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  • 1
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The formation of an extracellular matrix (ECM) was investigated by the secretion of cellular FN during 72 h incubation of fibroblasts on defined hydrophilic glass and hydrophobic octadecyl glass (ODS). It was found, that the ability of fibroblasts to form their own ECM was inhibited on the hydrophobic ODS in comparison to glass, where significant amounts of FN were deposited in fibrils and clusters. This result was corroborated by the impaired morphology of cells on ODS, visualized by staining of actin micro-filaments and the FN receptor. Moreover, it was found that cell growth was significantly inhibited on the hydrophobic surface. In contrast to these findings, cell morphology and proliferation was not impaired on glass. Precoating of both substrata with FN could restore the cell morphology and enhanced the proliferation on the hydrophobic ODS. ELISA for FN binding using polyclonal and monoclonal antibodies revealed that under these circumstances total FN adsorption, as well as the presence of cell- and heparin-binding domains was much higher on ODS in comparison to glass.
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  • 2
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Several medical applications may benefit from biodegradable hemocompatible materials. Therefore a commercial biodegradable polylactide (RESOMER® R208; Boehringer-Ingelheim, Germany) was modified with heparin. The immobilization of heparin was performed by covalent binding with glutaraldehyde as spacer. Reaction conditions were varied to optimize the coupling of heparin. The efficiency of the immobilization and the biological activity of bonded heparin was estimated with a toluidine blue assay and factor Xa assay, respectively. It was shown that an immobilization at ambient temperature and a reaction time of 2 h yielded maximal heparin binding and biological activity. The hemocompatibility of the modified polylactide was tested after blood/material contact with an enzyme immuno assay (EIA) for GMP 140, a marker of platelet activation. The investigated materials were compared with polypropylene and Pellethane®. After modification it was found that high heparin binding and biological activity were correlated with very small activation of platelets.
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  • 3
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: It is a general trend that mammalian cells interact better with wettable surfaces than with non-wettable surfaces. The basis for this difference is still poorly understood. In this study hydrophilic clean glass and hydrophobic octadecyl glass have been used as model surfaces. We show that fibroblasts on hydrophilic surfaces may reorganize fluorescent fibronectin (FN) in an extracellular matrix-like structure whereas on hydrophobic surfaces no rearrangement of FN occurs. This was accompanied by a high proliferation of fibroblasts on clean glass whereas on octadecyl glass no cell growth occurred. Moreover, it was demonstrated that there are striking differences in the morphology of fibroblasts adhering to hydrophilic and hydrophobic surfaces, judged by the overall cell shape, the organization of FN receptors and actin filaments. Indeed, the preadsorption of FN on these surfaces could almost abolish morphological differences between hydrophilic and hydrophobic surfaces. However, preadsorption of FN could not restore the proliferation of fibroblasts on the hydrophobic surface. Taken together, the results suggest that the method of adsorption and reorganization of FN may be critical for the biocompatibility of materials.
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  • 4
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Biodegradable poly-(D,L-lactide) RESOMER® R208 and poly(D,L-lactide-co-glycolide) RESOMER® RG756 were heparinized to improve the blood contacting properties of the materials. The immobilization of heparin was performed with glutaraldehyde as coupling agent. The efficacy of the surface modification was monitored with respect to the total amount of bound heparin measured by a toluidine blue assay, the anticoagulant potential estimated by a factor Xa assay, and the activation of platelets estimated by a GMP140 assay. It was found that a reaction at ambient temperature for 2h resulted in optimal heparin binding, with high anticoagulant activity and low thrombogenicity. The storage of heparinized polylactide in saline solutions up to 8 days demonstrated the release of small quantities of heparin into the fluid. A further finding was that with prolonged storage the anticoagulant potential was improved, whereas the thrombogenicity decreased. Comparison of platelet activation on RESOMER® R208 as unmodified and heparinized material with polypropylene and Pellethane® revealed that heparinization of R208 substantially improved the haemocompatibility. Coating and subsequent heparinization of intravascular stents were carried out with RESOMER® RG756 because of its more appropriate mechanical properties.In vitro studies with blood under flow conditions demonstrated that platelet activation on Palmaz™ stents was considerably diminished after polymer coating and heparinization.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 548 (1987), S. 76-88 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation and Spectroscopic Characterization of Fluoro-Chloro-Iridates(V)By careful oxidation of the pure fluoro-chloro iridates(IV) with BrF3 in dichloromethane the corresponding pentavalent complexes [IrF5Cl]-, cis-[IrF4Cl2]-, and fac-[IrF3Cl3]- are formed without replacements of Cl ligands. The vibrational spectra of these mixed ligand complexes are assigned according to point groups C4v, C2v, and C3v. The increased bond strength compared with the corresponding IrIV compounds is indicated by a significant shift to higher energy by about 5-15%. The anomalous intensities of some of the Raman active fundamentals are attributed to the resonance Raman effect. The electronic absorption spectra are measured on the solid tetraethylammonium salts of the fluoro-chloro iridates(V) at 10 K. The strong bands in the UV/VIS region are assigned to charge transfer transitions from π(t1u, t2u) and σ(t1u) Cl orbitals into the π(t2g4)IrV level. The intraconfigurational transitions within the t2g4 configuration of IrV are split by spin orbit coupling and lowered symmetry, observed in the ranges 3000, 5100-6400, 10900-13000, and 18200 cm-1. The O—O transitions are deduced from the vibrational fine structure; in some cases they are confirmed by electronic Raman bands. With increasing number of F ligands all absorption bands are shifted systematically to higher energies.
    Notes: Bei der vorsichtigen Oxydation der reinen Fluoro-Chloro-Iridate(IV) mit BrF3 in Dichlormethan entstehen ohne Austausch von Cl-Liganden die entsprechenden fünfwertigen Komplexe [IrF5Cl]-, cis-[IrF4Cl2]- und fac-[IrF3Cl3]-. Die Schwingungsspektren dieser Gemischtligandkomplexe werden entsprechend den Punktgruppen C4v, C2v und C3v zugeordnet. Die größere Bindungsfestigkeit im Vergleich mit den entsprechenden IrIV-Verbindungen zeigt sich in einer deutlichen Verschiebung der Banden zu höherer Energie um etwa 5-15%. Die anomalen Intensitäten einiger Ra-aktiver Grundschwingungen lassen sich auf den Resonanz-Raman-Effekt zurückführen. Die elektronischen Absorptionsspektren werden an den festen Tetraethylammoniumsalzen der Fluoro-Chloro-Iridate(V) bei 10 K gemessen. Die intensiven Banden im UV/VIS-Spektralbereich werden Charge-Transfer-Übergängen aus π(t1u, t2u) und σ(t1u) Orbitalen an Cl-Liganden in das π(t2g4)IrV-Niveau zugeordnet. Die Intrakonfigurationsübergänge innerhalb der t2g4-Konfiguration von IrV sind durch Spin-Bahn-Kopplung und Symmetrieerniedrigung aufgespalten, man beobachtet sie in den Bereichen 3000, 5100-6400, 10900-13000 und 18 200 cm-1. Die O—O-Übergänge ergeben sich aus der Analyse der Schwingungsfeinstruktur; in einigen Fällen werden sie durch elektronische Raman-Banden bestätigt. Mit zunehmender Anzahl der F-Liganden verschieben sich alle Absorptionsbanden systematisch zu höheren Energien.
    Additional Material: 4 Ill.
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