e. the initial steps of oligodendrocyte lineage progression that are obviously crucial in health and diseases. MRDD Research Reviews 2006;12:85–96. © 2006 Wiley‐Liss, Inc.
Astrocytes and developmental white matter disorders
Authors: Sen Ellora , Levison Steven W. 
Published: June 2006

AbstractThere is an increasing awareness that the astrocytes in the immature periventricular white matter are vulnerable to ischemia and respond to inflammation. Here we provide a synopsis of the articles that have evaluated the causes and consequences of developmental brain injuries to white matter astrocytes as well as the consequences of several genetic mutations that result in abnormal astrocyte development. Emerging data suggest that the astrocytes are not simply responding to the injury but are likely victims as well as culprits. Given the important roles that astrocytes play in maintaining ionic, neurotransmitter, and metabolic homeostasis in the brain, a more thorough understanding of the mechanisms that lead to their incapacitation, demise, or reactions as well as a better understanding of the stimuli that regulate their neuroprotective and regenerative properties will enable these cells to be manipulated to preserve the integrity of white matter and to potentially provide therapeutics to enhance neonatal regeneration and recovery from brain injury. MRDD Research Reviews 2006;12:97–104. © 2006 Wiley‐Liss, Inc.