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  • Chemistry  (993)
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  • 1
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 32 (1996), S. 55-63 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Titanium (Ti) surface roughness affects proliferation, differentiation, and matrix production of MG-63 osteoblast-like cells. Cytokines and growth factors produced in the milieu surrounding an implant may also be influenced by its surface, thereby modulating the healing process. This study examined the effect of surface roughness on the production of two factors known to have potent effects on bone, prostaglandin E2 (PGE2) and transforming growth factor β1 (TGF-β1). MG-63 cells were cultured on Ti disks of varying roughness. The surfaces were ranked from smoothest to roughest: electropolished (EP), pretreated with hydrofluoric acid-nitric acid (PT), fine sand-blasted, etched with HCl and H2SO4, and washed (EA), coarse sand-blasted, etched with HCl and H2SO4, and washed (CA), and Ti plasma-sprayed (TPS). Cells were cultured in 24-well polystyrene (plastic) dishes as controls and to determine when confluence was achieved. Media were collected and cell number determined 24 h postconfluence. PGE2 and TGF-β1 levels in the conditioned media were determined using commercial radioimmunoassay and enzyme-linked immunosorbent assay kits, respectively. There was an inverse relationship between cell number and Ti surface roughness. Total PGE2 content in the media of cultures grown on the three roughest surfaces (FA, CA, and TPS) was significantly increased 1.5-4.0 times over that found in media of cultures grown on plastic or smooth surfaces. When PGE2 production was expressed per cell number, CA and TPS cultures exhibited six- to eightfold increases compared to cultures on plastic and smooth surfaces. There was a direct relationship between TGF-β1 production and surface roughness, both in terms of total TGF-β1 per culture and when normalized for cell number. TGF-β1 production on rough surfaces (CA and TPS) was three to five times higher than on plastic. These studies indicate that substrate surface roughness affects cytokine and growth factor production by MG-63 cells, suggesting that surface roughness may modulate the activity of cells interacting with an implant, and thereby affect tissue healing and implant success. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 39 (1998), S. 77-85 
    ISSN: 0021-9304
    Schlagwort(e): implant ; titanium ; osteoblasts ; surface roughness ; 1α,25- (OH)2D3 ; differentiation ; local factor ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Surface roughness has been shown to affect differentiation and local factor production of MG63 osteoblast-like cells. This study examined whether surface roughness alters cellular response to circulating hormones such as 1α,25-(OH)2D3. Unalloyed titanium (Ti) disks were pretreated with HF/HNO3 (PT) and then were machined and acid-etched (MA). Ti disks also were sandblasted (SB), sandblasted and acid etched (CA), or plasma sprayed with Ti particles (PS). The surfaces, from smoothest to roughest, were: PT, MA, CA, SB, and PS. MG63 cells were cultured to confluence on standard tissue culture polystyrene (plastic) or the Ti surfaces and then treated for 24 h with either 10-8M or 10-7M 1α,25-(OH)2D3 or vehicle (control). Cellular response was measured by assaying cell number, cell layer alkaline phosphatase specific-activity, and the production of osteocalcin, latent (L) TGFβ, and PGE2. Alkaline phosphatase activity was affected by surface roughness; as the surface became rougher, the cells showed a significant increase in alkaline phosphatase activity. Addition of 1α,25-(OH)2D3 to the cultures caused a dose-dependent stimulation of alkaline phosphatase activity that was synergistic with the effect caused by surface roughness alone. 1α,25-(OH)2D3 also caused a synergistic increase in osteocalcin production as well as local factor (LTGFβ and PGE2) production on the rougher CA, SB, and PS surfaces, but it had no effect on the production on smooth surfaces. The inhibitory effect of surface roughness on cell number was not affected by 1α,25-(OH)2D3 except on the SB surface. 1α,25-(OH)2D3 decreased cell number, increased alkaline phosphatase activity and osteocalcin production, and had no effect on LTGFβ or PGE2 production by MG63 cells grown on tissue culture polystyrene. These data suggest that bone cell response to systemic hormones is modified by surface roughness and that surface roughness increases the responsiveness of MG63 cells to 1α,25-(OH)2D3. They also suggest that the endocrine system is actively involved in normal bone healing around implants. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 77-85, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 0021-9304
    Schlagwort(e): implant ; titanium ; osteoblasts ; prostaglandin ; indomethacin ; surface roughness ; 1α,25-(OH)2D3 ; differentiation ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Surface roughness affects proliferation, differentiation (alkaline phosphatase and osteocalcin), local factor production [transforming growth factor (TGFβ) and prostaglandin E2 (PGE2)], and response to 1,25-(OH)2D3 (1,25) of MG63 osteoblast-like cells. In this study, we examined whether the effect of surface roughness on MG63 cells is mediated by prostaglandins produced by the cells. Unalloyed titanium (Ti) disks were pretreated with HF/HNO3 (PT) and then machined and acid-etched (MA). Disks were also coarse grit-sandblasted (SB), coarse grit-sandblasted and acid-etched (CA), or plasma-sprayed with Ti particles (PS). The surfaces, from smoothest to roughest, were PT, MA, CA, SB, and PS. MG63 cells were cultured to confluence on the Ti disks in the presence or absence of 10-7M indomethacin (Indo), a specific inhibitor of cyclooxygenase activity, resulting in decreased prostaglandin production. When the cells reached confluence, cell number, cell layer alkaline phosphatase specific activity (ALPase), and osteocalcin (OC) and latent TGFβ (LTGFβ) production were determined. In addition, confluent cultures which had been grown in the absence of Indo were exposed to 10-7M 1,25, 10-7M Indo, or a combination of the two for 24 h. On the rougher surfaces, cell number was decreased and ALPase, OC, and LTGFβ were increased. When indomethacin was present throughout the culture period, the effect of surface roughness on cell number, OC, and LTGFβ was abolished. ALPase was reduced, but surface roughness-dependent effects were still observed. Addition of indomethacin to confluent cultures for 24 h had no effect on any of the parameters examined, with one exception: Cells cultured on MA surfaces exhibited a more differentiated phenotype. 1,25 increased all parameters examined on SB, CA, and PS surfaces. When indomethacin was added with 1,25, the 1,25-dependent effects on cell number and OC and LTGFβ production were abolished; however, ALPase was unaffected. This indicates that bone cell response to systemic hormones may be modified by implant surface roughness. This effect may be mediated, at least in part, by prostaglandins produced by the same cells. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 489-496, 1998.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: Although it is well accepted that implant success is dependent on various surface properties, little is known about the effect of surface roughness on cell metabolism or differentiation, or whether the effects vary with the maturational state of the cells interacting with the implant. In the current study, we examined the effect of titanium (Ti) surface roughness on chondrocyte proliferation, differentiation, and matrix synthesis using cells derived from known stages of endochondral development. Chondrocytes derived from the resting zone (RCs) and growth zone (GCs) of rat costochondral cartilage were cultured on Ti disks that were prepared as follows: HF-HNO3-treated and washed (PT); PT-treated and electropolished (EP); fine sand-blasted, HCl-H2SO4-etched, and washed (FA); coarse sand-blasted, HCl-H2SO4-etched, and washed (CA); or Ti plasma-sprayed (TPS). Based on surface analysis, the Ti surfaces were ranked from smoothest to roughest: EP, PT, FA, CA, and TPS. Cell proliferation was assessed by cell number and [3H]-thymidine incorporation, and RNA synthesis was assessed by [3H]-uridine incorporation. Differentiation was determined by alkaline phosphatase specific activity (AL-Pase). Matrix production was measured by [3H]-proline incorporation into collagenase-digestible (CDP) and noncollagenase-digestible (NCP) protein and by [35S]-sulfate incorporation into proteoglycan. GCs required two trypsinizations for complete removal from the culture disks; the number of cells released by the first trypsinization was generally decreased with increasing surface roughness while that released by the second trypsinization was increased. In RC cultures, cell number was similarly decreased on the rougher surfaces; only minimal numbers of RCs were released by a second trypsinization. [3H]-thymidine incorporation by RCs decreased with increasing surface roughness while that by GCs was increased. [3H]-Uridine incorporation by both GCs and RCs was greater on rough surfaces. Conversely, ALPase in the cell layer and isolated cells of both cell types was significantly decreased. GC CDP and NCP production was significantly decreased on rough surfaces while CDP production by RC cells was significantly decreased on smooth surfaces. [35S]-sulfate incorporation by RCs and GCs was decreased on all surfaces compared to tissue culture plastic. The results of this study indicate that surface roughness affects chondrocyte proliferation, differentiation, and matrix synthesis, and that this regulation is cell maturation dependent. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 175-190 
    ISSN: 0006-3592
    Schlagwort(e): protein-based polymers ; inverse temperature transitions ; hydrophobic-induced pKa shifts ; waters of hydrophobic hydration ; five axioms for protein engineering; microwave dielectric relaxation ; a universal mechanism for biological energy conversion ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Metabolism is the conversion of available energy sources to those energy forms required for sustaining and propagating living organisms; this is simply biological energy conversion. Proteins are the machines of metabolism; they are the engines of motility and the other machines that interconvert energy forms not involving motion. Accordingly, metabolic engineering becomes the use of natural protein-based machines for the good of society. In addition, metabolic engineering can utilize the principles, whereby proteins function, to design new protein-based machines to fulfill roles for society that proteins have never been called upon throughout evolution to fulfill.This article presents arguments for a universal mechanism whereby proteins perform their diverse energy conversions; it begins with background information, and then asserts a set of five axioms for protein folding, assembly, and function and for protein engineering. The key process is the hydrophobic folding and assembly transition exhibited by properly balanced amphiphilic protein sequences. The fundamental molecular process is the competition for hydration between hydrophobic and polar, e.g., charged, residues. This competition determines Tt, the onset temperature for the hydrophobic folding and assembly transition, Nhh, the numbers of waters of hydrophobic hydration, and the pKa of ionizable functions.Reported acid-base titrations and pH dependence of microwave dielectric relaxation data simultaneously demonstrate the interdependence of Tt, Nhh and the pKa using a series of microbially prepared protein-based poly(30mers) with one glutamic acid residue per 30mer and with an increasing number of more hydrophobic phenylalanine residues replacing valine residues. Also, reduction of nicotinamides and flavins is shown to lower Tt, i.e., to increase hydrophobicity.Furthermore, the argument is presented, and related to an extended Henderson-Hasselbalch equation, wherein reduction of nicotinamides represents an increase in hydrophobicity and resulting hydrophobic-induced pKa shifts become the basis for understanding a primary energy conversion (proton transport) process of mitochondria. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:175-190, 1998.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 587-594 
    ISSN: 0006-3592
    Schlagwort(e): biotransformation ; membrane bioreactor ; silicone rubber ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The Membrane Bioreactor for Biotransformations (MBB) is based on the aqueous/organic two-phase system, and uses a tubular silicone rubber membrane to separate the two liquid phases. This avoids the key problem associated with direct contact two-phase processes, specifically, product emulsification. The baker's yeast mediated reduction of geraniol to citronellol was used as a model biotransformation to demonstrate MBB operation. Values for the overall mass transfer coefficient were determined for geraniol, (2.0 × 10-5 ms-1), and for citronellol, (2.1 × 10-5 ms-1) diffusion across the silicone rubber membrane. Using these values, and the specific activity of the biocatalyst (5 nmols-1g biomass-1), a suitable membrane surface area: biomass ratio was determined as 2.4 × 10-3 m2g biomass-1. The bioreactor was operated at this surface area: biomass ratio and achieved a product accumulation rate 90-95% that of a conventional direct contact two-phase system. The slight reduction in product accumulation rate was shown not to be due to mass transfer limitations with respect to reactant delivery or product extraction. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 587-594, 1998.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 62 (1996), S. 1819-1833 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Multiblock copolymers offer the possibility to combine the properties of different polymers. Thus, new materials with tailor-made unique properties are available by coupling of different suitable polymeric segments. The goal of the work discussed in this paper was to combine advantageous properties of liquid-crystalline polymers (LCP) with those of polysulfone (PSU). Therefore, liquid crystalline poly(ethylene terephthalate-co-1,4-oxybenzoates) were connected with PSU oligomers. Chemically homogeneous multiblock copolymers with high molecular weight were obtained by a melt transesterification procedure. It was demonstrated by wide angle x-ray scattering (WAXS), polarizing microscopy, transmission electron microscopy (TEM), and differential scanning calorimetry (DSC) that the properties of the multiblock copolymers (solid phase structure, phase behavior, morphology, glass transition, and melting behavior) can be balanced by the segment length of the incorporated blocks. The investigations clearly reveal the existence of a two-phase structure. However, a change of properties compared to the corresponding homopolymers refers to certain interactions between the phase due to the chemical connection of the LCP and PSU segments. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    ISSN: 1075-4261
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Physik
    Notizen: Rapid advances in the generation of intense tunable ultrashort mid-infrared (IR) laser pulses allow the use of ultrafast IR pump-probe and vibrational echo experiments to investigate the dynamics of the fundamental vibrational transition of CO bound to the active site of heme proteins. The studies were performed using a free-electron laser (FEL) and an experimental set up at the Stanford University FEL Center. These novel techniques are discussed in some detail. Pump-probe experiments on myoglobin-CO (MbCO) measure CO vibrational relaxation (VR). The VR process involves loss of vibrational excitation from CO to the protein and solvent. Infrared vibrational echoes measure CO vibrational dephasing. The quantum mechanical treatment of the force-correlation function description of vibrational dynamics in condensed phases is described briefly. A quantum mechanical treatment is needed to explain the temperature dependence of VR in Mb-CO from 10 to 300 K. A molecular-level description including elements of heme protein structure in the treatment of vibrational dynamics is also discussed. Vibrational relaxation of CO in Mb occurs on the 10-11-s time scale. VR was studied in proteins with single-site mutations, proteins from different species, and model heme compounds. A roughly linear relationship between carbonyl stretching frequency and VR rate has been observed. The dominant VR pathway is shown to involve anharmonic coupling from CO through the π-bonded network of the porphyrin, to porphyrin vibrations with frequencies 〉 400 cm-1. The heme protein influences VR of bound ligands at the active site primarily via altering the through π-bond coupling between CO and heme. Preliminary vibrational echo studies of the effects of protein conformational relaxation dynamics on ligand dephasing are also reported. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 26 (1998), S. 461-470 
    ISSN: 0142-2421
    Schlagwort(e): W/TiN/Ti/Si contact structure ; MULSAM ; TEM ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The W/TiN/Ti/Si contact structures needed for ultra-large-scale integrated circuits have been studied using cross-sectional transmission electron microscopy (TEM) and multi-spectral Auger electron microscopy. Access to the Ti/Si interface for chemical characterization using SEM, Auger and electron energy-loss imaging and spectroscopy has been achieved by using a novel method of bevelled polishing of the silicon substrate material. Cross-sectional TEM was used to calibrate the depth scale in the MULSAM image sets, so allowing measurements of the thicknesses of various interfacial layers and the penetration of the ohmic contacts into the silicon. The TiN layer, providing adhesion of the tungsten as well as acting as a diffusion barrier, appears to have a domed shape, which penetrates the tungsten overlayer to a greater extent in the contact centres. The results of this work, combined with earlier, related, studies, enable a three-dimensional characterization of the bottom and sidewall structures in these contacts. © 1998 John Wiley & Sons, Ltd.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 24 (1996), S. 204-210 
    ISSN: 0142-2421
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Atomic force microscopy (AFM) shows that PTFE-on-silicon wafer tribological transfer films consist of narrow ribbons of PTFE, 〈1 μm wide and 〈10 nm high, aligned with the film draw direction. Within the ribbons the PTFE molecular chains are also aligned with the draw direction. Such materials are of interest as substrates for the epitaxial crystallization of polymers and small molecules. X-ray photoelectron spectroscopy demonstrates that the amount of PTFE put down increases with deposition temperature and pressure. The XPS azimuthal angle dependence at low electron take-off angle is consistent with the aligned ribbon morphology. Azimuthal and polar angle dependence and charging studies show that hydrocarbon contamination observed in the XPS spectrum is located on top of the silicon wafer substrate, in the channels between the PTFE ribbons. Imaging XPS confirms the pressure dependence of PTFE coverage, and at low deposition pressure reveals tracks of PTFE ∽100 μm wide, aligned with the film draw direction. Together with the AFM data this leads to a description of PTFE transfer films as fractal materials.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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