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  • 1.
    Benjamins, Jan-Willem
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Mechanisms behind the Stabilizing Action of Cellulose Nanofibrils in Wet-Stable Cellulose Foams2015In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 16, no 3, p. 822-831Article in journal (Refereed)
  • 2. Besharat, Z.
    et al.
    Wakeham, D.
    Johnson, C. M.
    Luengo, G. S.
    Greaves, A.
    Odnevall Wallinder, I.
    Göthelid, M.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Department of Surface and Corrosion Science, School of Chemical Science and Engineering, KTH Royal Institute of Technology.
    Mixed monolayers of alkane thiols with polar terminal group on gold: Investigation of structure dependent surface properties2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 484, p. 279-290Article in journal (Refereed)
    Abstract [en]

    Adsorption of thiols with cationic or anionic terminal group on gold has been studied from mixed solutions of 11-Amino-1-undecanethiol (AUT) and 3-Mercaptopropionic acid (MPA) using Quartz Crystal Microbalance with Dissipation (QCM-D), X-ray Photoelectron Spectroscopy (XPS), atomic force microscopy (AFM) and contact angles. The goal is to probe the nature of such layers, and the additivity or otherwise of the pH responsiveness, with a view to evaluate their suitability as smart materials. For each of the two pure (unmixed) cases, ordered molecular monolayers are formed with sulfur binding to gold and the alkane chain pointing out from the surface as expected. Adsorption from the thiol mixtures, however, leads to a more complex behaviour. The surface concentration of thiols from the mixtures, as determined by QCM-D, is considerably lower than for the pure cases and it reaches a minimum at a 3:1 MPA/AUT relative concentration in the solution. The XPS results confirm a reduction in adsorbed amount in mixtures with the lowest overall intensity for the 3:1 ratio. Monolayers formed from mixtures display a wettability which is much lower and less pH sensitive. Collectively these results confirm that for adsorption from mixed systems, the configuration is completely different. Complex formation in the mixed solutions leads to the adsorption of molecules parallel to the surface in an axially in-plane configuration. This parallel layer of thiols is mechanically relatively robust to nano-shaving based on AFM measurements. These results will have a significant impact on the design of biomimetic surface coatings particularly when mixtures of oppositely charged molecules are present on the surface, as is commonly the case in biological, proteinaceous surfaces (e.g. hair and skin).

  • 3.
    Boge, Lukas
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Department of Chemical and Chemical Engineering, Applied Chemistry, Chalmers University of Technology.
    Bysell, Helena
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Ringstad, Lovisa
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Wennman, David
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Process Development, Analys och fastfas.
    Umerska, A.
    Cassisa, V.
    Eriksson, J.
    Joly-Guillou, M. -L
    Edwards, K.
    Andersson, M.
    Lipid-based liquid crystals as carriers for antimicrobial peptides: Phase behavior and antimicrobial effect2016In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, no 17, p. 4217-4228Article in journal (Refereed)
    Abstract [en]

    The number of antibiotic-resistant bacteria is increasing worldwide, and the demand for novel antimicrobials is constantly growing. Antimicrobial peptides (AMPs) could be an important part of future treatment strategies of various bacterial infection diseases. However, AMPs have relatively low stability, because of proteolytic and chemical degradation. As a consequence, carrier systems protecting the AMPs are greatly needed, to achieve efficient treatments. In addition, the carrier system also must administrate the peptide in a controlled manner to match the therapeutic dose window. In this work, lyotropic liquid crystalline (LC) structures consisting of cubic glycerol monooleate/water and hexagonal glycerol monooleate/oleic acid/water have been examined as carriers for AMPs. These LC structures have the capability of solubilizing both hydrophilic and hydrophobic substances, as well as being biocompatible and biodegradable. Both bulk gels and discrete dispersed structures (i.e., cubosomes and hexosomes) have been studied. Three AMPs have been investigated with respect to phase stability of the LC structures and antimicrobial effect: AP114, DPK-060, and LL-37. Characterization of the LC structures was performed using small-angle X-ray scattering (SAXS), dynamic light scattering, ζ-potential, and cryogenic transmission electron microscopy (Cryo-TEM) and peptide loading efficacy by ultra performance liquid chromatography. The antimicrobial effect of the LCNPs was investigated in vitro using minimum inhibitory concentration (MIC) and time-kill assay. The most hydrophobic peptide (AP114) was shown to induce an increase in negative curvature of the cubic LC system. The most polar peptide (DPK-060) induced a decrease in negative curvature while LL-37 did not change the LC phase at all. The hexagonal LC phase was not affected by any of the AMPs. Moreover, cubosomes loaded with peptides AP114 and DPK-060 showed preserved antimicrobial activity, whereas particles loaded with peptide LL-37 displayed a loss in its broad-spectrum bactericidal properties. AMP-loaded hexosomes showed a reduction in antimicrobial activity.

  • 4. Cooper, P. K.
    et al.
    Li, H.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Department of Surface and Corrosion Science, School of Chemical Science and Engineering, KTH Royal Institute of Technology.
    Webber, G. B.
    Atkin, R.
    Tribotronic control of friction in oil-based lubricants with ionic liquid additives2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 34, p. 23657-23662Article in journal (Refereed)
    Abstract [en]

    Atomic force microscopy (AFM) reveals that tribotronic control of friction using an external potential applied to a gold surface is possible for ionic liquid (IL) concentrations as low as 5 mol% in hexadecane. The IL used is trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate, in which both the cation and anion have surfactant-like structures, and is miscible with hexadecane in all proportions. For IL concentrations less than 5 mol% friction does not vary with applied potential, but for 5 mol% and above changing the potential changes the composition of the IL boundary layer from cation-enriched (negative potentials) to anion-enriched (positive potentials). As the lubricities of the cation-rich and anion-rich boundary layers differ, this enables active control of friction in oil-based lubricants.

  • 5. Duvefelt, K.
    et al.
    Olofsson, U.
    Johannesson, C. M.
    Skedung, Lisa
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Model for contact between finger and sinusoidal plane to evaluate adhesion and deformation component of friction2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 96, p. 389-394Article in journal (Refereed)
    Abstract [en]

    One of the main parameters affecting finger friction, friction-induced vibrations in the finger, and consequently tactility is surface topography. Recently Skedung et al. performed finger friction measurements on fine controlled surfaces. These surfaces were sinusoidal with wavelengths from 0.27 to 8.8 μm and amplitudes from 0.007 to 6 μm. Building on those tests an analytical model for the contact was developed to explain the differences in friction coefficient. The contact was modelled as trapezoids in a circular pattern pressed against a sinusoidal plane. Results showed that the calculated contact area and therefore friction coefficient corresponded well with the measurements. This model can be used to see how the different surface parameters influence friction.

  • 6. Gårdebjer, S.
    et al.
    Andersson, Martin
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Engström, J.
    Restorp, P.
    Persson, M.
    Larsson, Anders
    Using Hansen solubility parameters to predict the dispersion of nano-particles in polymeric films2016In: Polymer Chemistry, ISSN 1759-9954, E-ISSN 1759-9962, Vol. 7, no 9, p. 1756-1764Article in journal (Refereed)
    Abstract [en]

    We suggest a rough and straightforward method to predict the dispersibility of modified cellulose nanocrystals (CNC) in nanocomposites using Hansen solubility parameters (HSP). The surface of CNC was modified using a novel approach where Y-shaped substituents with two different carbon chain lengths were attached to the surface. Approximate HSP values were calculated for the modified CNC, and dispersions of unmodified and modified CNC in solvents with varying HSPs were studied. The best dispersibility was observed in dichloromethane, when the CNC surface was modified with longer carbon chains. Dichloromethane has HSP similar to low-density polyethylene (LDPE). Nanocomposites with both unmodified and modified CNC were produced. The materials with modified CNC showed increased adhesion between the filler and the matrix, followed by a decreased water permeability compared to unmodified CNC, suggesting a better dispersibility of modified CNC in LDPE and confirming the usefulness of this approach.

  • 7. Hedberg, J.
    et al.
    Karlsson, H. L.
    Hedberg, Y.
    Blomberg, E.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. KTH Royal Institute of Technology, School of Chemical Science and Engineering, Division of Surface and Corrosion Science.
    Odnevall Wallinder, I.
    The importance of extracellular speciation and corrosion of copper nanoparticles on lung cell membrane integrity2016In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 141, p. 291-300Article in journal (Refereed)
    Abstract [en]

    Copper nanoparticles (Cu NPs) are increasingly used in various biologically relevant applications and products, e.g., due to their antimicrobial and catalytic properties. This inevitably demands for an improved understanding on their interactions and potential toxic effects on humans. The aim of this study was to investigate the corrosion of copper nanoparticles in various biological media and to elucidate the speciation of released copper in solution. Furthermore, reactive oxygen species (ROS) generation and lung cell (A549 type II) membrane damage induced by Cu NPs in the various media were studied. The used biological media of different complexity are of relevance for nanotoxicological studies: Dulbecco's modified eagle medium (DMEM), DMEM+ (includes fetal bovine serum), phosphate buffered saline (PBS), and PBS + histidine. The results show that both copper release and corrosion are enhanced in DMEM+, DMEM, and PBS + histidine compared with PBS alone. Speciation results show that essentially no free copper ions are present in the released fraction of Cu NPs in neither DMEM+, DMEM nor histidine, while labile Cu complexes form in PBS. The Cu NPs were substantially more membrane reactive in PBS compared to the other media and the NPs caused larger effects compared to the same mass of Cu ions. Similarly, the Cu NPs caused much more ROS generation compared to the released fraction only. Taken together, the results suggest that membrane damage and ROS formation are stronger induced by Cu NPs and by free or labile Cu ions/complexes compared with Cu bound to biomolecules.

  • 8. Hedberg, Y. S.
    et al.
    Pettersson, M.
    Pradhan, S.
    Odnevall Wallinder, I.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Department of Surface and Corrosion Science, School of Chemical Science and Engineering, KTH Royal Institute of Technology.
    Persson, C.
    Can Cobalt(II) and Chromium(III) ions released from joint prostheses influence the friction coefficient?2015In: ACS Biomaterial Science and Engineering, ISSN 2373-9878, Vol. 1, no 8, p. 617-620Article in journal (Refereed)
    Abstract [en]

    Cobalt chromium molybdenum alloys (CoCrMo) are commonly used as articulating components in joint prostheses. In this tribocorrosive environment, wear debris and metal ionic species are released and interact with proteins, possibly resulting in protein aggregation. This study aimed to investigate whether this could have an effect on the friction coefficient in a typical material couple, namely CoCrMo-on-polyethylene. It was confirmed that both Co(II) and Cr(III) ions, and their combination, at concentrations relevant for the metal release situation, resulted in protein aggregation and its concomitant precipitation, which increased the friction coefficient. Future studies should identify the clinical importance of these findings.

  • 9. Hedberg, Y. S.
    et al.
    Pradhan, S.
    Cappellini, F.
    Karlsson, M. -E
    Blomberg, Eva
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Department of Chemistry, Surface and Corrosion Science, KTH Royal Institute of Technology.
    Karlsson, H. L.
    Odnevall Wallinder, I.
    Hedberg, J. F.
    Electrochemical surface oxide characteristics of metal nanoparticles (Mn, Cu and Al) and the relation to toxicity2016In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 212, p. 360-371Article in journal (Refereed)
    Abstract [en]

    Most metal nanoparticles (NPs), except noble metal NPs, rapidly form a thin surface oxide in ambient conditions. The protective properties of these oxides improve or worsen depending on the environment, e.g., the human lung. Several properties, including the chemical/electrochemical stability and defect density, determine the capacity of these surface oxides to hinder the bulk metal from further oxidation (corrosion). The aim of this study was to investigate whether electrochemical surface oxide characterization of non-functionalized base metal NPs of different characteristics (Al, Mn and Cu) can assist in understanding their bioaccessibility (metal release) in cell media (DMEM+) and their cytotoxic properties following exposure in lung epithelial (A549) cells. The composition and valence states of surface oxides of metal NPs and their electrochemical activity were investigated using an electrochemical technique based on a graphite paste electrode to perform cyclic voltammetry in buffer solutions and open circuit potential measurements in DMEM+. The electrochemical surface oxide characterization was complemented and verified by Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The open circuit potential trends in DMEM+ correlated well with metal release results in the same solution, and provided information on the kinetics of oxide dissolution in the case of Cu NPs. Extensive particle agglomeration in cell medium (DMEM+) was observed by means of photon-cross correlation spectroscopy for all metal NPs, with sedimentation taking place very quickly. As a consequence, measurements of the real dose of added non-functionalized metal NPs to cell cultures for cytotoxicity testing from a sonicated stock solution were shown necessary. The cytotoxic response was found to be strongly correlated to changes in physico-chemical and electrochemical properties of the surface oxides of the metal NPs, the most potent being Cu NPs, followed by Mn NPs. No cytotoxicity was observed for Al NPs. The electrochemical surface oxide characterization corresponded well with other tools commonly used for nanotoxicological characterization and provided additional information.

  • 10.
    Hillerström, Anna
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Production of Biodegradable Foams Using Supercritical CO22014In: Polymer-plastics technology and engineering (Softcover ed.), ISSN 0360-2559, E-ISSN 1525-6111, Vol. 53, no 11, p. 1169-1177Article in journal (Refereed)
  • 11.
    Hillerström, Anna
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Andersson, Martin
    Solvent strategies for loading and release in mesoporous silica2015In: Colloid and Interface Science Communications, ISSN 2215-0382, Vol. 83, no Nov, p. 5-8Article in journal (Refereed)
  • 12. Hjalmarsson, N.
    et al.
    Atkin, R.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Department of Surface and Corrosion Science, School of Chemical Science and Engineering, KTH Royal Institute of Technology.
    Effect of Lithium ions on rheology and interfacial forces in Ethylammonium Nitrate and Ethanolammonium Nitrate2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 47, p. 26960-26967Article in journal (Refereed)
    Abstract [en]

    The effect of added Li+ to two ionic liquids (ILs), ethylammonium nitrate (EAN) and ethanolammonium nitrate (EtAN), has been investigated using rheology and colloidal probe atomic force microscopy (AFM). Rheology data revealed a complex viscosity dependence that can be ascribed to the different bulk nanostructures. AFM force curves revealed steps for the neat ILs, analogous to those in previous studies. The addition of Li+ broadened the steps, which is likely an effect of ion clusters formed. Friction measurements corroborate this data and also showed that the structure of EtAN is much more prone to change as Li+ is added. These results demonstrate the complex behavior of ILs on interfaces and the effect of perturbing such interactions. (Graph Presented).

  • 13. Hjalmarsson, N.
    et al.
    Atkin, R.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Surface and Corrosion Science, KTH Royal Institute of Technology.
    Is the boundary layer of an ionic liquid equally lubricating at higher temperature?2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 13, p. 9232-9239Article in journal (Refereed)
    Abstract [en]

    Atomic force microscopy has been used to study the effect of temperature on normal forces and friction for the room temperature ionic liquid (IL) ethylammonium nitrate (EAN), confined between mica and a silica colloid probe at 25 °C, 50 °C, and 80 °C. Force curves revealed a strong fluid dynamic influence at room temperature, which was greatly reduced at elevated temperatures due to the reduced liquid viscosity. A fluid dynamic analysis reveals that bulk viscosity is manifested at large separation but that EAN displays a nonzero slip, indicating a region of different viscosity near the surface. At high temperatures, the reduction in fluid dynamic force reveals step-like force curves, similar to those found at room temperature using much lower scan rates. The ionic liquid boundary layer remains adsorbed to the solid surface even at high temperature, which provides a mechanism for lubrication when fluid dynamic lubrication is strongly reduced. The friction data reveals a decrease in absolute friction force with increasing temperature, which is associated with increased thermal motion and reduced viscosity of the near surface layers but, consistent with the normal force data, boundary layer lubrication was unaffected. The implications for ILs as lubricants are discussed in terms of the behaviour of this well characterised system.

  • 14. Hjalmarsson, N.
    et al.
    Wallinder, D.
    Glavatskih, S.
    Atkin, R.
    Aastrup, T.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Department of Surface and Corrosion Science, School of Chemical Science and Engineering, KTH Royal Institute of Technology.
    Weighing the surface charge of an ionic liquid2015In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 7, no 38, p. 16039-16045Article in journal (Refereed)
    Abstract [en]

    Electrochemical quartz crystal microbalance has been used to measure changes in the composition of the capacitive electrical double layer for 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)-trifluorophosphate, an ionic liquid, in contact with a gold electrode surface as a function of potential. The mass difference between the cation and anion means that the technique can effectively "weigh" the surface charge accurately with high temporal resolution. This reveals quantitatively how changing the potential alters the ratio of cations and anions associated with the electrode surface, and thus the charge per unit area, as well as the kinetics associated with these interfacial processes. The measurements reveal that it is diffusion of co-ions into the interfacial region rather than expulsion of counterions that controls the relaxation. The measured potential dependent double layer capacitance experimentally validates recent theoretical predictions for counterion overscreening (low potentials) and crowding (high potentials) at electrode surfaces. This new capacity to quantitatively measure ion composition is critical for ionic liquid applications ranging from batteries, capacitors and electrodeposition through to boundary layer structure in tribology, and more broadly provides new insight into interfacial processes in concentrated electrolyte solutions.

  • 15.
    Kronberg, Bengt
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    The hydrophobic effect2016In: Current Opinion in Colloid & Interface Science, ISSN 1359-0294, E-ISSN 1879-0399, Vol. 22, p. 14-22Article, review/survey (Refereed)
    Abstract [en]

    Abstract This review is a brief discussion on the development of the understanding of hydrophobicity, or the hydrophobic effect. The hydrophobic effect is primarily discussed in terms of partitioning of hydrocarbons between a hydrophobic environment and water as well as solubility of hydrocarbons in water. Micellization of surfactants is only briefly reviewed. It is emphasized that (i) the cause of the hydrophobic effect, e.g. the low solubility of a hydrocarbon in water, is to be found in the high internal energy of water resulting in a high energy to create a cavity in order to accommodate the hydrophobe, (ii) the “structuring” of water molecules around a hydrophobic compound increases the solubility of the hydrophobe. The “structuring” of water molecules around hydrophobic compounds is discussed in terms of recent spectroscopic findings. It is also emphasized that (iii) the lowering of entropy due to a structuring process must be accompanied by an enthalpy that is of the same order of magnitude as the TΔS for the process. Hence, there is an entropy–enthalpy compensation leading to a low free energy change for the structuring process. The assumption of a rapid decay of the entropy with temperature provides an explanation of the enthalpy–entropy compensation so often found in aqueous systems. It is also emphasized (iv) that the free energy obtained from partitioning, or solubility limits, needs to be corrected for molecular size differences between the solute and the solvent. The Flory–Huggins expression is a good first approximation for obtaining this correction. If the effect of different molecular sizes is not corrected for, this leads to erroneous conclusions regarding the thermodynamics of the hydrophobic effect. Finally, (v) micellization and adsorption of surfactants, as well as protein unfolding, are briefly discussed in terms of the hydrophobic effect.

  • 16. Li, H.
    et al.
    Somers, A. E.
    Howlett, P. C.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. School of Chemical Science and Engineering, KTH Royal Institute of Technology.
    Forsyth, M.
    Atkin, R.
    Addition of low concentrations of an ionic liquid to a base oil reduces friction over multiple length scales: A combined nano- and macrotribology investigation2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 9, p. 6541-6547Article in journal (Refereed)
    Abstract [en]

    The efficacy of ionic liquids (ILs) as lubricant additives to a model base oil has been probed at the nanoscale and macroscale as a function of IL concentration using the same materials. Silica surfaces lubricated with mixtures of the IL trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate and hexadecane are probed using atomic force microscopy (AFM) (nanoscale) and ball-on-disc tribometer (macroscale). At both length scales the pure IL is a much more effective lubricant than hexadecane. At the nanoscale, 2.0 mol% IL (and above) in hexadecane lubricates the silica as well as the pure IL due to the formation of a robust IL boundary layer that separates the sliding surfaces. At the macroscale the lubrication is highly load dependent; at low loads all the mixtures lubricate as effectively as the pure IL, whereas at higher loads rather high concentrations are required to provide IL like lubrication. Wear is also pronounced at high loads, for all cases except the pure IL, and a tribofilm is formed. Together, the nano- and macroscales results reveal that the IL is an effective lubricant additive - it reduces friction - in both the boundary regime at the nanoscale and mixed regime at the macroscale.

  • 17. Li, H.
    et al.
    Somers, A. E.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Department of Surface and Corrosion Science, School of Chemical Science and Engineering, KTH Royal Institute of Technology.
    Howlett, P. C.
    Atkin, R.
    Combined nano- and macrotribology studies of titania lubrication using the oil-ionic liquid mixtures2016In: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, Vol. 4, no 9, p. 5005-5012Article in journal (Refereed)
    Abstract [en]

    The lubrication of titania surfaces using a series of ionic liquid (IL)-hexadecane mixtures has been probed using nanoscale atomic force microscopy (AFM) and macroscale ball-on-disk tribometer measurements. The IL investigated is trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate, which is miscible with hexadecane in all proportions. At both length scales, the pure IL is a much more effective lubricant than pure hexadecane. At low loads, which are comparable to common industrial applications, the pure IL reduces the friction by 80% compared to pure hexadecane; while the IL-hexadecane mixtures lubricate the titania surface as effectively as the pure IL and wear decreases with increasing IL concentration. At high test loads the adsorbed ion boundary layer is displaced leading to surface contact and high friction, and wear is pronounced for all IL concentrations. Nonetheless, the IL performs better than a traditional zinc-dialkyl-dithophosphate (ZDDP) antiwear additive at the same concentration.

  • 18.
    Macakova, Lubica
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Aqueous lubrication by fractionated salivary proteins: Synergistic interaction of mucin polymer brush with low molecular weight macromolecules2015In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 89, p. 34-45Article in journal (Refereed)
  • 19.
    Macakova, Lubica
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Kjellin, Mikael
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Andersson, Martin
    LKs.
    Rapid assessment of glass etching/corrosion using the quartz crystal microbalance with dissipation monitoring, QCM-D2014In: Tenside Surfactants Detergents, ISSN 0932-3414, E-ISSN 2195-8564, Vol. 51, no 6, p. 484-490Article in journal (Refereed)
  • 20. Mahlapuu, Margit
    et al.
    Håkansson, Joakim
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Medicinteknik.
    Ringstad, Lovisa
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Björn, Camilla
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Medicinteknik. The Lundberg Laboratory for Diabetes Research, Department of Molecular and Clinical Medicine, The Sahlgrenska Academy at University of Gothenburg.
    Antimicrobial peptides: An emerging category of therapeutic agents2016In: Frontiers in Cellular and Infection Microbiology, Vol. 6, no DEC, article id 194Article in journal (Refereed)
    Abstract [en]

    Antimicrobial peptides (AMPs), also known as host defense peptides, are short and generally positively charged peptides found in a wide variety of life forms from microorganisms to humans. Most AMPs have the ability to kill microbial pathogens directly, whereas others act indirectly by modulating the host defense systems. Against a background of rapidly increasing resistance development to conventional antibiotics all over the world, efforts to bring AMPs into clinical use are accelerating. Several AMPs are currently being evaluated in clinical trials as novel anti-infectives, but also as new pharmacological agents to modulate the immune response, promote wound healing, and prevent post-surgical adhesions. In this review, we provide an overview of the biological role, classification, and mode of action of AMPs, discuss the opportunities and challenges to develop these peptides for clinical applications, and review the innovative formulation strategies for application of AMPs.

  • 21. Matougui, N.
    et al.
    Boge, Lukas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Groo, A. -C
    Umerska, A.
    Ringstad, Lovisa
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Bysell, Helena
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Saulnier, P.
    Lipid-based nanoformulations for peptide delivery2016In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 502, no 1-2, p. 80-97Article, review/survey (Refereed)
    Abstract [en]

    Nanoformulations have attracted a lot of attention because of their size-dependent properties. Among the array of nanoformulations, lipid nanoformulations (LNFs) have evoked increasing interest because of the advantages of their high degree of biocompatibility and versatility. The performance of lipid nanoformulations is greatly influenced by their composition and structure. Therapeutic peptides represent a growing share of the pharmaceutical market. However, the main challenge for their development into commercial products is their inherent physicochemical and biological instability. Important peptides such as insulin, calcitonin and cyclosporin A have been incorporated into LNFs. The association or encapsulation of peptides within lipid-based carriers has shown to protect the labile molecules against enzymatic degradation. This review describes strategies used for the formulation of peptides and some methods used for the assessment of association efficiency. The advantages and drawbacks of such carriers are also described.

  • 22.
    Mira, Isabel
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Andersson, Martin
    Foam forming revisited. Part II. Effect of surfactant on the properties of foam-formed paper products2014In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 29, no 4, p. 689-699Article in journal (Refereed)
  • 23.
    Mira, Isabel
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Andersson, Martin
    Boge, Lukas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Blute, Irena
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Carlsson, Gilbert
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Foam forming revisited Part I. Foaming behaviour of fibre-surfactant systems2014In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 29, no 4, p. 679-688Article in journal (Refereed)
  • 24.
    Mira, Isabel
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Swerin, Agne
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Ink-jettable paper-based sensor for charged macromolecules and surfactants2014In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 195, no May, p. 389-395Article in journal (Refereed)
  • 25.
    Nuzzo, Marine
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Fureby, Anna
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Surface Composition and Morphology of Particles Dried Individually and by Spray Drying2015In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 33, no 6, p. 757-767Article in journal (Refereed)
  • 26.
    Nuzzo, Marine
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Lund University, Food Technology, Engineering and Nutrition.
    Sloth, J.
    Bergenstahl, B.
    Millqvist-Fureby, Anna
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Phase segregation in individually dried particles composed of biopolymers2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 40, p. 10946-10954Article in journal (Refereed)
    Abstract [en]

    Mixing of two biopolymers can results in phase separation due to their thermodynamically incompatibility under certain conditions. This phenomenon was first reported when the solution was allowed to equilibrate, but it has later been observed also as a consequence of drying. The challenges of this study were to observe phase segregation by confocal Raman microscopy and LV-SEM on dried film, individually dried particles, and spray dried particles. The influence of the solid content and the phase ratio (composition) of a HPMC/maltodextrin mixture on the localization of the ingredients in the individually dried particles was investigated. We observed that phase segregation of HPMC and maltodextrin is induced by solvent evaporation in film drying, single particle drying, as well as spray drying. The phase ratio is an important parameter that influences the localization of the HPMC-enriched phase and maltodextrin-enriched phase, i.e., to the particle surface, to the core, or in a more or less bicontinuous pattern. The drying time, affected by the solids content, was found to control the level of advancement of the phase segregation.

  • 27. Nyström, L.
    et al.
    Nordström, R.
    Bramhill, J.
    Saunders, B. R.
    Álvarez-Asencio, R.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Department of Surface and Corrosion Science, School of Chemical Science and Engineering, KTH Royal Institute of Technology.
    Malmsten, M.
    Factors affecting peptide interactions with surface-bound microgels2016In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 17, no 2, p. 669-678Article in journal (Refereed)
    Abstract [en]

    Effects of electrostatics and peptide size on peptide interactions with surface-bound microgels were investigated with ellipsometry, confocal microscopy, and atomic force microscopy (AFM). Results show that binding of cationic poly-l-lysine (pLys) to anionic, covalently immobilized, poly(ethyl acrylate-co-methacrylic acid) microgels increased with increasing peptide net charge and microgel charge density. Furthermore, peptide release was facilitated by decreasing either microgel or peptide charge density. Analogously, increasing ionic strength facilitated peptide release for short peptides. As a result of peptide binding, the surface-bound microgels displayed pronounced deswelling and increased mechanical rigidity, the latter quantified by quantitative nanomechanical mapping. While short pLys was found to penetrate the entire microgel network and to result in almost complete charge neutralization, larger peptides were partially excluded from the microgel network, forming an outer peptide layer on the microgels. As a result of this difference, microgel flattening was more influenced by the lower Mw peptide than the higher. Peptide-induced deswelling was found to be lower for higher Mw pLys, the latter effect not observed for the corresponding microgels in the dispersed state. While the effects of electrostatics on peptide loading and release were similar to those observed for dispersed microgels, there were thus considerable effects of the underlying surface on peptide-induced microgel deswelling, which need to be considered in the design of surface-bound microgels as carriers of peptide loads, for example, in drug delivery or in functionalized biomaterials.

  • 28. Nyström, Lina
    et al.
    Álvarez-Asencio, Rubén
    Frenning, Göran
    Saunders, Brian R.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Department of Surface and Corrosion Science, School of Chemical Science and Engineering, KTH Royal Institute of Technology.
    Malmsten, Martin
    Electrostatic swelling transitions in surface-bound microgels2016In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, no 40, p. 27129-27139Article in journal (Refereed)
    Abstract [en]

    Herein, electrostatic swelling transitions of poly(ethyl acrylate-co-methacrylic acid) microgels covalently bound to silica surfaces are investigated. Confined at a solid surface, microgel swelling is anisotropically hindered and the structure is flattened to an extent dictated by pH and microgel composition. Microgel deformation under applied load is also shown to depend on microgel charge density, with the highest deformation observed at intermediate charge densities. Two modes of microgel deformation under load were observed, one elastic and one viscoelastic, related to polymer strand deformation and displacement of trapped water, respectively. Results on polymer strand dynamics reveal that the microgels are highly dynamic, as the number of strand-tip interaction points increases 4-fold during a 10 s contact time. Furthermore, finite element modeling captures these effects qualitatively and shows that stress propagation in the microgel network decays locally at the rim of contact with a solid interface or close to the tip probe. Taken together, the results demonstrate a delicate interplay between the surface and microgel which determines the structure and nanomechanical properties of the latter and needs to be controlled in applications of systems such as pH-responsive surface coatings in biomaterials.

  • 29.
    Oko, Asaf
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Medicinteknik.
    Claesson, Per M.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik. Department of Chemistry Surface and Corrosion Science, KTH Royal Institute of Technology.
    Niga, Petru
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Swerin, Agne
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Measurements and dimensional scaling of spontaneous imbibition of inkjet droplets on paper2016In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, no 1, p. 156-169Article in journal (Refereed)
    Abstract [en]

    We investigate theoretically and experimentally the spontaneous imbibition of water based inkjet formulations utilizing paper capillary rise and imbibition of inkjet drops. We approximate the paper structure to a two dimensional anisotropic porous material, and using Darcy's law as a base, we derive dimensionless groups that scale drop imbibition. This derivation is based on a previous dimensional scaling of drop imbibition on thick isotropic porous material. We apply this scaling to a paper substrate by measuring the average drop imbibition rate, and perform paper capillary rise experiments to obtain the average system parameters required for the scaling. The results suggest that this approach is a valuable tool to predict drop imbibition rates on paper. We then continue and perform the same sets of experiments on a different paper with similar structure that is surface treated (surface sized) with CaCl2 salt, an additive that is known to improve print quality. We find that due to rapid aggregation of the colorant ink by the CaCl2, the imbibition rate is slowed down in the capillary rise experiments, i.e., on much larger scales compared to a single inkjet drop. However, the presence of CaCl2 has only minor effect over the average imbibition rates of single drops. Imbibition rates on the CaCl2 surface sized paper did not give adequate scaling as a result of the fact that the aggregation was not included the theoretical assumptions behind the scaling.

  • 30. Persson, Karin
    et al.
    Blute, Irena
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Mira, Isabel
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Creation of well-defined particle stabilized oil-in-water nanoemulsions2014In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 459, p. 48-57Article in journal (Refereed)
  • 31. Pradhan, S.
    et al.
    Hedberg, J.
    Blomberg, Eva
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Department of Chemistry, Surface and Corrosion Science, KTH Royal Institute of Technology.
    Wold, S.
    Odnevall Wallinder, I.
    Effect of sonication on particle dispersion, administered dose and metal release of non-functionalized, non-inert metal nanoparticles2016In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 18, no 9, article id 285Article in journal (Refereed)
    Abstract [en]

    In this study, we elucidate the effect of different sonication techniques to efficiently prepare particle dispersions from selected non-functionalized NPs (Cu, Al, Mn, ZnO), and corresponding consequences on the particle dose, surface charge and release of metals. Probe sonication was shown to be the preferred method for dispersing non-inert, non-functionalized metal NPs (Cu, Mn, Al). However, rapid sedimentation during sonication resulted in differences between the real and the administered doses in the order of 30–80 % when sonicating in 1 and 2.56 g/L NP stock solutions. After sonication, extensive agglomeration of the metal NPs resulted in rapid sedimentation of all particles. DLVO calculations supported these findings, showing the strong van der Waals forces of the metal NPs to result in significant NP agglomeration. Metal release from the metal NPs was slightly increased by increased sonication. The addition of a stabilizing agent (bovine serum albumin) had an accelerating effect on the release of metals in sonicated solutions. For Cu and Mn NPs, the extent of particle dissolution increased from <1.6 to ~5 % after sonication for 15 min. A prolonged sonication time (3–15 min) had negligible effects on the zeta potential of the studied NPs. In all, it is shown that it is of utmost importance to carefully investigate how sonication influences the physico-chemical properties of dispersed metal NPs. This should be considered in nanotoxicology investigations of metal NPs. Graphical Abstract: [Figure not available: see fulltext.]

  • 32.
    Puig von Friesen, Marc
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Energi och Bioekonomi, Klimatisering och installationsteknik.
    Arinder, Pernilla
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Microbiology.
    Lundin, Maria
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Yarahmadi, Nazdaneh
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Bygg och Mekanik, Rörcentrum.
    Kjellin, Mikael
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Kurkinen, Eva-Lotta
    Byggnadsfysik och innemiljö (ETi ).
    Thörnblom, Kristian
    Göteborg (BMg).
    Säkerställa vattenkvalitet vid 45˚C med avseende på Legionella: En förstudie för innovationsupphandling2014Report (Refereed)
  • 33. Salminen, K.
    et al.
    Lappalainen, T.
    Kinnunen-Raudaskoski, K.
    Andersson, M.
    Carlsson, Gilbert
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Polymer och fiber.
    Mira, Isabel
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Foam forming-the effects of surfactant type on characteristics of fiber-foam suspension and properties of formed fiber network2014In: Paper Conference and Trade Show, PaperCon 2014, TAPPI Press, 2014, p. 758-765Conference paper (Refereed)
    Abstract [en]

    The properties and behavior of pure aqueous foams have been quite extensively studied. On the other hand, very little is known about the chemical interactions between foaming agents and paper/board making raw materials in aqueous fiber-foam suspensions. The objective of this examination was to increase the understanding of basic mechanisms affecting fiber-foam suspension. In particular, gaining understanding of the chemical interactions between foaming agents and paper/board making raw materials was of great interest. The foaming behavior of pulp formulations in the presence of three anionic and four non-ionic foaming aids was tested with a tailor-made foaming test environment. Foaming aids for testing were chosen based on their reported good foaming properties, environmental safety, and availability as bulk chemicals, as well as their insensitivity to changes in temperature and pH within limits relevant to the foam forming process. Foam formed hand sheets with different furnish recipes were made and tested to evaluate the effect of the three selected foaming agents (selected based on their foaming characteristics) on the formation and retention processes, the technical properties of the hand sheets, and the performance of other chemicals used in paper/board manufacturing in the presence of the foaming aids. Additionally, the potential of utilizing the selected foaming aids in practical foam forming of paper or board was verified in a small-scale pilot trial. The results obtained in these laboratory and pilot-scale studies showed that the type and amount of foaming aids used have significant effects on foam properties, filler retention, sizing, dewatering, bulk, and mechanical properties of the fiber network. In fact, the selection of the foaming aid and its interaction with other wet end additives seems to be one of the key factors affecting the processability and quality of foam formed products.

  • 34.
    Skedung, Lisa
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Model for contact between finger and sinusoidal plane to evaluate adhesion and deformation component of friction2014In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, no Dec, p. in pre-Article in journal (Refereed)
  • 35.
    Skedung, Lisa
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Buraczewska-Norin, I.
    Dawood, N.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Department of Surface and Corrosion Science, School of Chemical Science and Engineering, KTH Royal Institute of Technology.
    Ringstad, Lovisa
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Tactile friction of topical formulations2016In: Skin research and technology, ISSN 0909-752X, E-ISSN 1600-0846, Vol. 22, no 1, p. 46-54Article in journal (Refereed)
    Abstract [en]

    Background: The tactile perception is essential for all types of topical formulations (cosmetic, pharmaceutical, medical device) and the possibility to predict the sensorial response by using instrumental methods instead of sensory testing would save time and cost at an early stage product development. Here, we report on an instrumental evaluation method using tactile friction measurements to estimate perceptual attributes of topical formulations. Methods: Friction was measured between an index finger and an artificial skin substrate after application of formulations using a force sensor. Both model formulations of liquid crystalline phase structures with significantly different tactile properties, as well as commercial pharmaceutical moisturizing creams being more tactile-similar, were investigated. Friction coefficients were calculated as the ratio of the friction force to the applied load. The structures of the model formulations and phase transitions as a result of water evaporation were identified using optical microscopy. Results: The friction device could distinguish friction coefficients between the phase structures, as well as the commercial creams after spreading and absorption into the substrate. In addition, phase transitions resulting in alterations in the feel of the formulations could be detected. A correlation was established between skin hydration and friction coefficient, where hydrated skin gave rise to higher friction. Also a link between skin smoothening and finger friction was established for the commercial moisturizing creams, although further investigations are needed to analyse this and correlations with other sensorial attributes in more detail. Conclusion: The present investigation shows that tactile friction measurements have potential as an alternative or complement in the evaluation of perception of topical formulations.

  • 36.
    Skedung, Lisa
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Ringstad, Lovisa
    Rutland, Mark
    Tactile friction of topical formulations2013In: 5th World Tribology Congress, WTC 2013, 2013, , p. 2249-2251Conference paper (Refereed)
  • 37.
    Skedung, Lisa
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Rutland, Mark
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Feeling small: Exploring the tactile perception limits2013In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, p. 2617-Article in journal (Refereed)
  • 38.
    Skedung, Lisa
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Rutland, Mark
    Tribology, texture and touch2013In: 5th World Tribology Congress, WTC 2013, 2013, , p. 2270-2273Conference paper (Refereed)
  • 39. Svagan, A. J.
    et al.
    Benjamins, Jan-Willem
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Al-Ansari, Z.
    Shalom, D. B.
    Müllertz, A.
    Wågberg, L.
    Löbmann, K.
    Solid cellulose nanofiber based foams – Towards facile design of sustained drug delivery systems2016In: Journal of Controlled Release, ISSN 0168-3659, E-ISSN 1873-4995, Vol. 244, p. 74-82Article in journal (Refereed)
    Abstract [en]

    Control of drug action through formulation is a vital and very challenging topic within pharmaceutical sciences. Cellulose nanofibers (CNF) are an excipient candidate in pharmaceutical formulations that could be used to easily optimize drug delivery rates. CNF has interesting physico-chemical properties that, when combined with surfactants, can be used to create very stable air bubbles and dry foams. Utilizing this inherent property, it is possible to modify the release kinetics of the model drug riboflavin in a facile way. Wet foams were prepared using cationic CNF and a pharmaceutically acceptable surfactant (lauric acid sodium salt). The drug was suspended in the wet-stable foams followed by a drying step to obtain dry foams. Flexible cellular solid materials of different thicknesses, shapes and drug loadings (up to 50 wt%) could successfully be prepared. The drug was released from the solid foams in a diffusion-controlled, sustained manner due to the presence of intact air bubbles which imparted a tortuous diffusion path. The diffusion coefficient was assessed using Franz cells and shown to be more than one order of magnitude smaller for the cellular solids compared to the bubble-free films in the wet state. By changing the dimensions of dry foams while keeping drug load and total weight constant, the drug release kinetics could be modified, e.g. a rectangular box-shaped foam of 8 mm thickness released only 59% of the drug after 24 h whereas a thinner foam sample (0.6 mm) released 78% of its drug content within 8 h. In comparison, the drug release from films (0.009 mm, with the same total mass and an outer surface area comparable to the thinner foam) was much faster, amounting to 72% of the drug within 1 h. The entrapped air bubbles in the foam also induced positive buoyancy, which is interesting from the perspective of gastroretentive drug-delivery.

  • 40. Wakeham, D.
    et al.
    Crivoi, D. G.
    Medina, F.
    Segarra, A. M.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Department of Surface and Corrosion Science, School of Chemical Science and Engineering, KTH Royal Institute of Technology.
    In-situ study of substrate - catalyst interactions in a Juliá-Colonna epoxidation using quartz crystal microbalance with dissipation2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 469, p. 263-268Article in journal (Refereed)
    Abstract [en]

    Quartz crystal microbalance with dissipation (QCM-D) analysis of the hexa-l-Leucine (PLL)-catalyzed epoxidation of chalcone gives in-situ experimental evidences which demonstrate that the reaction proceeds mainly via the formation of a PLL-bound hydroperoxide complex followed by the reversible addition of chalcone. The observations offer an alternative rationalization for the viability of the preferred catalytic pathway.

  • 41. Wang, X.
    et al.
    Herting, G.
    Odnevall Wallinder, I.
    Blomberg, Eva
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Department of Chemistry, Surface and Corrosion Science, KTH Royal Institute of Technology.
    Adsorption of bovine serum albumin on silver surfaces enhances the release of silver at pH neutral conditions2015In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 28, p. 18524-18534Article in journal (Refereed)
    Abstract [en]

    Metallic biomaterials are widely used to replace and/or restore the function of damaged bodily parts. The use of silver as antibacterial coatings onto implants has recently gained large interest in medical applications. The extent of silver that can be released into different biological fluids from such coatings is, except for the surface characteristics of the coating, governed by parameters such as protein characteristics, adsorbed layer properties, formation of silver-protein complexes as well as concentrations of proteins in the solution. This study aims to relate the structure of adsorbed net negatively charged bovine serum albumin (BSA), which is the most abundant protein in serum, to the release of silver from metallic silver surfaces in order to elucidate if the net charge of the protein has any effect of the silver release. Simultaneous adsorption measurements were performed in real time on the very same surface using combined ellipsometry and quartz crystal microbalance with dissipation monitoring (QCM-D) measurements to provide a more comprehensive understanding on adsorption kinetics and layer structures. The amount of released silver into solution was measured by means of graphite furnace atomic absorption spectroscopy (GF-AAS). The structure of the adsorbed BSA layer largely influenced the amount of released silver, an enhancement that increased with BSA concentration. These observations are in complete contrast to the effect of net positively charged lysozyme (LSZ) adsorbed on silver, previously studied by the authors, for which a complete surface coverage suppressed the possibility for silver release. The underlying mechanisms behind the enhanced release of silver in the presence of BSA were mainly attributed to surface complexation between BSA and silver followed by an enhanced exchange rate of these surface complexes with BSA molecules in the solution, which in turn increase the amount of released silver in solution.

  • 42. Wieland, D. C. F.
    et al.
    Degen, P.
    Zander, T.
    Gayer, S.
    Raj, A.
    An, J.
    Dédinaité, Andra A
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. KTH Royal Institute of Technology, School of Chemical Sciences and Engineering, Department of Chemistry, Surface and Corrosion Science.
    Claesson, Per M.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik. Department of Chemistry Surface and Corrosion Science, KTH Royal Institute of Technology.
    Willumeit-Römer, R.
    Structure of DPPC-hyaluronan interfacial layers-effects of molecular weight and ion composition2016In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 12, no 3, p. 729-740Article in journal (Refereed)
    Abstract [en]

    Hyaluronan and phospholipids play an important role in lubrication in articular joints and provide in combination with glycoproteins exceptionally low friction coefficients. We have investigated the structural organization of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) Langmuir layers at the solution-air interface at different length scales with respect to the adsorption of hyaluronan (HA). This allows us to assemble a comprehensive picture of the adsorption and the resulting structures, and how they are affected by the molecular weight of HA and the presence of calcium ions. Brewster angle microscopy and grazing incident diffraction were used to determine the lateral structure at the micro- and macro scale. The data reveals an influence of HA on both the macro and micro structure of the DPPC Langmuir layer, and that the strength of this effect increases with decreasing molecular weight of HA and in presence of calcium ions. Furthermore, from X-ray reflectivity measurements we conclude that HA adsorbs to the hydrophilic part of DPPC, but data also suggest that two types of interfacial structures are formed at the interface. We argue that hydrophobic forces and electrostatic interactions play important rules for the association between DPPC and HA. Surface pressure area isotherms were used to determine the influence of HA on the phase behavior of DPPC while electrophoretic mobility measurements were used to gain insight into the binding of calcium ions to DPPC vesicles and hyaluronan.

  • 43. Wieland, D. C. F.
    et al.
    Garamus, V. M.
    Zander, T.
    Krywka, C.
    Wang, M.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor. Department of Chemistry, Surface and Corrosion Science, KTH Royal Institute of Technology.
    Dédinaité, Andra A
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. KTH Royal Institute of Technology, School of Chemical Sciences and Engineering, Department of Chemistry, Surface and Corrosion Science.
    Claesson, Per M.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik. Department of Chemistry Surface and Corrosion Science, KTH Royal Institute of Technology.
    Willumeit-Römera, R.
    Studying solutions at high shear rates: A dedicated microfluidics setup2016In: Journal of Synchrotron Radiation, ISSN 0909-0495, E-ISSN 1600-5775, Vol. 23, no 2, p. 480-486Article in journal (Refereed)
    Abstract [en]

    The development of a dedicated small-angle X-ray scattering setup for the investigation of complex fluids at different controlled shear conditions is reported. The setup utilizes a microfluidics chip with a narrowing channel. As a consequence, a shear gradient is generated within the channel and the effect of shear rate on structure and interactions is mapped spatially. In a first experiment small-angle X-ray scattering is utilized to investigate highly concentrated protein solutions up to a shear rate of 300000 s-1. These data demonstrate that equilibrium clusters of lysozyme are destabilized at high shear rates.

  • 44. Zander, Thomas
    et al.
    Wieland, Florian
    Raj, Akanksha
    Wang, Min
    Nowak, Benedikt
    Krywka, Christina
    Dédinaité, Andra A
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. KTH Royal Institute of Technology, School of Chemical Sciences and Engineering, Department of Chemistry, Surface and Corrosion Science.
    Claesson, Per M.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik. Department of Chemistry Surface and Corrosion Science, KTH Royal Institute of Technology.
    Garamus, Vasil M.
    Schreyer, Andreas
    Willumeit-Römer, Regine
    The influence of hyaluronan on the structure of a DPPC-bilayer under high pressures2016In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 142, p. 230–238-Article in journal (Refereed)
    Abstract [en]

    The superior lubrication properties of synovial joints have inspired many studies aiming at uncovering the molecular mechanisms which give rise to low friction and wear. However, the mechanisms are not fully understood yet, and, in particular, it has not been elucidated how the biolubricants present at the interface of cartilage respond to high pressures, which arise during high loads of joints. In this study we utilize a simple model system composed of two biomolecules that have been implied as being important for joint lubrication. It consists of a solid supported dipalmitoylphosphatidylcholin (DPPC) bilayer, which was formed via vesicles fusion on a flat Si wafer, and the anionic polysaccharide hyaluronan (HA). We first characterized the structure of the HA layer that adsorbed to the DPPC bilayers at ambient pressure and different temperatures using X-ray reflectivity (XRR) measurements. Next, XRR was utilized to evaluate the response of the system to high hydrostatic pressures, up to 2 kbar (200 MPa), at three different temperatures. By means of fluorescence microscopy images the distribution of DPPC and HA on the surface was visualized. Our data suggest that HA adsorbs to the headgroup region that is oriented towards the water side of the supported bilayer. Phase transitions of the bilayer in response to temperature and pressure changes were also observed in presence and absence of HA. Our results reveal a higher stability against high hydrostatic pressures for DPPC/HA composite layers compared to that of the DPPC bilayer in absence of HA.

  • 45. Álvarez-Asencio, R.
    et al.
    Wallqvist, Viveca
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Kjellin, Mikael
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Life Science. Department of Surface and Corrosion Science, School of Chemical Science and Engineering, KTH Royal Institute of Technology.
    Camacho, A.
    Nordgren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Luengo, G. S.
    Nanomechanical properties of human skin and introduction of a novel hair indenter2016In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 54, p. 185-193Article in journal (Refereed)
    Abstract [en]

    The mechanical resistance of the stratum corneum, the outermost layer of skin, to deformation has been evaluated at different length scales using Atomic Force Microscopy. Nanomechanical surface mapping was first conducted using a sharp silicon tip and revealed that Young’s modulus of the stratum corneum varied over the surface with a mean value of about 0.4 GPa. Force indentation measurements showed permanent deformation of the skin surface only at high applied loads (above 4 μN). The latter effect was further demonstrated using nanomechanical imaging in which the obtained depth profiles clearly illustrate the effects of increased normal force on the elastic/plastic surface deformation. Force measurements utilizing the single hair fiber probe supported the nanoindentation results of the stratum corneum being highly elastic at the nanoscale, but revealed that the lateral scale of the deformation determines the effective elastic modulus.This result resolves the fact that the reported values in the literature vary greatly and will help to understand the biophysics of the interaction of razor cut hairs that curl back during growth and interact with the skin.

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