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  • 1.
    Hakobyan, Shoghik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Barbero, David R.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Functionalization of zwitterionic polymer brushes, do they remain antifouling?2018In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 50, no 11, p. 1001-1006Article in journal (Refereed)
    Abstract [en]

    Polymer brushes are surface coatings that can be tailored in many ways to suit specific demands including reduction of protein and bacterial fouling of biomaterials. Previously, we reported that antifouling poly (2-(methacryloxy)ethyl)dimethyl-3-sulphopropyl ammonium hydroxide) brushes dramatically reduced formation of bacterial biofilm. We hypothesized that: (1) this brush could be efficiently functionalized with a small molecule (2-oxo-2-[N-(2,4,6-trihydroxybenzylidene)-hydrazino]-acetamide, ME0163, hydrazone) and that (2) the antifouling property would remain also after functionalization. Diblock co-polymer brushes of 2-(methacryloxy)ethyl)dimethyl-3-sulphopropyl ammonium hydroxide and poly (glycidyl methacrylate) were formed by surface-initiated atom transfer radical polymerization (SI-ATRP), and the ME0163 hydrazone was covalently bound to the surface via a ring-opening reaction. Functionalization of the surfaces was followed by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and UV-Vis spectroscopy. The influence of temperature, reaction time, and reagent concentrations on the immobilization process was investigated. Surfaces with high degree of functionalization could be made in this way. However, the functionalization rendered the surface more hydrophobic, and the antifouling property of the brush was lost, thus, disproving the second of our starting hypotheses but corroborating the first.

  • 2.
    Mladenovic, Zivko
    et al.
    Umeå University, Faculty of Medicine, Department of Odontology.
    Sahlin-Platt, Annika
    Umeå University, Faculty of Medicine, Department of Odontology.
    Bengtsson, Åsa
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ransjö, Maria
    Umeå University, Faculty of Medicine, Department of Odontology.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Surface characterization of bone graft substitute materials conditioned in cell culture medium2010In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 42, no 6-7, p. 452-456Article in journal (Refereed)
    Abstract [en]

    Biomaterials are widely used in clinical practice as bone graft substitutes for treating patients with bone defects. A molecular level understanding of the chemical processes at the interface between the biomaterial and the biological environment is crucial to succeed in tissue regeneration and to predict the treatment outcome. In this study, we used three different bone graft substitute materials (BioGlass 45S5—synthetic, Bio-Oss—bovine derived and Algipore—derived from algae) which were incubated in an α-minimum essential medium (α-MEM) during 1, 3 and 7 days. Initial surface composition of the biomaterials and the chemistry of their solid–solution interface were monitored by XPS with a fast-frozen samples technique. The XPS analysis showed that the equilibrium at the solid-solution interface is reached within 24 h. The Na/Cl atomic ratio at equilibrium indicates a negatively charged surface for Bio-Oss. In contrast, the other two materials gained a positive surface charge, which resulted in pronounced adsorption of amino acids at the interface from the medium. The surface chemical reconstruction and charge generation mechanism responsible for this effect are discussed with regard to bulk composition of the materials and possible proliferation and differentiation cell patterns that could be expected at the interface. Copyright © 2010 John Wiley & Sons, Ltd.

  • 3.
    Ramstedt, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Franklyn, Paul
    Difficulties in determining valence for Ag0 nanoparticles using XPS—characterization of nanoparticles inside poly (3-sulphopropyl methacrylate) brushes2010In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 42, no 6-7, p. 855-858Article in journal (Refereed)
    Abstract [en]

    The formation of silver nanoparticles (10–20 nm) inside poly (3-sulfopropyl methacrylate) brushes was studied by using transmission electron microscopy, UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS). Initially, the silver forms Ag clusters that are stabilised by the anionic side groups of the brush. In the presence of a reducing agent, these clusters aggregate into nanoparticles or films. The apparent oxidation state for silver in the different forms was examined using XPS and a chemical state plot. It was seen that the nanoparticles do not display the same chemical shift as the silver film does. The reason for this observation is suggested to be the final and initial state effects. The latter is related to the relatively high amount of under coordinated or charged surface atoms on these particles.

  • 4.
    Shchukarev, Andrey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Boily, Jean-François
    XPS study of the hematite-aqueous solution interface2008In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Surface and Interface Analysis, Vol. 40, no 3-4, p. 349-353Article in journal (Refereed)
    Abstract [en]

    The interaction between the surface of hematite colloidal platelets and Na+ and Cl- ions was investigated by XPS using the cryogenic technique. Pastes in ionic strengths of 0 and 10 mM NaCl contained about 10 at. % water and water/NaCl atomic ratios of 3 to 6. These results fall within the range of values obtained for a variety of minerals studied with this technique. Pastes in 100 mM NaCl background electrolyte, however, contained an unusually larger water content of 25 at. %, yielding a Na+: Cl-: H2O ratio of 1:1:2. This result is in strong contrast with other minerals at the same ionic strength, which typically reveal about 10 at. % water. Substituting Na+ for Cs+ in the hematite paste with 100 mM CsCl yielded, on the other hand, the same amount of water as in the pastes with 0 and 10 mM NaCl, and underpinned the role of Na+ ions in the large water content of the hematite paste. As surface concentrations of Na+ and Cl- exceeded those of hematite surface structural hydroxyl groups and Na 1s and Cl 2p spectra exhibited energy loss features, the electrolyte ions are proposed to be distributed in a three-dimensional array in the fast-frozen paste, possibly in a hydrohalite-like (NaCl·2H2O) phase. In addition, because the fast-frozen solution of 100 mM NaCl yields a water/NaCl ratio of about 70, hematite is proposed to play an important role in the stabilization of this three-dimensional distribution of Na+ and Cl- ions. The role of the neutrally charged {001} plane, a predominant feature in the hematite particles of this study, is notably discussed in the light of recent molecular models showing that this plane can stabilize several layers of hydrated ions up to 15 Å from the surface.

  • 5.
    Shchukarev, Andrey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gälman, Veronika
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Rydberg, Johan
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Renberg, Ingemar
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Speciation of iron and sulphur in seasonal layers of varved lake sediment: an XPS study2008In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 40, no 3-4, p. 354-357Article in journal (Refereed)
    Abstract [en]

    Under specific conditions, annually-laminated (varved) sediments are formed in lakes. Such lake sediments are rare, but of great interest to studies of past environmental conditions since they provide annual or even seasonal time resolution, and can be used to follow environmental changes over hundreds or thousands of years. The chemical composition of the varves and speciation of chemical elements reveal information on past conditions. The colour of sediment varves can vary between light brown to almost black, and it was hypothesised that black layers were deposited in seasons with oxygen deficit in the hypolimnion (summer and winter) and light layers were formed at spring and autumn over-turn periods when oxygen-rich water flow occurred near the lake bottom. We have tested this hypothesis by analyses of seasonal layers of varves formed in 1968 and 2005 using X-ray photoelectron spectroscopy with fast-frozen samples. We found that the organic (C, N, O, S) and inorganic (Al, Si, Ca, Fe, S) elemental composition was similar for all samples studied, but the chemical states of iron and sulphur differed remarkably depending on the season. The black colour of the summer layer was caused by the precipitation of inorganic FeS, while in the light layers only organic thiol (SH) and sulphate SO42- together with Fe(III) hydroxides were found.

  • 6.
    Shchukarev, Andrey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mladenovic, Zivko
    Umeå University, Faculty of Medicine, Department of Odontology, Ortodontics.
    Ransjö, Maria
    Umeå University, Faculty of Medicine, Department of Odontology, Ortodontics.
    Surface characterization of bone graft substitute materials conditioned in cell culture medium. 2. Protein adsorption2012In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 44, no 8, p. 919-923Article in journal (Refereed)
    Abstract [en]

    Three bone graft substitute materials (Bioglass 45S5, Bio-Oss (R) and Algipore (R)) were conditioned in a-minimum essential medium (alpha-MEM), with the addition of 10% fetal bovine serum (FBS), for 1 and 7?days. The chemistry of their solid-solution interface was monitored by X-ray photoelectron spectroscopy, using fast-frozen sample technique, and compared to that reported for original alpha-MEM. FBS added to the biological medium causes significant changes in the interface after only 1day of conditioning. Interfacial chemical composition and N 1s spectra show immediate adsorption of proteins at the surface of all three biomaterials, independent of their surface charge and chemical composition. However, the atomic ratio C/N and the C 1s spectra indicate a different orientation of adsorbed serum proteins, which is dependent on the particle's surface charge. Moreover, the adsorption of serum proteins at the surface of Bio-Oss causes a charge reversal at the interface, as evidenced by the change in the atomic ratio of Na/Cl. In addition to the particle's surface charge, the formation of the protein interfacial layer at the surface of the biomaterial seems to be the second major phenomenon important for subsequent cell recognition and the initiation of biomineralization. Copyright (c) 2012 John Wiley & Sons, Ltd.

  • 7.
    Shchukarev, Andrey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Cryo-XPS: probing intact interfaces in nature and life2017In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 49, no 4, p. 349-356Article in journal (Refereed)
    Abstract [en]

    Experimental studies of solid–aqueous solution interfaces are of great importance for reaching a better chemical understanding ofinterfacial phenomena at the molecular level. This perspective article presents a recently developed approach for investigation ofintact interfaces, based on fast freezing of centrifuged wet pastes followed by traditional XPS measurements at liquid nitrogentemperatures. Sample preparation and handling protocols, applicable to any suspension or gel, are discussed in detail. For mineralsuspensions, cryogenic XPS is an important complement to traditional analyses of supernatant solutions and dry solids that iscapable of revealing novel insights of the electrical double layer in terms of structure and composition. It can be used to studychanges in the biochemistry of bacterial cell walls as influenced by external stimuli, and interfacial features related tobiocompatibility of implant materials. Herein we review how the technique has been applied to minerals in electrolyte solutions,intact bacterial surfaces, and biomaterial interfaces in biologically relevant media, and highlight some future requirements fordevelopment of interface analysis methodologies.

1 - 7 of 7
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