bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of surface zeta potential and substratum chemistry for regulation of dermal fibroblasts interaction
Authors: Altankov G. , Richau K. , Groth Th. 
Published: January 2004

AbstractSynthetic materials considered for biohybrid skin or other tissue engineering applications have to support cellular interaction and colonisation of implants. However, despite the number of studies reported in the literature, there is no agreement on the principal factors applicable to modulate the interaction with cells, such as the wettability of biomaterials, their surface potential and chemistry of the surface. Particularly, in this study we were interested on the impact of surface chemistry and net surface (zeta) potential on dermal fibroblasts. To address this question self assembled monolayers of silanes on glass, further derivatized with different functional groups, were used to study the adhesion and proliferation of human skin fibroblasts in response to these factors. The model surfaces were characterized using streaming potential (zeta potential) and water contact angle measurements. All samples were found to be negatively charged at physiological pH (regardless of the different chemistry) increasing (or equal ∼) the magnitude of the negative potential in the following order: hydroxy (OH) < amine (NH2) ∼ epoxy (EPOXY) < carboxyl (COOH) < three‐fluorocarbon (CF3) < sulfonic (SO3) functionalities. The interaction of fibroblast characterized by the effectiveness of cell adhesion, spreading and actin stress fibres formation decreased almost in the opposite order: NH2 > OH > EPOXY > SO3 > COOH > CF3 functions. The surfaces were found also to be highly wettable, except CF3. Interestingly, the best cellular interaction was found on the moderately wettable NH2 surface representing water contact angle (CA) of 65°, and the worst, on the least wettable CF3 surface (CA 85°) indicating that not only the surface potential but also the type of functional groups may play an important role. The organisation of α5 and β3 integrins generally followed the same trend of less clustering in focal adhesion plaques when the negative potential increased, except on SO3 surface, where β3 but not α5 integrins were greatly expressed. Cell growth however, showed a significant decrease on highly charged COOH and SO3 surfaces, as well as, on non‐polar CF3 functions. The best proliferation response was obtained on surfaces with primary amine groups. The results indicate that the surface (zeta) potential might be a critical parameter for cellular interactions, but also the substratum wettability and the type of functional groups have to be controlled in order to improve the biocompatibility of material surfaces.
In‐vitro preparation of nanocrystalline calcium phosphates as bone substitution materials in surgery
Authors: Tadic D. , Veresov A. , Putlayev V.I. , Epple M. 
Published: January 2004

AbstractA continuous preparation method for nanoscopic calcium phosphate ceramics is presented. The influence of processing parameters (temperature, time) on the properties of calcium phosphates was studied. Crystallinity, structure, and morphology are important for an application as biodegradable implant material in bone contact. The samples were studied in detail using X‐ray powder diffraction, infrared spectroscopy, atomic absorption spectroscopy, photometry, scanning electron microscopy, and transmission electron microscopy. All calcium phosphate precipitates are non‐stoichiometric, calcium‐deficient hydroxyapatites.
Statistical Mechanical Modeling of Protein Adsorption
Authors: Van Tassel P. R. 
Published: January 2004

AbstractWe present rationale for and a derivation of a statistical mechanical model of protein adsorption. Proteins are modeled as rigid geometric objects adsorbing initially in a reversible manner and subsequently undergoing an irreversible change in shape to a permanently adsorbed state. Both adsorption and shape change occur subject to energetic interactions with previously adsorbed proteins. We evaluate the model quantitatively for proteins with disk‐shaped projections within the scaled particle theory and compare the predictions to experimental measurements taken via optical waveguide lightmode spectroscopy.
Biomaterials for ossicular chain reconstruction. A review
Authors: Neumann A. , Jahnke K. 
Published: January 2004

AbstractThis review gives a survey of biomaterials used for ossicular chain reconstruction. The survey is focussed on application, biophysical requirements, properties and goals for future developments. The implantation site middle ear differs from others due to aeration and potential bacterial colonization. As a consequence, implant materials must exhibit excellent biocompatibility, biostabilty and sound conducting properties. In vitro and in vivo biocompatibility investigations and clinical observations determine the choice of material. Additionally the implants must provide the possibilty of intraoperative shaping or should be available in different variations in order to allow reconstruction appropriate to the individual conditions. Ceramics, metals and plastics are materials in current use. Based on thorough experimental and long term clinical experiences, the bioinert aluminum oxide is favorable amoung the ceramics. Bioactive ceramics may have minor biostability and the risk of fixation to surrounding bone which impairs sound conduction. This is also true for hydroxyapatite although biodegradation occurs only rarely. Today, titanium is the metal best established in middle ear implantation, reflected by excellent biocompatibility in vitro and in vivo, and good clinical results. Titanium is preferred by many surgeons, considering that sound transmission properties are mainly dependent on the implant weight. In stapes surgery, when the implant has direct contact to inner fluids, gold was accused to cause granuloma formation with subsequent inner ear damage in selected cases. In frequent past and present use, plastics (porous polyethylene and teflon) have proven to be of limited value in ossicular chain replacement because of high extrusion rates and the observation of material desintegration and bacterial colonization. In order to individually manage the pathological conditions in the middle ear, the implant design is of crucial importance. It is dependent on the ossicle to be replaced and the implant material. Future investigations have to minimize implant extrusions possibly by modifying and improving implant surfaces.
Laser‐Raman and Nuclear Magnetic Resonance (NMR) studies on plasma‐sprayed hydroxylapatite coatings: Influence of bioinert bond coats on phase composition and resorption kinetics in simulated body fluid
Authors: Heimann R. B. , Tran H. V. , Hartmann P. 
Published: January 2004

AbstractThe structure and phase composition of HAp coatings deposited onto Ti6Al4V coupons (50x20x2mm) by atmospheric plasma spraying (APS) were studied by laser‐Raman spectroscopy, 31P‐ and 1H‐MAS‐NMR and 2D‐31P/1H HETCOR‐CP‐NMR spectroscopy, and XRD with Rietveld refinement. The samples investigated comprised APS HAp coatings with and without a TiO2 bond coat as well as coatings incubated for different lengths of time (up to 12 weeks) in simulated body fluid (SBF) under physiological conditions. In APS coatings the presence of a bond coat increased the proportion of well‐ordered crystalline HAp at the expense of distorted apatite‐like structures such as oxyHAp and oxyapatite, and thermal decomposition products such as tricalcium phosphate (TCP) and tetracalcium phosphate (TTCP), and also decreased the amount of amorphous calcium phosphate (ACP). Incubation in SBF further advanced the proportion of crystalline HAp since the disordered structures, the thermal decomposition products, and ACP exhibit substantially higher solubility.
Surface modification of a novel porous titanium dioxide/glass composite
Authors: Erli H. J. , von Walter M. , Ragoß C. , Steffens G. C. M. , Paar O. , Maier H. R. 
Published: January 2004

AbstractA novel technique is used to produce an open porous titanium dioxide/glass composite, named Ecopore, with promising structural and biological properties for the development as a bone graft. This study aims at a fast and lasting integration of the new material by means of biochemical surface modification. Surface etching of Ecopore, aminosilanization and covalent coupling of the cellular attachment mediator fibronectin was employed as modification strategy. In a comparison of different etching procedures, alkaline etching led to the highest density of amino functions after subsequent aminosilanization. Fibronectin was immobilized using a bifunctional aminoreactive PEG‐linker. This protein coating improved the attachment of human osteoblast‐like cells (HOB) on non‐porous Ecopore as displayed by vital staining. XTT metabolism assays indicated an enhanced HOB growth in the initial phase of cultivation on fibronectin‐coated versus non‐coated specimens. In a first feasibility study, cultivation of HOB on coated porous Ecopore cylinders with a median pore size diameter of 130 μm showed that cellular growth was uniform and dense on the external surface of the specimen, but was sparse in the interior pore system. Ecopore batches with larger pores will be modified and investigated in vitro and in vivo in the next step of the study.
Nano‐porous Alumina Coatings for Improved Bone Implant Interfaces
Authors: Walpole A. R. , Briggs E. P. , Karlsson M. , Pålsgård E. , Wilshaw P. R. 
Published: January 2004

AbstractA new method is proposed for coating implants that produces a metal implant covered in a layer of nano‐porous alumina ceramic. These layers are produced by first depositing a layer of aluminium on the implant surface and then anodising it in phosphoric acid to produce the nano‐porous structure. This process results in the conversion of the aluminium to alumina containing 6‐8wt% phosphate ions. The surface alumina layer is bonded to the substrate via an interfacial layer of fully dense anodised titanium oxide. Mechanical measurements have shown that the shear and tensile strength of this coating are in excess of 20MPa and 10MPa, respectively.The biological performance of nano‐porous alumina material has been assessed and shown to be highly favourable, supporting normal osteoblastic activity and maintaining the osteoblastic phenotype. The filling of the nano‐porous coating with bioactive material to achieve enhanced biological performance has been investigated using colloidal silica as an analogue for a Bioglass sol. The coating has been loaded with silica by dipping in colloidal silica with a pH of 5.6. Pore filling equivalent to 1.3 wt% SiO2 in the coating as a whole has been achieved in this way.
A TiO2‐Binding Protein isolated from Rhodococcus Strain GIN‐1 (NCIMB 40340) – Purification, Properties and Potential Applications
Authors: Gertler G. , Brudo I. , Kenig R. , Fleminger G. 
Published: January 2004

AbstractA Rhodocuccus strain (Rh. GIN1, NCIMB 40340), which is capable of adsorption to titanium dioxide (TiO2) and TiO2‐containing coal fly ash particles, has been isolated previously in our Lab. Selectivity experiments showed that the bacterium is capable of adsorption to other metal oxides as well (e.g. magnetite and Al2O3) but at lower affinities. The bacterium binds tightly both to rutile and anatase TiO2. In electronmicrograms the formation of “bridge‐like” structures between the bacterium and the oxide is observed. A specific protein fraction, located on the cell wall of the bacterium was isolated from the bacterium. This protein was found to adhere strongly to TiO2 particles at high salt concentrations, similarly to the binding to TiO2 of the intact bacteria. TiO2 (rutile) was found to bind the protein faster, stronger and at a higher capacity than the anatase isoform. The 55 kDa Ti‐Binding Protein (TiBP) was isolated from the bacteria after homogenization by French Press. It was purified by affinity chromatography on TiO2 particles, hydrophobic chromatography on a Fractogel‐propyl column and gel filtration on a Superdex G‐200 column. The same protein was isolated from the bacteria by treatment with mutanolysin, an enzyme which is commonly used to retrieve cell‐wall proteins from Gram‐positive bacteria, demonstrating the outer cell location of the protein in Rh. GIN1. TiBP exhibits metal oxide binding selectivity similar to that of the intact bacterium, namely TiO2>ZnO>Al2O3 >Fe2O3(magnetite). Hydrophobic forces seem to dominate the interactions of the protein with TiO2 as its binding capability is greatly enhanced in the presence of high concentrations of NaCl and its desorption requires high concentrations of urea and SDS. These features differentiate TiBP from other proteins known to adsorb TiO2 (such as hemoglobin, cytochrome c and bovine serum albumin), mainly by weak, charge‐based interactions.
Stability of Surface‐Enhanced Ultrahydrophilic Metals as a Basis for Bioactive rhBMP‐2 Surfaces
Authors: Chatzinikolaidou M. , Zumbrink T. , Jennissen H. P. 
Published: January 2004

AbstractFor several years the treatment of metals like cp titanium and 316L stainless steel with concentrated chromosulfuric acid at high temperatures (230‐240 °C) has formed the basis for preparing ultra‐hydrophilic priming coats on these metals (Jennissen et al. Materialwiss. Werkstofftech. 30, 838‐845, 1999). Metals treated in this way have been called surface‐enhanced, displaying a characteristic ultrastructure, and can be easily modified to carry a biocoat of recombinant human bone morphogenetic protein 2 (rhBMP‐2). The major oxide on surface enhanced titanium is TiO2. Thus this TiO2‐layer could be responsible for the ultra‐hydrophilic properties of the priming coat. Irradiation of TiO2 layers by ultraviolet light (Wang et al., Nature 388, 431‐432, 1997) has been shown to endow these layers with ultra‐hydrophilic properties (i.e. contact angles of ∼ 0°). However the ultra‐hydrophilic TiO2‐layers produced by irradiation are unstable and revert to the original high contact angles of ∼ 70° within several days. The question of whether the ultra‐hydrophilic surfaces prepared by the chromosulfuric acid method show long‐term stability was therefore important to answer. In addition the question if rhBMP‐2 immobilized on such a surface will retain its biological activity was of great interest. In this paper it will be shown that ultrahydrophilic titanium mini‐plates retain their ultra‐hydrophilicity with contact angles of 0‐8° unchanged for at least 50 days and support the immobilization of rhBMP‐2 in a biologically active form.
Identification of the anthelix motif in the TGF‐β superfamily by molecular 3D‐Rapid Prototyping
Authors: Laub M. , Jennissen H. P. 
Published: January 2004

Abstract3D‐Rapid Prototyping (3D‐RP) is a novel technique for the construction of highly accurate three‐dimensional polyamide models of biomolecules. This method has been shown to be a valuable tool in the modeling of protein‐protein‐interactions as well as in the analysis of surface topography. Using this technique we were recently able to identify a so far unknown structure on the concave side of bone morphogenetic protein 2 (BMP‐2). Since this structure is the imprint of a left‐handed helix we have called this negative an unthelix. Obviously this novel structural feature of BMP‐2 may act as a binding side for endogenous ligands.BMP‐2 belongs to the highly conserved Transforming Growth Factor‐β (TGF‐β) superfamily, a large group of multifunctional peptides controlling differentiation, proliferation and repair in multicellular organism. The protomer structures of all members share a cystine‐knot motif as a characteristic feature. The question therefore arose whether a) the novel anthelical motif found in BMP‐2 is a common structural feature of this family and b) if there are any differences in terms of pitch and radius of the anthelix. As anthelical structures are difficult to visualize and nearly impossible to quantify using 3D molecular visualization software we constructed models of BMP‐2, BMP‐7 and TGF‐β2 from X‐ray crystallographic data by 3D‐Rapid Prototyping (3D‐RP).The anthelix motif was found in BMP‐2, BMP‐7 and TGF‐β2 with similar values for pitch (ca. 8‐10 nm) and radius (ca. 0.5‐0.7 nm). In contrast the anthelical motif was not found in a 3D‐RP model of human chorionic gonadotropin (HCG) which is also a member of the cystine‐knot family but doesn’t belong to the TGF‐β superfamily. These results were corroborated by measurements of the intersubunit angle of these dimeric proteins (141‐149°) and the distances between the center of mass (1.68‐1.96 nm) of the subunits both of which appear to be determinants of the anthelical pitch.We conclude that the anthelical groove on the concave side is a common structural motif of BMP‐2, BMP‐7 and TGF‐β2 and maybe of the whole group of the TGF‐β superfamily.
Modified cemented stem fixation in hip arthroplasty with computer based analysis – Experimental results
Authors: Barden B. , Weßkamp B. , Löer F. , Michiels I. 
Published: January 2004

Abstract27 cemented stems were implanted in fresh‐frozen human cadaver femora with third generation antegrade cementing technique and with prechilled vacuum‐mixed and pre‐pressurized Palacos R bone cement. 3 groups with different implantation techniques were compared according to the achieved cement mantle thickness distribution. Group 1 (modified stem fixation): 7 canulated stems inserted over guidetubes that were fixed in distal synthetic plugs (3 Willert CF‐30 and 4 flanged Charnley stems). The guidetubes served simultaneously for stem centralization and evacuation of the intramedullary cavity. Group 2: 12 stems with distal centralizers with fins (4 flanged Charnley, 8 anatomic cemented AC), and Group 3: 8 stems without centralizer (4 Willert CF‐30 and 4 flanged Charnley). For analysis, each femur was cut into mean 25 cross‐sections (range, 22 ‐ 31). Contact radiographs were taken and digitized with a sampling distance of 0.12mm (204.8 dpi). Using a custom‐made computer program (FemStat 1.001), the cement mantle thickness was determined at mean 650 implant surface points per cross section. Results: The percentage of critical cement mantle thickness was lower for the canulated stems with guidetube. Here 14.1 % of the measurements were smaller than 2mm. For the stems with distal centralizer and without centralizer this was 28.3 % and 28.2 % (p = 0.003 and p = 0.002, U‐test). Cement mantles smaller than 1mm were also reduced for group 1 (2.8 % compared with 4.7 % and 7.5 %) but this was not significant (p = 0.384 and p = 0.094). The stems without centralizers had only slightly inferior cement mantles if compared to stems with distal centralizers with fins (for < 2mm p = 0.571, for < 1mm p = 0.305). Comparing different cementing techniques for one constant type of prosthesis (Charnley) the canulated stems with guide tubes provided a significantly better cement mantle thickness than the stems with distal centralizers (for < 2mm 10.3 % compared with 26.6 %, p = 0.029; for < 1mm 1.5 % compared with 3.4 %, p = 0.343). Distal centralizers failed, as the intramedullary cavity is elliptic in cross section and the gaps between the wings caused malposition. For all stems in group 3 improvement of the cement mantle thickness was predominantly achieved in the distal and middle third of the femur. Conclusion: The implantation technique with canulated stems inserted over a guidetube allows superior stem positioning leading to a more favourable cement mantle.
Biological Multi‐layer Systems as Implant Surface Modification
Authors: Willumeit R. , Feyerabend F. , Kamusewitz H. , Schossig M. , Clemens H. 
Published: January 2004

AbstractIn living organisms the natural contact areas between cells are the cell membranes. These membranes separate the individual cells or build reaction compartments in an aqueous environment. Beside their structural role they also have specific functions that are due to the great variety of their components which are lipids (about 40 %) and proteins (about 60 %).In terms of implant development the next neighbors of the cells are artificial materials which do not belong to the natural cellular environment. Therefore, a biocompatible implant surface is needed which is achieved by either the correct choice of the material and surface roughness or a functionalization of the surface.To date little is known of the role lipids could play in this context. However, from literature we know that phospholipids can cause calcification and that modified phosphorylcholine polymers ('MPC polymers') are used to decrease cell adhesion and to improve blood compatibility. In the last few years it became obvious that the lipid contribution in the membrane is not only important as support for proteins but that the lipid membrane itself can also be a target for drug design and its structure can influence the function of the proteins. We therefore focused our interest on this class of amphiphilic molecules. In this work we present initial observations on the modification of metallic implant surfaces of Ti‐6Al‐7Nb (in mass percent) by phospholipid multilayers, using contact angle measurements and surface sensitive characterization techniques such as scanning electron microscopy (SEM) and scanning force microscopy (SFM). Preliminary data concerning cell adhesion experiments are also presented.
Wirkungs‐ und Resistenzmechanismen: Was ist neu an Ketoliden und Oxazolidinonen?
Authors: Heisig Peter 
Published: January 2004

AbstractMit Ketoliden und Oxazolidinonen stehen seit kurzem zwei neue Antibiotikaklassen zur Verfügung, die zur Behandlung von Atemwegsinfektionen und Infektionen durch resistente grampositive Erreger eingesetzt werden. Beide greifen an jeweils anderen Stellen im bakteriellen Ribosom an und hemmen die Proteinsynthese. Dabei zeigen sie einen bakteriostatischen Wirkungstyp. Fortschritte in der Aufklärung der 3D‐Struktur des Ribosoms haben detaillierte Vorstellungen zu den molekularen Wirkungs‐ und Resistenzmechanismen dieser neuen Wirkstoffklassen erbracht, die für eine Weiterentwicklung beider Klassen eine wichtige Voraussetzung darstellen.
Zur Pharmakokinetik von Linezolid und Telithromycin: Zwei neue Antibiotika mit besonderen Eigenschaften
Authors: Sörgel Fritz , Landersdorfer Cornelia , Bulitta Jürgen 
Published: January 2004

AbstractMit Linezolid und Telithromycin stehen zwei neue Antibiotika zur Verfügung, die sich in ihren pharmakokinetischen Eigenschaften von anderen Substanzklassen unterscheiden. Beim Linezolid fällt auf, dass es trotz seiner chemisch eher neutralen Eigenschaften sehr gut in Gewebe penetriert und ansonsten aufgrund seiner vollständigen oralen Resorption, seiner parenteralen Applizierbarkeit und seiner bisher nicht bekannten Neigung zu pharmakokinetischen Interaktionen eine gut überschaubare Substanz darstellt.Telithromycin zeigt sich als eine konsequente Weiterentwicklung aus dem Bereich der Makrolide, die zu besonderen pharmakokinetischen Eigenschaften geführt hat. Hier stehen ebenfalls sehr gute Penetrationseigenschaften in das Gewebe und die mittel bis lange Halbwertszeit im Vordergrund. Diese erlaubt eine einmal tägliche Dosierung.Zusammen mit den antimikrobiellen Eigenschaften stellen diese beiden Substanzen eine wichtige Erweiterung des antibiotischen Arzneimittelschatzes dar.
Linezolid in der Therapie: Wirkung bei nosokomialer Pneumonie und schweren Haut‐ und Weichteilinfektionen
Authors: Bodmann Klaus‐Friedrich 
Published: January 2004

AbstractZusammenfassend ist festzustellen, dass Linezolid unter Berücksichtigung der heutigen Studienlage bei schweren Haut‐und Weichteilinfektionen dem Vancomycin wenigstens gleichzustellen ist. Bei durch MRSA verursachter nosokomialer Pneumonie ist Linezolid als Mittel der ersten Wahl anzusehen, da statistisch signifikant höhere Heilungsraten und niedrigere Letalitätsraten in doppelblinden Studien nachgewiesen worden sind. Vor dem Hintergrund der Einführung der DRG‐Richtlinien kann zudem die orale Verfügbarkeit von Linezolid und die damit verbundene kürzere Krankenhausverweildauer einen eigenen Vorteil darstellen.