M Taborelli

University of Geneva, Genève, Geneva, Switzerland

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Publications (18)38.67 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Hydrogen desorption from argon plasma-treated titanium implants with a high surface roughness was studied. Implants with a high surface roughness have shown an increase in mechanical stability in bone tissue and a different behavior of osteoblasts in vitro. High surface roughness was produced by grit blasting and acid etching, resulting in an increase of the sub-surface hydrogen concentration and the formation of a titanium hydride. After an argon plasma treatment the surface oxide, which always covers titanum surfaces exposed to an oxygen-containing environment, and some of the hydrogen were sputtered away, decreasing the hydrogen concentration in the sub-surface region. Nuclear reaction analysis was used to determine the hydrogen concentration as a function of depth. The total amount of sub-surface (down to a depth of < or = 2 microm) hydrogen remaining after plasma treatment decreased with increasing plasma intensity to below the levels observed in non-acid-etched samples (approximately 1-2%). Thermal desorption spectroscopy was used for desorption studies and investigation of H(2) desorption activation energies. With a surface oxide present, the onset of hydrogen desorption is at ca 400 degrees C, which is the oxide decomposition temperature in vacuum, with an activation energy of ca 2 eV/molecule of H(2). After plasma treatment, that is, without surface oxide present, the onset of desorption was observed at ca 300 degrees C and with an activation energy of ca 0.8 eV/molecule of H(2), indicating a bulk diffusion-limited desorption.
    Journal of Biomedical Materials Research 01/2001; 54(1):20-9.
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    ABSTRACT: Changes in surface properties of titanium platelets exposed to a physiological solution (Hanks' solution) were studied by Auger electron spectroscopy and Attenuated Total Reflection Fourier Transform Infra Red spectroscopy for surface chemical composition analysis and by Scanning Force Microscopy for surface topography measurements. An adsorbed layer of calcium-phosphate was spontaneously formed on the titanium oxide surface and its thickness as well as the Ca/P ratio was found to increase with immersion time. After 71 days of immersion, the Ca/P ratio corresponded to that of brushite or monetite and after 6 months it was close to the value of hydroxyapatite. A higher Ca/P ratio was found for adsorption from solutions where the pH had been increased. After adsorption, the grains of the evaporated titanium substrate appeared slightly smoother because they were covered by a thin layer of calcium phosphate. A comparison between immersion in a Hanks' solution and solutions containing only phosphates or only calcium ions, showed that the presence of phosphates is necessary for the adsorption of Ca-ions.
    Applied Surface Science. 01/1999;
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    ABSTRACT: We present an investigation of the physico-chemical surface properties of commercially pure titanium coverslips which were submitted to various treatments designed to optimize their topography in view of application in oral implantology. The surface microroughness, chemical composition and water wettability were analyzed on titanium coverslips prepared by mechanical polishing, acid attack in HCl/H2SO4, after mechanical polishing or sandblasting, and titanium plasma-spray. The chemical composition has been measured by Auger electron spectroscopy. The treatments have no major influence on the surface chemical composition and all the samples display a composition approaching that of TiO2 with minor amounts of carbon, sulfur, silicon and calcium as impurities. The roughness has been measured by scanning force microscopy on an area of 20 microns x 20 microns on each sample. Polished titanium is smooth (peak-to-valley roughness 81 nm), whereas the acid-attacked surfaces exhibit a micro-roughness in the microns range (2100 nm for polished and acid attacked; 3600 nm for sandblasted and acid attacked) which is quite reproducible over large areas of the sample. The acid attacked samples present a subsurface layer which contains hydrogen below the native passivating oxide layer. Water wettability measurement shows that all surfaces are hydrophobic with a slightly higher contact angle for the acid attacked surfaces. The different treatments analyzed in this study essentially influence the surface roughness by preserving the chemical composition and the wettability properties of titanium native oxide surface layer.
    Clinical Oral Implants Research 07/1997; 8(3):208-16. · 3.43 Impact Factor
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    ABSTRACT: The influence of titanium surface properties on in vitro adsorption isotherms of fibronectin, promotion of Staphylococcus aureus adhesion, and binding of a monoclonal antibody to the cell-binding domain of fibronectin was examined. Treatments producing different surface roughness were applied to a single side of commercially pure titanium coverslips, which was either mechanically polished (P), or polished and then acid attacked with H2SO4/HCl (PA), or sandblasted and then acid attacked (SLA), whereas the untreated side was blocked by an albumin coating layer. Incubation of the coverslips with concentrations of soluble 3H-labelled fibronectin increasing from 1 to 16 micrograms/ml led to the saturation of all surfaces with immobilized protein from 4 to 16 micrograms/ml. Promotion of S. aureus adhesion by fibronectin adsorbed on all surfaces and binding of the monoclonal antibody to its cell-binding domain was to some extent proportional to the amount of immobilized protein but also showed some minor differences between surfaces. More important material-related differences were observed when fibronectin adsorption isotherms were expressed as a function of the effective, roughness-corrected surface area, yielding amounts of immobilized fibronectin on the rough PA and SLA titanium surfaces which were 50% lower than those adsorbed on either smooth P or polymethylmethacrylate coverslips used as controls. In conclusion, surface treatments increasing the surface roughness of titanium do not increase, but may partly decrease in vitro adsorption of fibronectin. Despite adsorbing different amounts of fibronectin, both rough and smooth titanium surfaces promote normal expression of 2 major functional domains of this protein.
    Clinical Oral Implants Research 07/1997; 8(3):217-25. · 3.43 Impact Factor
  • L Frauchiger, M Taborelli, P Descouts
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    ABSTRACT: Ti90Al6V4 alloy is used in orthopaedic medical implant applications because of its biocompatibility, corrosion resistance and mechanical load resistance. We characterized the time evolution of the surface composition of TiAlV, the surface roughness and the microstructure, which influence the formation of a suitable tissue-implant interface. For this we used Auger electron spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy and X-ray diffraction. The impurity diffusion was accelerated by annealing in ultra high vacuum. We found sulphur segregation from the bulk to the surface. The value of the activation energy of 150 kJ/mol allows us to conclude that diffusion at room temperature is too slow to influence the composition during the implant lifetime. The microstructure of the alloy is equiaxed at room temperature and is modified by annealing above 950°C with the appearance of a lamellar phase. In the diffractograms after the treatments performed in our study we always observed only the α-phase peaks. During annealing in air the surface oxide thickens and increases its vanadium content compared to the bulk alloy. This finding is relevant for high temperature applications, but also for the machining treatments on devices applied at room temperature since the possible surface heating during wear processes could modify the surface composition.
    Applied Surface Science 01/1997; 115(3):232-242. · 2.54 Impact Factor
  • M Taborelli, P Descouts
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    ABSTRACT: Scanning force (SFM) and scanning tunneling (STM) microscopies are suitable techniques for the investigation of the structure of organic monolayers. Results are presented on thioalkane monolayers and thiolipid monolayers on gold. Both molecules attach covalently to the gold surface. STM images of the self assembled dodecanethiol layer display the molecular order of the film and reveal the presence of defects at the molecular scale. Moreover, domains and domain boundaries can be distinguished. Thiolipid layers on gold have been observed by SFM. The monolayer separates in solid-analogous star shaped domains and fluid-analogous domains. Imaging under water demonstrates the stability of the layer.
    Analytical and Bioanalytical Chemistry 04/1996; 354(7-8):777-81. · 3.66 Impact Factor
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    ABSTRACT: Scanning force microscopy offers the possibility of observing protein molecules under liquid environment. The main difficulty in obtaining reproducible images is given by the low adhesion of the molecules to the substrate. Physisorbed molecules are displaced by the scanning tip or are resuspended in the medium. We have therefore performed a covalent immobilization of immunoglobulin G (IgG) or its monovalent Fab′ fragment on gold surfaces thanks to thiol groups. For this purpose, multiple thiol groups were chemically introduced into the IgG molecule by treatment with Traut’s reagent. As an alternative, for a Fab′ fragment, we prepared molecules with a single thiol group located close to the C terminus of the truncated heavy chain. Both immobilization techniques enable us to observe clearly discernable individual molecules in liquid media. The grafting of Fab′ fragments on gold surface open new opportunities to study protein interactions. © 1996 American Vacuum Society
    Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 04/1996; · 1.36 Impact Factor
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    ABSTRACT: Polyurethane and poly(vinyl pyrrolidone) (PVP)-coated polyurethane catheter surfaces were characterized by time of flight secondary ion mass spectrometry (TOF-SIMS) and were compared in terms of wettability and adhesion and friction properties by scanning force microscopy (SFM). Using TOF-SIMS, the presence of hard segments in the first layers of the polyurethane catheter were shown, and the presence of a PVP coating on the modified catheters was clearly identified. The PVP coating induced a hydrophilic surface after immersion of the catheters in water for several hours. When SFM experiments were carried out in water, the adhesive force developed between the PVP-coated surface and the tip became immeasurably small. Tribometric measurements along a 500-nm scan line quantified friction coefficients of 0.05 for the coated catheter and 0.50 for the native polyurethane catheter. The PVP coating on catheters provided smooth, soft, and nonadhesive surface properties, which would minimize difficulties during their insertion into the vessels of the patient. (C) 1996 John Wiley & Sons, Inc.
    Journal of Applied Polymer Science 01/1996; 61(11):1939-1948. · 1.40 Impact Factor
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    ABSTRACT: We investigated the adsorption of albumin on chemically modified gold surfaces by scanning force microscopy operating both in contact and noncontact mode. The surface modification was performed with thiol-based self-assembling molecules carrying amine or methyl groups. The albumin on the aminoethanethiol-coated gold formed a uniform layer and single molecules could be distinguished. On the dodecanethiol-coated surface the protein adsorbed in aggregates or single isolated molecules depending on the incubation time. The width of the albumin molecule on both surface was similar, but the height was much lower on the amine than on the methyl surface. This was interpreted as a difference in the conformation of albumin depending on the substrate, and could explain the promotion of cell adhesion on amine-treated polymers coated with albumin.
    Journal of Biomedical Materials Research 07/1995; 29(6):707-14.
  • M. Jobin, M. Taborelli, P. Descouts
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    ABSTRACT: Oxidized titanium surfaces resulting from various processes have been structurally characterized by means of scanning force microscopy, x‐ray photoemission spectroscopy (XPS), x‐ray diffraction, and electron energy‐loss spectroscopy (EELS) with losses in the 0–100 eV range. It has been found that the surface morphology has a granular structure for electropolished titanium and for titanium evaporated on mica at low substrate temperature (570 K), but changes to flat terraces for the films evaporated at higher temperature (770 K). Angular‐dependent XPS has revealed the presence of a Ti 2 O 3 suboxide at the Ti/TiO 2 interface for electropolished titanium. Dry oxidation has been performed at 770 and 970 K on both weakly and highly crystallized evaporated titanium films oriented along (0001). In the case of underlying crystallized metallic titanium, the resulting TiO 2 films are crystallized with the anatase (004) orientation for oxidation at 770 K and with rutile (200) orientation for oxidation at 970 K. EELS spectra interpreted in terms of the molecular orbitals of a (TiO 6 )<sup>8-</sup> cluster show that the local octahedral environment of titanium atoms is preserved on native oxides, even if these oxides are not crystallized. © 1995 American Institute of Physics.
    Journal of Applied Physics 06/1995; · 2.21 Impact Factor
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    ABSTRACT: Physisorbed and covalently bound Langmuir-Blodgett (LB) monolayers of sulfur-bearing lipids on mica and on gold substrates, resp., have been studied. Scanning force microscopy, in topog. and friction modes as well as in contact and non-contact modes have been used to investigate these films in the region of coexisting phases. For the first time, a detailed and complex internal structure of solid-analogous monolayer domains, reflecting their sym. morphol., has been obsd. Comparisons of physisorbed monolayers on mica with chemisorbed monolayers on gold show distinct differences in the structure and stability of the films caused by the different substrate/film interactions. If is found that the use of a substrate to which the film can bind covalently does not result in changes to the morphol. of solid-analogous domains in the films. The structure of covalently bound monolayers is well-preserved over long time periods and is stable at solid/fluid interfaces. However, the covalently bound LB monolayers are more susceptible to damage by the SFM tip than the physisorbed films on mica. [on SciFinder (R)]
    01/1995;
  • Source
    E Droz, M Taborelli, P Descouts, T N Wells
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    ABSTRACT: Scanning force microscopy has been used successfully to produce images of individual protein molecules. However, one of the problems with this approach has been the high mobility of the proteins caused by the interaction between the sample and the scanning tip. To stabilize the proteins we have modified the adsorption properties of immunoglobulin G on graphite and mica surfaces. We have used two approaches: first, we applied glow discharge treatment to the surface to increase the hydrophilicity, favoring adhesion of hydrophilic protein molecules; second, we used the arginine modifying reagent phenylglyoxal to increase the protein hydrophobicity and thus enhance its adherence to hydrophobic surfaces. We used scanning force microscopy to show that the glow discharge treatment favors a more homogeneous distribution and stronger adherence of the protein molecules to the graphite surface. Chemical modification of the immunoglobulin caused increased aggregation of the proteins on the surface but did not improve the adherence to graphite. On mica, clusters of modified immunoglobulins were also observed and their adsorption was reduced. These results underline the importance of the surface hydrophobicity and charge in controlling the distribution of proteins on the surface.
    Biophysical Journal 10/1994; 67(3):1316-23. · 3.67 Impact Factor
  • M. Jobin, M. Taborelli, P. Descouts
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    ABSTRACT: The surface topography, the chemical composition and the hydroxylation state are the surface properties playing a key role in the first stage of the biocompatibility process, namely the adsorption of water and proteins on the implant surface. To understand the very different tissue response to titanium and vanadium, we have measured the above-mentioned surface properties on similarly prepared Ti and V electropolished samples.Scanning force microscopy shows granular and homogeneous surfaces in both Ti and V samples, but with roughness twice as small in the case of V and with a lateral grain size of the order of 20–30 nm for Ti and of 80–100 nm for V. The surface chemical composition is strongly affected by thermal treatments, as revealed by Auger electron spectroscopy. On electropolished Ti, the surface segregation of Cl (originating from the electropolishing bath) occurs at 720 K and is well described by a purely diffusive model, i.e. Fick's law. For the segregation of S on Ti at higher temperature, we have extracted the energy of segregation and observed a rather strong influence of sulphur diffusion depending on the presence of chlorine on the surface. Finally, thermal desorption spectroscopy measurements indicate that water is mainly dissociated on hydroxyl groups on both Ti and V; the large amount of detected water indicates that it is deeply trapped inside the sample and not only chemisorbed on its surface.
    Applied Surface Science 12/1993; 72(4):363–372. · 2.54 Impact Factor
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    E Droz, M Taborelli, T N Wells, P Descouts
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    ABSTRACT: The T4 bacteriophage has been used to investigate protocols for the preparation of samples for scanning force microscopy in air, in order to obtaining reproducible images. The resolution of images and the distribution of bacteriophages on the substrate depends on the buffer type, its concentration, the surface treatment of substrate, and the method of deposition. The best imaging conditions for the phages require dilution in a volatile buffer at low ionic strength and adsorption onto hydrophilic surfaces. When imaging with the scanning force microscopy the quality of the images is influenced by the vertical and lateral forces applied on the sample and by the tip geometry.
    Biophysical Journal 10/1993; 65(3):1180-7. · 3.67 Impact Factor
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    ABSTRACT: We have imaged with scanning force microscopy in air fibronectin (Fn) molecules sprayed on mica and on polymethylmetacrylate (PMMA), the latter being extensively used as biomaterial for implants. On mica we can observe small aggregates as well as individual molecules whose shape is influenced by the tip interaction during the scanning process, most of the isolated molecules showing a V-shape oriented in the scan direction. This indicates that the arms of the molecules are relatively free to move and the binding to the mica substrate is located near the disulfide bridge between the two subunits of the molecule. On the other side, when Fn molecules are sprayed on PMMA under the same conditions as for mica, we observe a thin network which we interpret as Fn molecules bound to each other. We relate our observation to the fact that mica is known to be strongly hydrophilic, which could reduce the Fn binding properties by interacting relatively strongly with molecules. On the other side, PMMA being hydrophobic, would interact less with molecules, leaving more binding sites for inter-molecular attachment.
    Ultramicroscopy 08/1992; 42-44 ( Pt B):1155-60. · 2.47 Impact Factor
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    ABSTRACT: In this study, tobacco mosaic virus (TMV) provides a resolution criterion for specimen preparation methods as well as for imaging parameters of the scanning force microscope (SFM). We present scanning force microscopic images of the virus embedded in 0.5% buffered phosphotungstic acid solution adsorbed on a freshly cleaved mica surface, and imaged under atmospheric conditions. Individual TMV particles were clearly identified with a characteristic shape of long rods of about 300 nm long and 60-70 nm in apparent width due to the geometric parameters of the tip. The structure of the virus was compared with cryo-electron microscopic data of vitrified suspensions observed to a resolution of 1.15 nm. Uncoated TMV particles were also deposited on evaporated titanium thin films and imaged by SFM.
    Ultramicroscopy 08/1992; 42-44 ( Pt B):1168-72. · 2.47 Impact Factor
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    ABSTRACT: The scanning probe microscopies applied to the sequencing of DNA is a challenging goal attempted by several groups. But one limitant parameter has been the sample preparation of DNA molecules. Here we report how to hold DNA molecules fixed on mica substrate and we show the three-dimensional configuration of double-stranded DNA obtained with our scanning force microscope. We can image DNA under negative supercoiling, a feature of general importance controlling the activities of DNA. We compared the electron micrographs of a carbon replica of the same DNA specimen with scanning force images which demonstrates well the feasibility and accuracy of our scanning probe measurements.
    Journal of Structural Biology 01/1992; 108(1):69-73. · 3.36 Impact Factor
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    ABSTRACT: Surface properties and dissociative chemisorption of water on titanium-oxide surfaces are of particular interest for the biocompatibility of this material. Scanning force microscopy images of electropolished titanium samples and of thin films of titanium evaporated under vacuum show a similar topography with a grain size of 30 nm. Mass spectrometer thermal desorption spectroscopy displays two peaks for e/m = 18, at 380 and 520 K corresponding to adsorbed water molecules and hydroxyl groups, respectively. Auger spectra show the segregation toward the surface of chlorine from the metal-oxide interface upon heating at 720 K and of sulphur from the bulk after annealing at 950 K. The oxygen diffusion from the surface toward the bulk during the heating process induces a metallic behaviour of the surface layer which is revealed by tunneling spectroscopy: the semiconducting gap present in dI/dV curves for the air-exposed sample vanishes upon annealing. STM images of the annealed surface show the presence of tiny crystallites of a few nm in size.
    Ultramicroscopy s 42–44:637–643. · 2.47 Impact Factor

Publication Stats

211 Citations
38.67 Total Impact Points

Institutions

  • 1992–2001
    • University of Geneva
      • Department of Applied Physics
      Genève, Geneva, Switzerland