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  • 1.
    Barbero, David
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Boulanger, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Yu, Junchun
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Carbon nanotube networks: nano-engineering of SWNT networks for enhanced charge transport at ultralow nanotube loading2014In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 26, no 19, p. 3164-Article in journal (Refereed)
    Abstract [en]

    Arrays of nano-engineered carbon nanotube networks embedded in nanoscale polymer structures enable highly efficient charge transport as demonstrated by D. R. Barbero and co-workers on page 3111. An increase in charge transport by several orders of magnitude is recorded at low nanotube loading compared to traditional random networks in either insulating (polystyrene) or semiconducting (polythiophene) polymers. These novel networks are expected to enhance the performance of next generation hybrid and carbon based photovoltaic devices.

  • 2.
    Barbero, David
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Boulanger, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Yu, Junchun
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nano-engineering of SWNT networks for enhanced charge transport at ultralow nanotube loading2014In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 26, no 19, p. 3111-3117Article in journal (Refereed)
    Abstract [en]

    We demonstrate a simple and controllable method to form periodic arrays of highly conductive nano-engineered single wall carbon nanotube networks from solution. These networks increase the conductivity of a polymer composite by as much as eight orders of magnitude compared to a traditional random network. These nano-engineered networks are demonstrated in both polystyrene and polythiophene polymers.

  • 3.
    Barzegar, Hamid R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nitze, Florian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sharifi, Tiva
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Tai, Cheuk W.
    Malolepszy, Artur
    Stobinski, Leszek
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Simple Dip-Coating Process for the Synthesis of Small Diameter Single-Walled Carbon Nanotubes-Effect of Catalyst Composition and Catalyst Particle Size on Chirality and Diameter2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 22, p. 12232-12239Article in journal (Refereed)
    Abstract [en]

    We report on a dip-coating method to prepare catalyst particles (mixture of iron and cobalt) with a controlled diameter distribution on silicon wafer substrates by changing the solution's concentration and withdrawal velocity. The size and distribution of the prepared catalyst particles were analyzed by atomic force microscopy. Carbon nanotubes were grown by chemical vapor deposition on the substrates with the prepared catalyst particles. By decreasing the catalyst particle size to below 10 nm, the growth of carbon nanotubes can be tuned from few-walled carbon nanotubes, with homogeneous diameter, to highly pure single-walled carbon nanotubes. Analysis of the Raman radial breathing modes, using three different Raman excitation wavelengths (488, 633, and 785 nm), showed a relatively broad diameter distribution (0.8-1.4 nm) of single-walled carbon nanotubes with different chiralities. However, by changing the composition of the catalyst particles while maintaining the growth parameters, the chiralities of single-walled carbon nanotubes were reduced to mainly four different types, (12, 1), (12, 0), (8, 5), and (7, 5), accounting for about 70% of all nanotubes.

  • 4. Bielig, H
    et al.
    Rompikuntal, Pramod Kumar
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Mitesh, Dongre
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Zurek, B
    Lindmark, B
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wai, Sun Nyunt
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Kufer, T A
    University of Cologne.
    NOD-like receptor activation by outer-membrane vesicles (OMVs) from non-O1 non-O139 Vibrio cholerae is modulated by the quorum sensing regulator HapR2011In: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 79, no 4, p. 1418-1427Article in journal (Refereed)
    Abstract [en]

    Vibrio cholerae is an inhabitant of aquatic systems and one of the causative agents of severe dehydrating diarrhea in humans. It has also emerged as an important cause of different kinds of inflammatory responses and in particular, V. cholerae strains of the non-O1 non-O139 serogroups (NOVC) have been associated with such infections in human. We analyzed the potential of outer membrane vesicles (OMVs) derived from the NOVC strain V:5/04 to induce inflammatory responses in human host cells. V:5/04 OMVs were taken up by human epithelial cells and induced inflammatory responses. siRNA-mediated gene knock-down revealed that the inflammatory potential of NOVC OMVs was partially mediated by the nucleotide-binding domain, leucine rich repeat containing family member NOD1. Physiochemical analysis of the content of these OMVs, in conjunction with NOD1 and NOD2 reporter assays in HEK293T cells, confirmed the presence of both NOD1 and NOD2 active peptidoglycan in the OMVs. Furthermore, we show that deletion of the quorum sensing regulator HapR which mimics an infective life style, specifically reduced the inflammatory potential of the V:5/04 OMVs and their ability to activate NOD1 and NOD2. In conclusion, our study shows that NOVC OMVs elicit immune responses mediated by NOD1 and NOD2 in mammalian host cells. Moreover, we provide evidence that the quorum sensing machinery plays an important regulatory role in this process by attenuating the inflammatory potential of OMVs in infective conditions. This work thus identified a new facet of how Vibrio affects host immune responses and defines a role for the quorum sensing machinery in this process.

  • 5. Bjarnsholt, T.
    et al.
    Buhlin, K.
    Dufrêne, Y. F.
    Gomelsky, M.
    Moroni, A.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Rumbaugh, K. P.
    Schulte, T.
    Sun, L.
    Åkerlund, B.
    Römling, U.
    Biofilm formation – what we can learn from recent developments2018In: Journal of Internal Medicine, ISSN 0954-6820, E-ISSN 1365-2796, Vol. 284, no 4, p. 332-345Article in journal (Refereed)
    Abstract [en]

    Although biofilms have been observed early in the history of microbial research, their impact has only recently been fully recognized. Biofilm infections, which contribute to up to 80% of human microbial infections, are associated with common human disorders, such as diabetes mellitus and poor dental hygiene, but also with medical implants. The associated chronic infections such as wound infections, dental caries and periodontitis significantly enhance morbidity, affect quality of life and can aid development of follow-up diseases such as cancer. Biofilm infections remain challenging to treat and antibiotic monotherapy is often insufficient, although some rediscovered traditional compounds have shown surprising efficiency. Innovative anti-biofilm strategies include application of anti-biofilm small molecules, intrinsic or external stimulation of production of reactive molecules, utilization of materials with antimicrobial properties and dispersion of biofilms by digestion of the extracellular matrix, also in combination with physical biofilm breakdown. Although basic principles of biofilm formation have been deciphered, the molecular understanding of the formation and structural organization of various types of biofilms has just begun to emerge. Basic studies of biofilm physiology have also resulted in an unexpected discovery of cyclic dinucleotide second messengers that are involved in interkingdom crosstalk via specific mammalian receptors. These findings even open up new venues for exploring novel anti-biofilm strategies.

  • 6. Chung, Jade C. S.
    et al.
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Welch, Martin
    Type III secretion system expression in oxygen-limited Pseudomonas aeruginosa cultures is stimulated by isocitrate lyase activity2013In: Open Biology, ISSN 2046-2441, E-ISSN 2046-2441, Vol. 3, article id 120131Article in journal (Refereed)
    Abstract [en]

    Pseudomonas aeruginosa is an opportunistic human pathogen and a common cause of chronic infections in individuals with cystic fibrosis (CF). Oxygen limitation was recently reported to regulate the expression of a major virulence determinant in P. aeruginosa, the type III secretion system (T3SS). Here, we show that expression of the T3SS in oxygen-limited growth conditions is strongly dependent on the glyoxylate shunt enzyme, isocitrate lyase (ICL; encoded by aceA), which was previously shown to be highly expressed in CF isolates. ICL-dependent regulation of the T3SS did not alter the expression level of the master transcriptional regulator, ExsA, but did affect expression of the T3 structural proteins, effectors and regulators (ExsC, ExsD and ExsE). An aceA mutant displayed enhanced biofilm formation during anaerobic growth, which suggested that AceA-dependent modulation of type III secretion might impinge upon the RetS/LadS signalling pathways. Indeed, our data suggest that RetS is able to mediate some of its effects through AceA, as expression of aceA in trans partially restored T3SS expression in a retS mutant. Our findings indicate that AceA is a key player in the metabolic regulation of T3SS expression during oxygen-limited growth of P. aeruginosa. To the best of our knowledge, this is the first demonstration that the T3SS can be regulated by factors that do not affect ExsA expression levels.

  • 7. Dias, Roberta P.
    et al.
    da Hora, Gabriel C. A.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Soares, Thereza A.
    Outer Membrane Remodeling: The Structural Dynamics and Electrostatics of Rough Lipopolysaccharide Chemotypes2014In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 10, no 6, p. 2488-2497Article in journal (Refereed)
    Abstract [en]

    Lipopolysaccharides (LPS) are the primary constituent of the outer membrane of Gram-negative bacteria such as Pseudomonas aeruginosa. Gram-negative bacteria can synthesize modified forms of LPS in response to environmental stimuli or due to genetic mutations, a process known as outer membrane remodeling. Chemical modifications of the LPS modulate the integrity and antibiotic susceptibility of bacterial outer membranes. It also governs microbial adhesion to tissues and artificial material surfaces. We have extended a previous model of the rough LPS to include four novel chemotypes rmlC, galU, LPS Re, and Lipid-A. Atomistic molecular dynamics (MD) simulations were performed for outer membrane models constituted of each LPS chemotypes and 1,2-dipalmitoyl-3-phosphatidylethanolamine. It is shown that the decrease in the LPS polysaccharide chain length leads to a significant increase in the diffusion coefficients for the Ca2+ counterions, increase in acyl chain packing (decrease in membrane fluidity), and attenuation of the negative potential across the LPS surface as positive counterions becomes more exposed to the solvent. The electrostatic potential on the LPS surfaces reflects heterogeneous charge distributions with increasingly larger patches of positive and negative potentials as the polysaccharide chain length decreases. Such a pattern originates from the spatial arrangement of charged phosphate-Ca2+ clusters in the LPS inner-core that becomes exposed in the membrane surface as monosaccharide units are lost in the shortest chemotypes LPS Re and Lipid-A. These MD-derived conformational ensembles reproduce experimental trends and provide atom-level structural information on the rough LPS chemotypes that can help to rationalize antibiotic resistance and bacterial adhesion processes.

  • 8. Ferreira, Magda
    et al.
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Grenho, Liliana
    Malheiros, Danila
    Gonçalves, Lídia
    Almeida, António J.
    Jordão, Luisa
    Ribeiro, Isabel A.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gomes, Pedro
    Bettencourt, Ana
    Levofloxacin-loaded bone cement delivery system: highly effective against intracellular bacteria and Staphylococcus aureus biofilms2017In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 532, no 1, p. 241-248Article in journal (Refereed)
    Abstract [en]

    Staphylococcus aureus is a major pathogen in bone associated infections due to its ability to adhere and form biofilms on bone and/or implants. Moreover, recrudescent and chronic infections have been associated with S. aureus capacity to invade and persist within osteoblast cells. With the growing need of novel therapeutic tools, this research aimed to evaluate some important key biological properties of a novel carrier system composed of acrylic bone cement (polymethylmethacrylate – PMMA), loaded with a release modulator (lactose) and an antibiotic (levofloxacin).

    Levofloxacin-loaded bone cement (BC) exhibited antimicrobial effects against planktonic and biofilm forms of S. aureus (evaluated by a flow chamber system). Moreover, novel BC formulation showed high anti-bacterial intraosteoblast activity. This fact led to the conclusion that levofloxacin released from BC matrices could penetrate the cell membrane of osteoblasts and be active against S. aureus strains in the intracellular environment. Furthermore, levofloxacin-BC formulations showed no significant in vitro cytotoxicity and no allergic potential (measured by the in vivo chorioallantoic membrane assay). Our results indicate that levofloxacin-loaded BC has potential as a local antibiotic delivery system for treating S. aureus associated bone infections.

  • 9. Gautrot, Julien E
    et al.
    Huck, Wilhelm T S
    Welch, Martin
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Chemistry.
    Protein-Resistant NTA-Functionalized Polymer Brushes for Selective and Stable Immobilization of Histidine-Tagged Proteins2010In: Applied Materials & Interfaces, Vol. 2, no 1, p. 193-202Article in journal (Refereed)
    Abstract [en]

    Protein-resistant polymeric coatings that allow highly selective immobilization of specific biomolecules are essential for biomedical applications such as microarrays, biosensing, heterogeneous catalysis, and bioengineering. Polymer brushes are particularly interesting for this purpose because their chemical structure and physical properties can easily be tailored to meet specific needs. This article explores the functionalization of two protein-resistant polymer brushes, poly(oligoethylene glycol methacrylate) (POEGMA) and poly(hydroxyethyl methacrylate) (PHEMA), with nitrilotriacetic acid (NTA) moieties that can complex histidine-tagged (His-tagged) proteins selectively and reversibly. Using fluorescence microscopy, IR spectroscopy, X-ray photoelectron spectroscopy, surface plasmon resonanace, and ellipsometry, we demonstrate that His-tagged green fluorescent protein can be immobilized on NTA brushes with high stability and loading. The loading saturation reached for NTA-POEGMA is higher than that for NTA-PHEMA because of increased swelling of the former brush. Despite this higher loading capacity, NTA-POEGMA remained highly protein-resistant, which shows its potential for “clean” and specific protein immobilization. Finally, we showed that the preserved protein resistance of NTA-POEGMA brushes can be used to generate well-defined binary biofunctional patterns via a simple protocol of incubations and washes. These patterns may find applications in cell arraying and screening.

  • 10. Gross, Jeremy
    et al.
    Passmore, Ian J
    Chung, Jade Cs
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Welch, Martin
    Universal soldier: Pseudomonas aeruginosa - an opportunistic generalist2013In: Frontiers in Biology, ISSN 1674-7984, Vol. 8, no 4, p. 387-394Article in journal (Refereed)
    Abstract [en]

    The opportunistic pathogen Pseudomonas aeruginosa commonly causes chronic and ultimately deadly lung infections in individuals with the genetic disease cystic fibrosis (CF). P. aeruginosa is metabolically diverse; it displays a remarkable ability to adapt to and successfully occupy almost any niche, including the ecologically complex CF lung. These P. aeruginosa lung infections are a fascinating example of microbial evolution within a "natural" ecosystem. Initially, P. aeruginosa shares the lung niche with a plethora of other microorganisms and is vulnerable to antibiotic challenges. Over time, adaptive evolution leads to certain commonly-observed phenotypic changes within the P. aeruginosa population, some of which render it resistant to antibiotics and apparently help it to out-compete the other species that co-habit the airways. Improving genomics techniques continue to elucidate the evolutionary mechanisms of P. aeruginosa within the CF lung and will hopefully identify new vulnerabilities in this robust and versatile pathogen. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg.

  • 11.
    Hakobyan, Shoghik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Barbero, David R.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Preparation of Antifouling Polymer Brushes Functionalized with Gallium Salicylidene Acylhydrazide ComplexesManuscript (preprint) (Other academic)
  • 12.
    Hakobyan, Shoghik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Boily, Jean-François
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Proton and gallium(III) binding properties of a biologically active salicylidene acylhydrazide2014In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 138, p. 9-15Article in journal (Refereed)
    Abstract [en]

    Bacterial biofilm formation causes a range of problems in our society, especially in health care. Salicylidene acylhydrazides (hydrazones) are promising antivirulence drugs targeting secretion systems used during bacterial infection of host cells. When mixed with the gallium ion they become especially potent as bacterial and biofilm growth-suppressing agents, although the mechanisms through which this occurs are not fully understood. At the base of this uncertainty lies the nature of hydrazone-metal interactions. This study addresses this issue by resolving the equilibrium speciation of hydrazone-gallium aqueous solutions. The protonation constants of the target 2-oxo-2-[N-(2,4,6-trihydroxy-benzylidene)-hydrazino]-acetamide (ME0163) hydrazone species and of its 2,4,6-trihydroxybenzaldehyde and oxamic acid hydrazide building blocks were determined by UV-visible spectrophotometry to achieve this goal. These studies show that the hydrazone is an excessively strong complexing agent for gallium and that its antivirulence properties are predominantly ascribed to monomeric 1:1Ga-ME0163 complexes of various Ga hydrolysis and ME0163 protonation states. The chelation of Ga(III) to the hydrazone also increased the stability of the compounds against acid-induced hydrolysis, making this group of compounds very interesting for biological applications where the Fe-antagonist action of both Ga(III) and the hydrazone can be combined for enhanced biological effect.

  • 13.
    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.

  • 14.
    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.
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Boily, Jean-François
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Influence of Chelation Strength and Bacterial Uptake of Gallium Salicylidene Acylhydrazide on Biofilm Formation and Virulence by Pseudomonas aeruginosa2016In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 160, p. 24-32Article in journal (Refereed)
    Abstract [en]

    Development of antibiotic resistance in bacteria causes major challenges for our society and has prompted a great need for new and alternative treatment methods for infection. One promising approach is to target bacterial virulence using for example salicylidene acylhydrazides (hydrazones). Hydrazones coordinate metal ions such as Fe(III) and Ga(III) through a five-membered and a six-membered chelation ring. One suggested mode of action is via restricting bacterial Fe uptake. Thus, it was hypothesized that the chelating strength of these substances could be used to predict their biological activity on bacterial cells. This was investigated by comparing Ga chelation strength of two hydrazone complexes, as well as bacterial Ga uptake, biofilm formation, and virulence in the form of production and secretion of a toxin (ExoS) by Pseudomonas aeruginosa. Equilibrium constants for deprotonation and Ga(III) binding of the hydrazone N′-(5-chloro-2-hydroxy-3-methylbenzylidene)-2,4-dihydroxybenzhydrazide (ME0329), with anti-virulence effect against P. aeruginosa, were determined and compared to bacterial siderophores and the previously described Ga(III) 2-oxo-2-[N-(2,4,6-trihydroxy-benzylidene)-hydrazino]-acetamide (Ga-ME0163) and Ga-citrate complexes. In comparison with these two complexes, it was shown that the uptake of Ga(III) was higher from the Ga-ME0329 complex. The results further show that the Ga-ME0329 complex reduced ExoS expression and secretion to a higher extent than Ga-citrate, Ga-ME0163 or the non-coordinated hydrazone. However, the effect against biofilm formation by P. aeruginosa, by the ME0329 complex, was similar to Ga-citrate and lower than what has been reported for Ga-ME0163.

  • 15. Kapadnis, Prashant B
    et al.
    Hall, Evan
    Ramstedt, Madeleine
    Department of Chemistry, University of Cambridge.
    Galloway, Warren R J D
    Welch, Martin
    Spring, David R
    Towards quorum-quenching catalytic antibodies2009In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 5, p. 538-540Article in journal (Refereed)
    Abstract [en]

    The development of a novel method to attenuate bacterial virulence is reported, which is based upon the use of designed transition-state analogues to select human catalytic antibodies capable of degrading bacterial quorum-sensing molecules.

  • 16. Kong, Dexu
    et al.
    Megone, William
    Nguyen, Khai D. Q.
    Di Cio, Stefania
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gautrot, Julien E.
    Protein nanosheet mechanics controls cell adhesion and expansion on low-viscosity liquids2018In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, no 3, p. 1946-1951Article in journal (Refereed)
    Abstract [en]

    Adherent cell culture typically requires cell spreading at the surface of solid substrates to sustain the formation of stable focal adhesions and assembly of a contractile cytoskeleton. However, a few reports have demonstrated that cell culture is possible on liquid substrates such as silicone and fluorinated oils, even displaying very low viscosities (0.77 cSt). Such behavior is surprising as low viscosity liquids are thought to relax much too fast (<ms) to enable the stabilization of focal adhesions (with lifetimes on the order of minutes to hours). Here we show that cell spreading and proliferation at the surface of low viscosity liquids are enabled by the self-assembly of mechanically strong protein nanosheets at these interfaces. We propose that this phenomenon results from the denaturation of globular proteins, such as albumin, in combination with the coupling of surfactant molecules to the resulting protein nanosheets. We use interfacial rheology and atomic force microscopy indentation to characterize the mechanical properties of protein nanosheets and associated liquid–liquid interfaces. We identify a direct relationship between interfacial mechanics and the association of surfactant molecules with proteins and polymers assembled at liquid–liquid interfaces. In addition, our data indicate that cells primarily sense in-plane mechanical properties of interfaces, rather than relying on surface tension to sustain spreading, as in the spreading of water striders. These findings demonstrate that bulk and nanoscale mechanical properties may be designed independently, to provide structure and regulate cell phenotype, therefore calling for a paradigm shift for the design of biomaterials in regenerative medicine.

  • 17.
    Krishnamoorthy, Mahentha
    et al.
    Institute of Bioengineering and School of Engineering and Materials Science, Queen Mary University of London, United Kingdom.
    Hakobyan, Shoghik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gautrot, Julien E.
    Institute of Bioengineering and School of Engineering and Materials Science, Queen Mary University of London, United Kingdom.
    Surface-initiated polymer brushes in the biomedical field: applications in membrane science, biosensing, cell culture, regenerative medicine and antibacterial coatings2014In: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 114, no 21, p. 10976-11026Article, review/survey (Refereed)
  • 18.
    Nakao, Ryoma
    et al.
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wai, Sun Nyunt
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Uhlin, Bernt Eric
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Enhanced biofilm formation by Escherichia coli LPS mutants defective in hep biosynthesis2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 12, p. e51241-Article in journal (Refereed)
    Abstract [en]

    Lipopolysaccharide (LPS) is the major component of the surface of Gram-negative bacteria and its polysaccharide portion is situated at the outermost region. We investigated the relationship between the polysaccharide portion of LPS and biofilm formation using a series of Escherichia coli mutants defective in genes earlier shown to affect the LPS sugar compositions. Biofilm formation by a deep rough LPS mutant, the hldE strain, was strongly enhanced in comparison with the parental strain and other LPS mutants. The hldE strain also showed a phenotype of increased auto-aggregation and stronger cell surface hydrophobicity compared to the wild-type. Similar results were obtained with another deep rough LPS mutant, the waaC strain whose LPS showed same molecular mass as that of the hldE strain. Confocal laser scanning microscopy (CLSM) analysis and biofilm formation assay using DNase I revealed that biofilm formation by the hldE strain was dependent on extracellular DNA. Furthermore, a loss of flagella and an increase in amount of outer membrane vesicles in case of the hldE strain were also observed by transmission electron microscopy and atomic force microscopy, respectively. In addition, we demonstrated that a mutation in the hldE locus, which alters the LPS structure, caused changes in both expression and properties of several surface bacterial factors involved in biofilm formation and virulence. We suggest that the implication of these results should be considered in the context of biofilm formation on abiotic surfaces, which is frequently associated with nosocominal infections such as the catheter-associated infections.

  • 19.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Chemistry.
    Chemical Processes at the Water-Manganite (γ-MnOOH) Interface2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The chemistry of mineral surfaces is of great importance in many different areas including natural processes occurring in oceans, rivers, lakes and soils. Manganese (hydr)oxides are one important group to these natural processes, and the thermodynamically most stable trivalent manganese (hydr)oxide, manganit (γ-MnOOH), is studied in this thesis.

    This thesis summarises six papers in which the surface chemistry of synthetic manganite has been investigated with respect to surface acid-base properties, dissolution, and adsorption of Cd(II) and the herbicide N-(phosphonomethyl)glycine (glyphosate, PMG). In these papers, a wide range of analysis techniques were used, including X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS) spectroscopy, Fourier transform infra-red (FTIR) spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), potentiometry, electrophoretic mobility measurements and wet chemical techniques, in order to obtain a more complete understanding of the different processes occurring at the manganite-water interface.

    From the combined use of these techniques, a 1-pKa acid-base model was established that is valid at pH>6. The model includes a Na+ interaction with the surface:

    =MnOH2+½ --> =MnOH-½ + H+ log β0 (intr.) = -8.20 = -pHiep

    =MnOH2+½ + Na+ --> =MnOHNa+½ + H+ log β0 (intr.) = -9.64

    At pH<6 the manganite crystals dissolve and disproportionate into pyrolusite (β-MnO2) and Mn(II)-ions in solution according to:

    2 γ-MnOOH + 2H+ --> β-MnO2 + Mn2+ + 2H2O log K0 = 7.61 ± 0.10

    The adsorption and co-adsorption of Cd(II) and glyphosate at the manganite surface was studied at pH>6. Cd(II) adsorption displays an adsorption edge at pH~8.5. Glyphosate adsorbs over the entire pH range, but the adsorption decreases with increasing pH. When the two substances are co-adsorbed, the adsorption of Cd(II) is increased at low pH but decreased at high pH. The adsorption of glyphosate is increased in the entire pH range in the presence of Cd(II). From XPS, FTIR and EXAFS it was found that glyphosate and Cd(II) form inner sphere complexes. The binary Cd(II)-surface complex is bonded by edge sharing of Mn and Cd octahedra on the (010) plane of manganite. Glyphosate forms inner-sphere complexes through an interaction between the phosphonate group and the manganite surface. The largest fraction of this binary glyphosate complex is protonated throughout the pH range. A ternary surface complex is also present, and its structure is explained as type B ternary surface complex (surface-glyphosate-Cd(II)). The chelating rings between the Cd(II) and glyphosate, found in aqueous complexes, are maintained at the surface, and the ternary complex is bound to the surface through the phosphonate group of the ligand.

  • 20. Ramstedt, Madeleine
    Polymer Brushes and Microorganisms2017In: Polymer and Biopolymer Brushes: for Materials Science and Biotechnology / [ed] Omar Azzaroni and Igal Szleifer, John Wiley & Sons, 2017, p. 515-552Chapter in book (Other academic)
  • 21.
    Ramstedt, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Andersson, Britt M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Surface properties of hydrous manganite (-MnOOH): A potentiometric, electroacoustic, and x-ray photoelectron spectroscopy study2004In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, no 19, p. 8224-8229Article in journal (Refereed)
    Abstract [en]

    The acid-base characteristics of the manganite (-MnOOH) surface have been studied at pH above 6, where dissolution is negligible. Synthetic microcrystalline particles of manganite were used in the experiments. From potentiometric titrations, electrophoretic mobility measurements, and X-ray photoelectron spectroscopy (XPS), a one pKa model was constructed that describes the observed behavior. The data show no ionic strength effect at pH < 8.2, which is the pH at the isoelectric point (pHiep), but ionic strength effects were visible above this pH. To explain these observations, Na+ ions were suggested to form a surface complex. The following equilibria were established: =MnOH2+1/2 =MnOH-1/2 + H+, log 0 (intr.) = -8.20; =MnOH2+1/2 + Na+ =MnOHNa+1/2 + H+, log 0 (intr.) = -9.64. The excess of Na+ at the surface was supported by XPS measurements of manganite suspensions containing 10 mM NaCl. The dielectric constant of synthetic manganite powder was also determined in this study.

  • 22.
    Ramstedt, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Carlsson, Erik
    Lövgren, Lars
    Umeå University, Faculty of Science and Technology, Chemistry.
    Aqueous geochemistry in the Udden pit lake, northern Sweden2003In: Applied Geochemistry, Vol. 18, no 1, p. 97-108Article in journal (Refereed)
    Abstract [en]

    The Udden pit lake in northern Sweden was studied from June 1998 to February 1999 in order to increase knowledge of the geochemistry in lakes created as a result of decommissioning open pit mines. The vertical water profile in the lake was sampled on 4 different occasions, in June, August, September and February. Water samples were analysed for total concentrations of Fe, As, Cu, Cd, Zn, Pb, Al, Ca, K, Mg, Na, Mn, S, Cl, N and P. Temperature, concentration of dissolved O2, conductivity, pH, and redox potential were measured in situ at different depths. Four layers could be observed in the lake during summer, and 3 layers during winter. A thermocline was observed during summer at a depth of 5 m and on all 4 occasions a halocline was observed at a depth of 20 m, and a redoxcline at 35 m. Oxygen concentration decreased dramatically at a depth of 20 m. pH increased downwards in the lake from 4.8 at the surface to 6.4 at the bottom of the lake. Geochemical processes occurring in the lake, the origins of the layers, the metal concentrations and the anion concentrations are discussed in this article.

  • 23.
    Ramstedt, Madeleine
    et al.
    Department of Chemistry, University of Cambridge.
    Cheng, Nan
    Azzaroni, Omar
    Mossialos, Dimitris
    Mathieu, Hans Jörg
    Huck, Wilhelm T S
    Synthesis and characterization of poly(3-sulfopropylmethacrylate) brushes for potential antibacterial applications2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 6, p. 3314-21Article in journal (Refereed)
    Abstract [en]

    This article describes the aqueous atom transfer radical polymerization synthesis of poly(3-sulfopropylmethacrylate) brushes onto gold and Si/SiO2 surfaces in a controlled manner. The effect of Cu(I)/Cu(II) ratio was examined, and a quartz crystal microbalance was used to study the kinetics of the brush synthesis. The synthesized brushes displayed a thickness from a few nanometers to several hundred nanometers and were characterized using atomic force microscopy, ellipsometry, Fourier transform infrared spectroscopy (FTIR), contact angle measurements, and X-ray photoelectron spectroscopy (XPS). The as-synthesized sulfonate brushes had very good ion-exchange properties for the ions tested in this study, i.e., Na+, K+, Cu2+, and Ag+. FTIR and XPS show that the metal ions are coordinating to sulfonate moieties inside the brushes. The brushes were easily loaded with silver ions, and the effect of silver ion concentration on silver loading of the brush was examined. The silver-loaded brushes were shown to be antibacterial toward both gram negative and gram positive bacteria. The silver leaching was studied through leaching experiments into water, NaNO3, and NaCl (physiological medium). The results from these leaching experiments are compared and discussed in the article.

  • 24.
    Ramstedt, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Ekstrand-Hammarström, Barbro
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Chemistry.
    Bucht, Anders
    Umeå University, Faculty of Medicine, Public Health and Clinical Medicine, Pulmonary Medicine.
    Österlund, Lars
    Welch, Martin
    Huck, Wilhelm T.S.
    Bacterial and mammalian cell response to poly(3-sulfopropyl methacrylate) brushes loaded with silver halide salts2009In: Biomaterials, Vol. 30, no 8, p. 1524-31Article in journal (Refereed)
    Abstract [en]

    This study investigates the antibacterial and cytotoxic effect of surfaces with sulphonate brushes containing silver salts. By using the same type of samples for both cytotoxicity and antibacterial studies, these two parameters could be compared in a controlled way. The silver was incorporated into the brush in four different forms to enable release of silver ions at different concentrations and different rates. It was found that although the surfaces displayed very good antibacterial properties in buffer solutions, this effect disappeared in systems with high protein content. Similarly, the silver-containing surfaces displayed cytotoxic effects in the absence of serum proteins but this effect was reduced in the presence of serum. The speciation of silver in the different solutions is discussed. Cytotoxic and antibacterial effects are compared at the different silver concentrations released. The implications of a concentration range where silver could be used to kill bacterial without harmful effects on mammalian cells are also discussed and questioned.

  • 25.
    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.

  • 26.
    Ramstedt, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hedlund, Tomas
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Fick, Jerker
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Jahnke, Isa
    Umeå University, Faculty of Social Sciences, Department of applied educational science. School of Information Science and Learning Technologies, University of Missouri, Columbia, MO, USA.
    Rethinking chemistry in higher education towards technology-enhanced problem-based learning2016In: Education Inquiry, ISSN 2000-4508, E-ISSN 2000-4508, Vol. 7, no 2, p. 115-135Article in journal (Refereed)
    Abstract [en]

    A range of factors can lead to situations where university courses have to be taught with a very small number of students. In this paper, we report on our experiences of a chemistry course that was especially designed to encourage learning in small groups of students (four to five per course). The course design included inquiry-based approaches, case methodology and problem-based learning concepts. The main goal was to enhance student motivation and to support them to become active agents (‘pro-sumers’). Technology was adopted to support students in their inquiry-based learning processes by using online logs, group wikis and quizzes and with sections of laboratory work. We explored student perceptions during the first 2 years in two courses. The students were, in general, very positive about the course and communicated that the technological tools along with the pedagogical design decisions had assisted them to different extents in their learning. Our conclusion is that such a design is appropriate for an advanced-level chemistry course with small numbers of students, and the course will continue to be given in this form.

  • 27.
    Ramstedt, Madeleine
    et al.
    Department of Chemistry, University of Cambridge.
    Houriet, Raymond
    Mossialos, Dimitris
    Haas, Dieter
    Mathieu, Hans Jörg
    Wet chemical silver treatment of endotracheal tubes to produce antibacterial surfaces2007In: Journal of biomedical materials research. Part B, Applied biomaterials, ISSN 1552-4973, Vol. 83, no 1, p. 169-80Article in journal (Refereed)
    Abstract [en]

    Mechanically ventilated patients in hospitals are subjected to an increased risk of acquiring nosocomial pneumonia that sometimes has a lethal outcome. One way to minimize the risk could be to make the surfaces on endotracheal tubes antibacterial. In this study, bacterial growth was inhibited or completely prevented by silver ions wet chemically and deposited onto the tube surface. Through the wet chemical treatment developed here, a surface precipitate was formed containing silver chloride and a silver stearate salt. The identity and morphology of the surface precipitate was studied using x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and x-ray powder diffraction. Leaching of silver ions into solution was examined, and bacterial growth on the treated surfaces was assayed using Pseudomonas aeruginosa wild type (PAO1) bacteria. Furthermore, the minimum inhibitory concentration of silver ions was determined in liquid- and solid-rich growth medium as 23 and 18 microM, respectively, for P. aeruginosa.

  • 28.
    Ramstedt, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Leone, Laura
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Persson, Per
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Cell wall composition of Bacillus subtilis changes as a function of pH and Zn2+ exposure: insights from cryo-XPS measurements2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 15, p. 4367-4374Article in journal (Refereed)
    Abstract [en]

    Bacteria play an important role in the biogeochemical cycling of metals in the environment. Consequently, there is an interest to understand how the bacterial surfaces interact with metals in solution and how this affects the bacterial surface. In this work we have used a surface-sensitive analysis technique, cryogenic X-ray photoelectron spectroscopy (cryo-XPS), to monitor the surface of Bacillus subtilis cells as a function of pH and Zn2+ content in saline solution. The objective of the study was twofold: (1) to investigate the agreement between two data treatment methods for XPS, as well as investigate to what extent sample pretreatment may influence XPS data of bacterial samples, and (2) to characterize how the surface chemistry of bacterial cells is influenced by different external conditions. (1) It was found that the two data treatment methods gave rise to comparable results. However, identical samples analyzed fast-frozen or dry exhibited larger differences in surface chemistry, indicating that sample pretreatment can to large extents influence the obtained surface composition of bacterial samples. (2) The bacterial cell wall (in fast-frozen samples) undergoes dramatic compositional changes with pH and with Zn2+ exposure. The compositional changes are interpreted as an adaptive metal resistance response changing the biochemical composition of the bacterial cell wall. These results have implications for how adsorption processes at the surface of bacterial cells are analyzed, understood, modeled, and predicted. 

  • 29.
    Ramstedt, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Nakao, Ryoma
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Nyunt Wai, Sun
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Uhlin, Bernt Eric
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Boily, Jean-Francois
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Monitoring surface chemistry changes in the bacterial cell wall: multivariate analysis of Cryo-X-ray photoelectron spectroscopy data2011In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 286, no 14, p. 12389-12396Article in journal (Refereed)
    Abstract [en]

    Gram-negative bacteria can alter the composition of the Lipopolysaccharide (LPS) layer of the outer membrane as a response to different growth conditions and external stimuli. These alterations can, for example, promote attachment to surfaces and biofilm formation. The changes occur in the outermost layer of the cell and may consequently influence interactions between bacterial cells and surrounding host tissue, as well as other surfaces. Microscopic analyses, fractionation of bacterial cells or other traditional microbiological assays have previously been used to study these alterations. These methods can, however, be time consuming and do not always give detailed chemical information about the bacterial cell surface. We here present an analytical method that provides chemical information on the outermost portion of bacterial cells with respect to protein, peptidoglycan, lipid and polysaccharide content. The method involves cryo-X-ray Photoelectron Spectroscopy (XPS) analyses of the outermost portion (within ~10 nm of the surface) of intact bacterial cells, followed by a multivariate curve resolution analysis of carbon spectra. It can be used as a tool for characterizing and monitoring variations in the chemical composition of bacterial cell walls or of isolated outer membrane vesicles, variations that result from e.g. mutations or external stimuli. The method enabled us to accurately predict the alterations in polysaccharide content and surface chemistries of a set of well characterized Escherichia coli LPS mutants. The described approach may moreover be applied to monitor surface chemical composition of other biological samples.

  • 30.
    Ramstedt, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Norgren, Caroline
    Umeå University, Faculty of Science and Technology, Chemistry.
    Shchukarev, Andrei
    Umeå University, Faculty of Science and Technology, Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Chemistry.
    Persson, Per
    Umeå University, Faculty of Science and Technology, Chemistry.
    Co-adsorption of cadmium(II) and glyphosate at the water–manganite (γ-MnOOH) interface2005In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 285, no 2, p. 493-501Article in journal (Refereed)
    Abstract [en]

    The co-adsorption of Cd(II) and glyphosate (N-(phosphonomethyl)glycine, PMG) at the manganite (γ-MnOOH) surface has been studied in the pH range 6–10 at 25 °C and with 0.1 M Na(Cl) as ionic medium. Batch adsorption experiments, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS) spectroscopy were used for the quantitative analysis and the determination of the molecular structure of the surface complexes. The adsorption of Cd(II) and PMG in the ternary Cd(II)–PMG–manganite system was compared with the adsorption in the binary Cd(II)–manganite and PMG–manganite systems. The formation of three inner sphere surface complexes was observed, a ternary Cd(II)–PMG–manganite complex, a binary Cd(II)–manganite complex and a binary PMG–manganite complex. The surface concentration of the ternary complex and the Cd(II)–manganite complex was more or less constant throughout the pH range studied. However, the surface concentration of the binary PMG–manganite complex decreased with increasing pH. The major part of the binary PMG–surface complex was protonated. The ternary surface complex displayed a type B structure (Cd(II)–PMG–manganite). The average Cd–Mn distance obtained from EXAFS (3.26 Å) indicates that the binary and ternary Cd(II)–surface complexes are formed by edge-sharing of Mn and Cd octahedra on the (010) plane of the manganite crystals.

  • 31.
    Ramstedt, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Norgren, Caroline
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sheals, Julia
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Persson, Per
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Thermodynamic and spectroscopic studies of cadmium(II)–N-(phosphonomethyl)glycine (PMG) complexes2004In: Inorganica Chimica Acta, ISSN 0020-1693, E-ISSN 1873-3255, Vol. 357, no 4, p. 1185-1192Article in journal (Refereed)
    Abstract [en]

    Speciation and equilibria in the H+–Cd2+N-(phosphonomethyl)glycine (PMG, H3L) system have been studied in 0.1 M Na(Cl) medium at 25.0 °C. Formation constants for a series of mononuclear complexes, CdHL, CdL, CdL2 4− and CdL(OH)2− were determined from potentiometric titrations. The structures of the predominating species CdL, and CdL2 4− in solution were investigated using EXAFS and IR spectroscopic techniques. In the 1:1 complex bonds are formed between the Cd(II) ion and all three donor groups (amino, carboxylate, phosphonate) of the PMG molecule resulting in two 5-membered chelate rings. At the remaining three of the corners of the distorted Cd(II) octahedra oxygens were found which are replaced by donor groups of a second PMG molecule in the 1:2 complex. Furthermore, a solid phase consisting of Cd9(PMG)6(H2O)12 · 6H2O crystals was synthesized and the crystal structure was determined. The structure consists of six CdL octahedra connected through a seventh Cd–O octahedron in the centre of the entity, with two additional Cd–O octahedra located at the apices of the unit formed.

    Speciation and equilibria in the H+–Cd2+N-(phosphonomethyl)glycine (PMG, H3L) system have been studied using potentiometry, and formation constants for CdHL, CdL, CdL2 4− and CdL(OH)2− were determined. The structures of CdL, and CdL2 4− in solution were investigated using EXAFS and IR spectroscopic techniques. The results indicated chelating PMG molecules forming two 5-membered chelate rings.

  • 32.
    Ramstedt, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Norgren, Caroline
    Umeå University, Faculty of Science and Technology, Chemistry.
    Sheals, Julia
    Umeå University, Faculty of Science and Technology, Chemistry.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Chemistry.
    Chemical speciation of N-(phosphonomethyl)glycine in solution and at mineral interfaces2004In: Surface and Interface Analysis, ISSN 0142-2421, Vol. 36, no 8, p. 1074-7Article in journal (Refereed)
    Abstract [en]

    The chemical speciation of the zwitterionic compound N-(phosphonomethyl)glycine (PMG) was studied in solution and at the mineral/water interface at different pH. Results from vacuum techniques such as XPS were compared with previously published conventional batch experiments. It was shown that by keeping the samples frozen during XPS analyses it was possible to keep a water interface. The frozen interface enables studies of the protonation of the nitrogen group which has previously been difficult using XPS. The protonation in frozen solutions was compared with literature data and the differences discussed. Furthermore, the speciation of PMG at the surface of manganite (-MnOOH) and goethite (-FeOOH) was studied. It was found that at least one of the protonation constants for surface-bound PMG differs significantly from the protonation constants in a pure PMG solution. The formation of different surface complexes is discussed together with differences between the sorption capacities of PMG onto the minerals studied.

  • 33.
    Ramstedt, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ribeiro, Isabel A. C.
    Bujdakova, Helena
    Mergulhão, Filipe J. M.
    Jordao, Luisa
    Thomsen, Peter
    Alm, Martin
    Burmølle, Mette
    Vladkova, Todorka
    Can, Fusun
    Reches, Meital
    Riool, Martijn
    Barros, Alexandre
    Reis, Rui L.
    Meaurio, Emilio
    Kikhney, Judith
    Moter, Annette
    Zaat, Sebastian A. J.
    Sjollema, Jelmer
    Evaluating Efficacy of Antimicrobial and Antifouling Materials for Urinary Tract Medical Devices: Challenges and Recommendations2019In: Macromolecular Bioscience, ISSN 1616-5187, E-ISSN 1616-5195, Vol. 19, no 5, article id 1800384Article, review/survey (Refereed)
    Abstract [en]

    In Europe, the mean incidence of urinary tract infections in intensive care units is 1.1 per 1000 patient‐days. Of these cases, catheter‐associated urinary tract infections (CAUTI) account for 98%. In total, CAUTI in hospitals is estimated to give additional health‐care costs of £1–2.5 billion in the United Kingdom alone. This is in sharp contrast to the low cost of urinary catheters and emphasizes the need for innovative products that reduce the incidence rate of CAUTI. Ureteral stents and other urinary‐tract devices suffer similar problems. Antimicrobial strategies are being developed, however, the evaluation of their efficacy is very challenging. This review aims to provide considerations and recommendations covering all relevant aspects of antimicrobial material testing, including surface characterization, biocompatibility, cytotoxicity, in vitro and in vivo tests, microbial strain selection, and hydrodynamic conditions, all in the perspective of complying to the complex pathology of device‐associated urinary tract infection. The recommendations should be on the basis of standard assays to be developed which would enable comparisons of results obtained in different research labs both in industry and in academia, as well as provide industry and academia with tools to assess the antimicrobial properties for urinary tract devices in a reliable way.

  • 34.
    Ramstedt, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Analysis of bacterial cell surface chemical composition using cryogenic X-ray photoelectron spectroscopy2016In: Bacterial cell wall homeostasis: methods and protocols / [ed] Hee-Jeon Hong, New York, NY: Humana Press, 2016, p. 215-223Chapter in book (Other academic)
    Abstract [en]

    This chapter describes a method for measuring the average surface chemical composition with respect to lipids, polysaccharides, and peptides (protein + peptidoglycan) for the outer part of the bacterial cell wall. Bacterial cultures grown over night are washed with a buffer or saline at controlled pH. The analysis is done on fast-frozen bacterial cell pellets obtained after centrifugation, and the analysis requires access to X-ray photoelectron spectroscopy instrumentation that can perform analyses at cryogenic temperatures (for example using liquid nitrogen). The method can be used to monitor changes in the cell wall composition following environmental stimuli or genetic mutations. The data obtained originate from the outermost part of the cell wall. Thus, it is expected that for gram-negative bacteria only the outer membrane and part of the periplasmic peptidoglycan layer is probed during analysis, and for gram-positive bacteria only the top nanometers of the peptidoglycan layer of the cell wall is monitored.

  • 35.
    Ramstedt, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Chemistry.
    Characterization of hydrous manganite (-MnOOH) surfaces - an XPS study2002In: Surface and Interface Analysis, Vol. 34, no 1, p. 632-6Article in journal (Refereed)
    Abstract [en]

    Crystalline manganite (-MnOOH) has been synthesized and characterized using x-ray diffraction and high-resolution transmission electron microscopy techniques. The surface composition was studied with XPS between pH 0.4 and 11. Special pre-cooling procedures were developed to keep the manganite/water interface intact before and during XPS measurements. The O/OH group ratio differs between pH 6 and 11, in agreement with the acid/base characteristics of the surface. Below pH 6, on the other hand, drastic changes can be seen in the O 1s spectra due to dissolution of manganite. Possibly the interaction of OH groups with H+ in acidic suspensions is a first step leading to dissolution. The surface charge arising at high and low pH is compensated by the counter-ions Na+ and Cl-, respectively. The XPS spectra are presented and discussed in terms of the mechanisms for surface complexation and dissolution processes.

  • 36.
    Ramstedt, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Sjöberg, Staffan
    Low pH Phase Transformation and Proton Promoted Dissolution of Hydrous Manganite (γ-MnOOH)Manuscript (Other (popular science, discussion, etc.))
  • 37.
    Ramstedt, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Sjöberg, Staffan
    Umeå University, Faculty of Science and Technology, Chemistry.
    Phase Transformations and Proton Promoted Dissolution of Hydrous Manganite (γ-MnOOH)2005In: Aquatic Geochemistry, ISSN 1380-6165, Vol. 11, no 4, p. 413-31Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to describe the proton promoted disproportion of synthetic manganite (gamma-MnOOH) and to characterise the resulting phase transformations. The solution and remaining solid phase after disproportionation was analysed by techniques including atomic absorbance spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). In suspensions with pH between 5 and 7, -log[H+] was monitored for 17 months and equilibrium constants were determined at 9, 12 and 17 months of reaction time for the following reaction (25 degrees C, 0.1 M (Na)NO3):

    2 gamma-MnOOH+2H(+) reversible arrow Mn2+ + 2H(2)O

    The formed MnO2 ages with time and the equilibrium constant for a metastable phase (ramsdellite or nsutite) as well as the most stable phase, pyrolusite (beta-MnO2), was determined. Furthermore, combined pH and pe (Eh) measurements were performed to study the equilibrium;

    gamma-MnOOH(s) reversible arrow beta-MnO2(s)+H+ + e(-)

    Real-time AFM measurements of the dissolution showed shrinkage of the length of the manganite needles with time (2 hours). After 1 week SEM images showed that this decreased length also was followed by a reduced thickness of the manganite needles. From the SEM images the morphology of the formed Mn(IV) oxides was studied. At pH 2.6, pyrolusite (beta-MnO2) and MnCl2 were found in the XRD patterns. Throughout the pH range there were indications of ramsdellite (MnO1.97) in the XRD patterns, which coincided with the existence of a fraction of needle shaped crystals with smaller dimensions (compared to manganite) in the SEM images. These observations together with the long term dissolution experiments suggest that the dissolution of manganite initially forms a ramsdellite or nsutite phase that over time rearranges to form pyrolusite.

  • 38.
    Ruhal, Rohit
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Rzhepishevska, Olena
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Boulanger, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Barbero, David R.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wai, Sun Nyunt
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Uhlin, Bernt Eric
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    A multivariate approach to correlate bacterial surface properties to biofilm formation by lipopolysaccharide mutants of Pseudomonas aeruginosa2015In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 127, no 0, p. 182-191Article in journal (Refereed)
    Abstract [en]

    Abstract Bacterial biofilms are involved in various medical infections and for this reason it is of great importance to better understand the process of biofilm formation in order to eradicate or mitigate it. It is a very complex process and a large range of variables have been suggested to influence biofilm formation. However, their internal importance is still not well understood. In the present study, a range of surface properties of Pseudomonas aeruginosa lipopolysaccharide mutants were studied in relation to biofilm formation measured in different kinds of multi-well plates and growth conditions in order to better understand the complexity of biofilm formation. Multivariate analysis was used to simultaneously evaluate the role of a range of physiochemical parameters under different conditions. Our results suggest the presence of serum inhibited biofilm formation due to changes in twitching motility. From the multivariate analysis it was observed that the most important parameters, positively correlated to biofilm formation on two types of plates, were high hydrophobicity, near neutral zeta potential and motility. Negative correlation was observed with cell aggregation, as well as formation of outer membrane vesicles and exopolysaccharides. This work shows that the complexity of biofilm formation can be better understood using a multivariate approach that can interpret and rank the importance of different factors being present simultaneously under several different environmental conditions, enabling a better understanding of this complex process.

  • 39.
    Rzhepishevska, Olena
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ekstrand-Hammarström, Barbro
    Swedish Defence Research Institute (FOI), Umeå, Sweden .
    Popp, Maximilian
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bucht, Anders
    Swedish Defence Research Institute (FOI), Umeå, Sweden .
    Sjöstedt, Anders
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Antti, Henrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The antibacterial activity of Ga3+ is influenced by Llgand complexation as well as the bacterial carbon source2011In: Antimicrobial Agents and Chemotherapy, ISSN 0066-4804, E-ISSN 1098-6596, Vol. 55, no 12, p. 5568-5580Article in journal (Refereed)
    Abstract [en]

    Gallium ions have previously been shown to exhibit antibacterial and antibiofilm properties. In this study we report differential bactericidal activity of two gallium complexes; gallium desferrioxamine B (Ga-DFOB) and gallium citrate (Ga-cit). Modeling of gallium speciation in growth medium showed that DFOB and citrate both can prevent precipitation of Ga(OH)(3), but some precipitation can occur above pH 7 with citrate. Despite this, Ga-cit inhibitory concentrations (IC(90)) were lower than those of Ga-DFOB for clinical isolates of Pseudomonas aeruginosa, and several reference strains of other bacterial species. Treatment with Ga compounds mitigated damage inflicted on murine J774 macrophage-like cells infected with P. aeruginosa PAO1. Again, Ga-cit showed more potent mitigation than did Ga-DFOB. Ga was also taken up more efficiently by P. aeruginosa in the form of Ga-cit than in the form of Ga-DFOB. Neither Ga-cit nor Ga-DFOB was toxic to several human cell lines tested and no pro-inflammatory activity was detected in human lung epithelial cells after exposure in vitro. Metabolomic analysis was used to delineate the effects of Ga-cit on the bacterial cell. Exposure to Ga resulted in lower concentrations of glutamate, a key metabolite for P. aeruginosa, and of many amino acids, indicating that Ga affects various biosynthesis pathways. Altered protein expression profile in presence of Ga-cit suggested that some compensatory mechanisms were activated in the bacterium. Furthermore, the antibacterial effect of Ga was shown to vary depending on the carbon source, which has importance in the context of medical applications of gallium.

  • 40.
    Rzhepishevska, Olena
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hakobyan, Shoghik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ekstrand-Hammarström, Barbro
    Swedish Defense Research Institute (FOI), Umeå, Sweden.
    Nygren, Yvonne
    Swedish Defense Research Institute (FOI), Umeå, Sweden.
    Karlsson, Torbjörn
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Bucht, Anders
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Pulmonary Medicine. Swedish Defense Research Institute (FOI), Umeå, Sweden.
    Elofsson, Mikael
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Boily, Jean-François
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The gallium(III)-salicylidene acylhydrazide complex shows synergistic anti-biofilm effect and inhibits toxin production by Pseudomonas aeruginosa2014In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 138, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Bacterial biofilms cause a range of problems in many areas and especially in health care. Biofilms are difficult to eradicate with traditional antibiotics and consequently there is a need for alternative ways to prevent and/or remove bacterial biofilms. Furthermore, the emergence of antibiotic resistance in bacteria creates a challenge to find new types of antibiotics with a lower evolutionary pressure for resistance development. One route to develop such drugs is to target the so called virulence factors, i.e. bacterial systems used when bacteria infect a host cell. This study investigates synergy effects between Ga(III) ions, previously reported to suppress biofilm formation and growth in bacteria, and salicylidene acylhydrazides (hydrazones) that have been proposed as antivirulence drugs targeting the type three secretion system used by several Gram-negative pathogens, including Pseudomonas aerugionosa, during bacterial infection of host cells. A library of hydrazones was screened for: Fe(III) binding, enhanced anti-biofilm effect with Ga(III) on P. aeruginosa, and low cytotoxicity to mammalian cells. The metal coordination for the most promising ligand, 2-Oxo-2-[N-(2,4,6-trihydroxy-benzylidene)-hydrazino]-acetamide (ME0163) with Ga(III) was investigated using extended X-ray absorption fine structure spectroscopy as well as density functional theory. The results showed that Ga(III) chelates the hydrazone with 5- and 6-membered chelating rings, and that the Ga(III)-ME0163 complex enhanced the antibiofilm effect of Ga(III) while suppressing the type three secretion system in P. aeruginosa. The latter effect was not observed for the hydrazone alone and was similar for Ga(III)-citrate and Ga(III)-ME0163 complexes, indicating that the inhibition of virulence was caused by Ga(III).

  • 41.
    Rzhepishevska, Olena
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hakobyan, Shoghik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ruhal, Rohit
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gautrot, Julien
    Barbero, David
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    The surface charge of anti-bacterial coatings alters motility and biofilm architecture2013In: Journal of Biomaterials Science. Polymer Edition, ISSN 0920-5063, E-ISSN 1568-5624, Vol. 1, no 6, p. 589-602Article in journal (Refereed)
    Abstract [en]

    Bacterial biofilms affect many areas of human activity including food processing, transportation, public infrastructure, and most importantly healthcare. This study addresses the prevention of biofilms and shows that the surface charge of an abiotic substrate influences bacterial motility as well as the morphology and physiology of the biofilm. Grafting-from polymerisation was used to create polymer brush surfaces with different characteristics, and the development of Pseudomonas aeruginosa biofilms was followed using confocal microscopy. Interestingly, two types of biofilms developed on these surfaces: mushroom structures with high levels of cyclic diguanylate (c-di-GMP) were found on negatively charged poly (3-sulphopropylmethacrylate) (SPM) and zwitterionic poly (2-(methacryloyloxy)ethyl)dimethyl-3-sulphoproyl) ammonium hydroxide) (MEDSAH), while flat biofilms developed on glass, positively charged poly (2-(methacryloyloxy)-ethyl trimethyl ammonium chloride) (METAC), protein-repellent poly oligo(ethylene glycol methyl ether methacrylate) (POEGMA) and hydrophobic polymethylmethacrylate (PMMA). The results show that of all the surfaces studied, overall the negatively charged polymer brushes were most efficient in reducing bacterial adhesion and biofilm formation. However, the increased level of regulatory c-di-GMP in mushroom structures suggests that bacteria are capable of a quick physiological response when exposed to surfaces with varying physicochemical characteristics enabling some bacterial colonization also on negatively charged surfaces.

  • 42.
    Rzhepishevska, Olena I.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Limanska, Nataliia
    Galkin, Mykola
    Lacoma, Alicia
    Lundquist, Margaretha
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sokol, Dmytro
    Hakobyan, Shoghik
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Queen Mary University of London, London, UK.
    Sjöstedt, Anders
    Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
    Prat, Cristina
    Ramstedt, Madeleine
    Umeå University, Faculty of Science and Technology, Department of Chemistry.