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  • 1.
    Berglin, Mattias
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Gradients in surface nanotopography used to study platelet adhesion and activation2013In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 110, no 1, p. 261-269Article in journal (Refereed)
  • 2. Bergstrand, A.
    et al.
    Svanberg, C.
    Langton, Maud
    SIK – Institutet för livsmedel och bioteknik.
    Nyden, M.
    Aggregation behavior and size of lipopolysaccharide from Escherichia coli O55:B52006In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 53, no 1, p. 42261-Article in journal (Refereed)
    Abstract [en]

    Dynamic light scattering, steady-state fluorescence, NMR diffusometry and cryo-TEM have been used to gain more insight into the aggregation behaviour of LPS from Escherichia coli O55:B5. Knowledge of this behaviour of the amphiphilic LPS molecule is in many cases of importance for the design of experiments and interpretation of results when using LPS in solution. The aim of this work was to study the aggregation and determine the aggregate size of E. coli O55:B5. The mean hydrodynamic radius of the LPS aggregates was determined by NMR diffusometry and dynamic light scattering to 14 and 26 nm, respectively. The cryo-TEM technique revealed predominately spherical aggregates of 9-19 nm. We wish to report 10 ?g/ml as the aggregation start for LPS E. coli O55:B5 in PBS buffer, pH 7.2. We suggest that the aggregation is a continuous process that starts at 10 ?g/ml and proceeds up to 300 ?g/ml. © 2006.

  • 3.
    Blomberg, Eva
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Correlation between surface physicochemical properties and the release of iron from stainless steel AISI 304 in biological media2014In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 122, no Oct, p. 216-222Article in journal (Refereed)
  • 4. Bogdanovic, G
    et al.
    Meurk, A
    Rutland, MW
    YKI – Ytkemiska institutet.
    Tip friction – torsional spring constant determination2000In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 19, p. 397-405Article in journal (Refereed)
    Abstract [en]

    A non-destructive technique is presented for verifying torsional spring constants used in lateral force microscopy. Various calibrations of the microscope are required and these are detailed. The technique produces reasonable values which tend to be larger than those predicted >from considerations of the cantilever dimensions. The differences are discussed in terms of length corrections and particularly the uncertainty in the thickness of the cantilevers, which has an enormous effect on the values obtained through a priori calculations. Methods for inferring the thickness are discussed. Further, artefacts in conventional force measurements related to the experiments performed here are discussed.

  • 5. Campos, J
    et al.
    Eskilsson, K
    YKI – Ytkemiska institutet.
    Nylander, T
    Svendsen, A
    On the interaction between adsorbed layers of monoolein and the lipase action on the formed layers2002In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 26, p. 172-182Article in journal (Refereed)
    Abstract [en]

    We used the Surface Force Apparatus (SFA) and ellipsometry techniques to study the interaction forces and the adsorption behavior of monoolein (MO), respectively. MO was adsorbed from water to a hydrophobised mica or silica surface. In addition the effect of added lipase, Thermomyces (Humicula) lanuginosa lipase (TLL), to an adsorbed layer of MO was investigated. The force versus distance curves between two MO covered surfaces feature a strong repulsive interaction beneath 400 Å. The range of the repulsive force decreases, however, with the number of approaches. No adhesion was observed, provided that the surfaces were not taken to hydrophobic contact. The surface separation at MO¯MO contact was determined to about 55 Å. This means a layer thickness of about 27 Å, which is comparable to the thickness (25 Å) determined by ellipsometry. The repulsive force may arise from compression of a cubic phase of MO. This phase are suggested to form between the surfaces when they approach close contact due to capillary induced phase separation (CIPS) from the saturated MO solution. The repulsive force changes significantly with time after addition of TLL (concentration of about 1?10-8 M). In contrast to the force curves recorded before adding TLL, the surfaces do not seem to be completely covered with MO as we always observed an attractive force (inward jump) of similar range as was observed between pure OTE surfaces. Ellipsometry measurement of TLL action on MO covered hydrophobic surface reveals a significant and sharp decrease of the amounts adsorbed. Furthermore, the rate of decrease and reduction in adsorbed amount increased with TLL concentration.

  • 6. Cozzolino, C.A
    et al.
    Nilsson, F.
    Iotti, M.
    Sacchi, B.
    Piga, A.
    Exploiting the nano-sized features of microfibrillated cellulose (MFC) for the development of controlled-release packaging2013In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 110Article in journal (Refereed)
  • 7. Eriksson, C
    et al.
    Blomberg, E
    YKI – Ytkemiska institutet.
    Claesson, P
    YKI – Ytkemiska institutet.
    Nygren, H
    Reactions of two hydrophilic surfaces with detergents, protein and whole human blood1997In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 9, p. 67-79Article in journal (Refereed)
    Abstract [en]

    The surface chemistry of moscovite mica and hydrophilic glass was characterized by ESCA. The adsorption of detergents and lysozyme was measured by surface force methods, ellipsometry or ESCA. The results show that the peotein has a higher affinity to the mica surface. A biological characterisation of the surfaces was performed by exposure to whole blood, followed by detection of surface-adsorbed plasma proteins and cellular antigens by immunofluorescence. The brighteness of the fluorescence was measured by computer-aided image analysis. The results show that the hydrophilic glass was the most efficient activator of serine protease cascade enzymes. Platelets were activated at both surfaces, but were shown to leave the glass surface with time. The glass surface was more inflammatogenic than the mica surface as determined by the CD 11b - integrin expression of PMN-cells. The results indicate that the nonself recognition of the surfaces is an array of subreactions, the kinetics of which determine the outcome of the blood- material contact.

  • 8.
    Gerdes, S
    et al.
    YKI – Ytkemiska institutet.
    Ström, G
    YKI – Ytkemiska institutet.
    Spreading of oil droplets on silicon oxide surfaces with parallel v-shaped channels1996In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 116, p. 135-144Article in journal (Refereed)
    Abstract [en]

    The spreading of silicone oil and paraffin oil has been studied on two energetically and chemically different smooth surfaces (gold and polystyrene). It was found that for these surfaces neither the surface tension nor the surface free energy influenced the spreading behaviour of the oils. The data for the two different liquids can be transposed onto a master curve when the product of velocity and viscosity is plotted versus the dynamic contact angle. Spreading of paraffin oil droplets where also studied on a set of silicone oxide surfaces containing parallel v-shaped surface channels at various widths and spacings. It was found that the sharp edges of the channel walls strongly affected spreading and that droplet shape was distorted from the usual circular shape displayed on a smooth surface. Ån elongated droplet was formed with the contact line following a channel edge and with the short sides having a semi-circular shape. Traverse spreading was very slow and decreased as the spacing was decreased. Increased channel size and decreased spacing produced an increase in spreading velocity in the direction of the channels.

  • 9. Haghshenas, N
    et al.
    Smith, P
    YKI – Ytkemiska institutet.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    The exchange rate between dissolved tripalmitin and tripalmitin crystals2001In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 21, p. 239-243Article in journal (Refereed)
    Abstract [en]

    The focus of this paper is on understanding the exchange between dissolved fats and fat crystals in dispersions by quantifying the rate of the exchange between the fats in solution and in crystals. In the studies reported here, tripalmitin (PPP) was used as model fat. The dispersions contained PPP crystals and dissolved radio-labelled PPP (14C-PPP, used as the probe) in a medium chain triglyceride oil (MCT). The exchange process between the dissolved 14C-PPP and unlabelled PPP crystals was followed using a radio-detector. The effect of the crystal concentration on the exchange rate was studied. The results suggested that the rate of the exchange is dependent upon both the dissolution of the surface of the crystals and also diffusion and crystallisation of the dissolved compounds.

  • 10. 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.

  • 11. Landström, K
    et al.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Alsins, J
    Almgren, M
    A fluorescence method for quantitative measurements of specific protein at powder surfaces1999In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 12, p. 429-440Article in journal (Refereed)
    Abstract [en]

    A new method using fluorescence labeled proteins was developed to determine the quantitative amount of specific protein at the powder surface. The method is based on steady-state fluorescence measurements of pyrene labeled proteins with oxygen gas phase quenching at the powder surface. The surface load of protein was measured for spray-dried dextran powders containing bovine serum albumin (BSA). The results show a patchwise surface load of about 1.3 mg/m2 at a concentration of 0.33 % (dry weight) BSA in the powder. The patchwise surface load stays constant with increased BSA concentration in the powder.

  • 12. Lindh, L
    et al.
    Glantz, P-O
    Carlstedt, I
    Wickström, C
    Arnebrant, T
    YKI – Ytkemiska institutet.
    Adsorption of MUC5B and the role of mucins in early salivary film formation2002In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 25, p. 139-146Article in journal (Refereed)
    Abstract [en]

    Salivary mucins are known to play important roles in the formation of oral salivary films. The aims of the present study were to investigate the behaviour of salivary mucins at solid surfaces with different wettabilities, as well as the influence of electrolyte on the adsorption behaviour. A pure preparation of human salivary MUC5B was used together with a commercial one of bovine submaxillary mucin (BSM). Amounts adsorbed from freshly prepared solutions onto hydrophilic and hydrophobic surfaces versus time were measured in situ by ellipsometry. At low concentrations, larger amounts were adsorbed onto hydrophobic than onto hydrophilic silica indicating a higher affinity for the former surfaces. Furthermore, on hydrophilic surfaces adsorbed amounts of MUC5B and BSM show good agreement at low concentrations (<0.10 mg ml-1). However, at higher concentrations MUC5B adsorbed to a lower extent than BSM. At hydrophobic surfaces, isotherm shapes were similar for the two preparations, but the amounts were shifted to higher values for MUC5B. Finally, the presence of electrolyte increased adsorption and the increase was more pronounced on hydrophilic surfaces. The increased adsorption at a higher ionic strength indicates a more compact structure of the mucin due to electrostatic screening and the fact that the effect was more pronounced on the hydrophilic surfaces points to a higher relative importance of electrostatic interactions in this case. We conclude that the two mucins investigated behave in a qualitatively similar manner and show the highest affinity for hydrophobic surfaces.

  • 13. Lundin, Maria
    et al.
    Elofsson, Ulla M
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Blomberg, Eva
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Adsorption of lysozyme, beta-casein and their layer-by-layer formation on hydrophilic surfaces: Effect of ionic strength2010In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 77, no 1, p. 1-11Article in journal (Refereed)
    Abstract [en]

    The adsorbed amount and layer structure of lysozyme, _x0002_-casein and mixed layers of the two proteins were studied on hydrophilic silica and quartz surfaces using the following techniques: ellipsometry, quartz crystal microbalance with dissipation monitoring (QCM-D) and total internal reflection fluorescence (TIRF). Particular emphasis was put on the effect of solution ionic strength on the layer formation. Both lysozyme and _x0002_-casein showed a higher affinity for the silica surface when adsorbed from a solution of low ionic strength even though _x0002_-casein and silica are negatively charged at the pH used. No _x0002_-casein remained adsorbed after rinsing with a 150mMbuffer solution. The adsorbed amount of lysozyme on silica exceeded a monolayer coverage irrespective of the solution conditions and displayed a rigid structure. _x0002_-Casein forms more than a single layer on pre-adsorbed lysozyme; an inner flat layer and an outer layer with an extended structure, which largely desorbs on rinsing. The build-up through sequential adsorption of lysozyme and _x0002_-casein is favoured at intermediate and high ionic strength. The total adsorbed amount increased slightly with each deposition cycle and the mixed lysozyme/_x0002_-casein layers contain higher amounts of protein compared to those of pure lysozyme or _x0002_-casein. Sequential adsorption gives rise to a proteinaceous layer consisting of both lysozyme and _x0002_-casein. The protein layers are probably highly interpenetrated with no clear separation between them.

  • 14.
    Macakova, Lubica
    et al.
    YKI – Ytkemiska institutet.
    Yakubov, Gleb E
    Plunkett, Mark A
    Stokes, Jason R
    Influence of ionic strength changes on the structure of pre-adsorbed salivary films. A response of a natural multi-component layer2010In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 77, no 1, p. 31-39Article in journal (Refereed)
    Abstract [en]

    Salivary films coating oral surfaces are critically important for oral health. This study focuses on determining the underlying nature of this adsorbed film and how it responds to departures from physiological conditions due to changes in ionic strength. Under physiological conditions, it is found that pre-adsorbed in vitro salivary film on hydrophobic surfaces is present as a highly hydrated viscoelastic layer. We follow the evolution of this film in terms of its effective thickness, hydration and viscoelastic properties, as well as adsorbed mass of proteins, using complementary surface characterisation methods: a Surface Plasmon Resonance (SPR) and a Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D). Our results support a heterogeneous model for the structure of the salivary film with an inner dense anchoring layer and an outer highly extended hydrated layer. Further swelling of the film was observed upon decreasing the salt concentration down to 1 mM NaCl. However, upon exposure to deionised water, a collapse of the film occurs that was associated with the loss of water contained within the adsorbed layer. We suggest that the collapse in deionised water is driven by an onset of electrostatic attraction between different parts of the multi-component salivary film. It is anticipated that such changes could also occur when the oral cavity is exposed to food, beverage, oral care and pharmaceutical formulations where drastic changes to the structural integrity of the film is likely to have implications on oral health, sensory perception and product performance.

  • 15.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Ellipsometry studies of fibronectin adsorption1995In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 3, p. 371-381Article in journal (Refereed)
    Abstract [en]

    The adsorption of fibronectin at a series of different surfaces was investigated with in situ ellipsometry. For silica and methylated silica, the adsorbed amount (G), the adsorbed layer thickness (del) and the mean adsorbed layer refractive index (nf) were obtained by a procedure involving studies of the bare substrate at two different ambient refractive indices, as well as four-zone averaging. It was found that the adsorbed amount of fibronectin was the same (1.9±0.1 mg/m2) at silica and methylated silica. However, the adsorbed layers formed at methylated silica were more extended and had a lower average protein concentration than those formed at silica. Furthermore, at both silica and methylated silica, an increasing adsorbed amount is achieved both by a denser packing of the fibronectin molecules and by a growth of the adsorbed layer normal to the surface. Furthermore, the adsorption of fibronectin at lipid surfaces was investigated. It was found that the adsorption of fibronectin to phosphatidic acid was quite significant (2.2±0.2 mg/m2), while that at phosphatidylcholine, phosphatidylinositol and phosphatidylserine was much smaller (all 0.1±0.05 mg/m2). These results are correlated to findings on the adsorption of fibrinogen at these surface, as well as on the opsonization of lipid-stabilized colloidal particles.

  • 16.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Ellipsometry studies of the effect of surface hydrophobicity on protein adsorption1995In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 3, p. 297-308Article in journal (Refereed)
    Abstract [en]

    The adsorption of some model proteins, human serum albumin (HSA), IgG, fibrinogen and lysozyme at silica surfaces was investigated with in situ ellipsometry and compared to previous results obtained for methylated silica surfaces. The adsorbed amount (G), the adsorbed layer thickness (del) and the mean adsorbed layer refractive index (nf) were obtained by a procedure involving studies of the bare substrate at two different ambient refractive indices, as well as four-zone averaging. The surface hydrophobicity strongly influenced the adsorption properties of all the proteins studied. For HSA, IgG and fibrinogen, the adsorbed amount was significantly lower at the hydrophilic surface than at the hydrophobic one, whereas the reverse was found for lysozyme. For fibrinogen, the adsorbed layer thickness at silica was smaller than that at methylated silica, whereas the adsorbed layer was more concentrated. For IgG, on the other hand, end-on adsorption was observed at both silica and methylated silica. For lysozyme, side-on adsorption in a dense monolayer was observed at silica, whereas at methylated silica, the adsorption occurs in 2-3 rather dilute molecular layers. Furthermore, the build-up of the adsorbed layers was studied. For fibrinogen, qualitatively the same behaviour was observed for silica and methylated silica, i e, as the adsorbed amount increases, both del and nf increase initially, while closer to adsorption saturation, nf levels off. However, at a given G, del was lower and nf higher at silica than at methylated silica. A similar finding was obtained for lysozyme. These findings are discussed in terms of the adsorbed layer structure and formation.

  • 17.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Johansson, J-Å
    Burns, NL
    Yasuda, H
    Protein adsorption at n-butane plasma polymer surfaces1996In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 6, p. 191-199Article in journal (Refereed)
    Abstract [en]

    The adsorption of human serum albumin (HSA) and fibrinogen at n-butane plasma polymer surfaces prepared by low temperature plasma polymerization at different energy inputs have been investigated with in situ ellipsometry. Within experimental uncertainty, the adsorption of both fibrinogen and HSA is constant over the power range used for the preparation of the n-butane surfaces and corresponds to that found for other hydrophobic surfaces at similar conditions. Furthermore, novel copolymer surfaces of n-butane and nitrogen at different ratios were prepared and investigated. Increasing the nitrogen content in the gas mixture during deposition resulted in an increased density of interfacial amine groups, as evidenced by an increased wettability, an increased interfacial nitrogen content, and an increased surface positive charge. This, in turn, was found to result in an increased fibrinogen adsorption, but in a weak decrease in the HSA adsorption.

  • 18.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Larsson, A
    Immobilization of trypsin on porous glycidyl methacrylate beads; effects of polymer hydrophilization2000In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 18, p. 277-284Article in journal (Refereed)
    Abstract [en]

    The immobilization of trypsin at porous glycidyl methacrylate (GMA-GDMA) beads was investigated. In particular, the effects of surface modification of the beads through hydrophilic polymers on the amount protein immobilized and on the extent of retained activity after immobilization were adressed. Furthermore, immobilization at unmodified and hydrophilized beads from aqueous solution was compared to that from a water-in-oil microemulsion. It was found that the amount trypsin immobilized at the unmodified GMA-GDMA beads was significantly higher than that at hydrophilized GMA-GDMA beads. However, also the extent of specific activity loss after immobilization was larger for the unmodified than for the hydrophilized beads. Despite the latter, however, the total activity displayed by the hydrophilized beads was comparable to the unmodified beads at best. On the other hand, by peforming the immobilization from the microemulsion a high immobilization yield can be reached even for the hydrophilized beads, which also results in a higher degree of retained activity in the latter case than obtained for immobilization at the unmodified beads. Using this approach therefore resulted in the highest total activity of the trypsin-activated GMA-GDMA beads.

  • 19.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Lassen, B
    Competitive protein adsorption at phospholipid surfaces1995In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 4, p. 173-184Article in journal (Refereed)
    Abstract [en]

    The interfacial exchange processes between human serum albumin (HSA) and fibrinogen at different surfaces was investigated with in situ ellipsometry and TIRF. With ellipsometry, it was found that the total adsorbed amount at silica on addition of fibrinogen after preadsorption of HSA was quite similar to that obtained without HSA preadsorption. From TIRF, it is concluded that the preadsorbed HSA is displaced, although not completely, on addition of fibrinogen. On the other hand, preadsorbed HSA effectively blocked further adsorption of fibrinogen and IgG at hydrophobic surfaces such as methylated silica. Furthermore, the competitive adsorption of HSA and fibrinogen at two phospholipid surfaces, i e, phosphatidylcholine (PC) and phosphatidic acid (PA), was investigated. It was found that at PA, fibrinogen adsorbs extensively even after preadsorption of HSA. This, however, is achieved with essentially no displacement of the preadsorbed HSA. For PC, finally, the fibrinogen adsorption is much lower than that of HSA, and fibrinogen is able neither to coadsorb with HSA nor to displace the preadsorbed protein.

  • 20.
    Malmsten, M
    et al.
    YKI – Ytkemiska institutet.
    Ljusegren, I
    Carlstedt, I
    Ellipsometry studies of the mucoadhesion of cellulose derivatives1994In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 2, p. 463-470Article in journal (Refereed)
    Abstract [en]

    The mucoadhesion of three different cellulose derivatives, ethyl(hydroxyethyl)cellulose (EHEC), hydrophobically modified hydroxyethyl cellulose (h-HEC) and a cationic cellulose derivative (amino cellulose), was investigated with in situ ellipsometry. In the measurements, gastric mucin from rat was first adsorbed onto hydrophobized silica, which provided good anchorage for the mucin layer and allowed a large amount of mucin to be adsorbed. Significant mucoadhesion was obtained for all three cellulose derivatives, indicating that either overall solvency effects, electrostatic interactions or hydrophobic groups may be used to obtain mucoadhesion in cellulose systems. Of the polymers used, EHEC showed the greatest tendency for adsorption, which may indicate that the first approach is preferable for obtaining efficient mucoadhesion. The addition of SDS was found to counteract mucoadhesion of EHEC.

  • 21.
    Millqvist-Fureby, A
    YKI – Ytkemiska institutet.
    Characterisation of spray-dried emulsions with mixed fat phases2003In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 31, p. 65-79Article in journal (Refereed)
    Abstract [en]

    Fat encapsulation in spray-dried protein-stabilised emulsions is known to depend on the choice of protein, the emulsion droplet size, and the melting point of the fat. However, the fat encapsulation may also depend on the fat crystal habit. Fats may crystallise in three different α, ß' and ß, of which the ß-form is thermodynamically stable. The α-form is obtained in rapidly cooled fats, and it can then transform into the ß'-form during storage, and this crystal form is finally transformed into the ß-form. In order to investigate the effect of different fat phases on the spray-dried emulsions, two solid fats were studied: fully hardened rapeseed oil (ß-stable) and fully hardened palm oil (ß'-stable). The solid fats were used on their own or in mixtures with rapeseed oil, in order to provide fat phases with different properties. The emulsion composition was chosen as to mimic the composition of whole milk, i.e. 40% lactose, 30% sodium caseinate and 30% fat on a dry weight basis. The dried powders were stored under dry conditions at 4 or 37 °C in order to investigate the changes in the fat crystals and surface composition of the powders with time. The surface composition was analysed using electron spectroscopy for chemical analysis. Evaluation of the data showed that surface coverage of fat varied depending on the composition of the fat phase. The ratio of lactose to protein remained constant, which implies that the fat was present as `islands' on a surface composed of lactose and protein. The hardened palm oil crystallised initially in the α- or ß'-form (depending on the ratio of hardened fat to oil), and during storage, the crystal form gradually changed into the ß'-form. In powders containing hardened rapeseed oil only the stable ß-form was found, even in fresh samples. The surface coverage of fat was reduced after storage, whereas the ratio of lactose to protein at the surface remained unchanged. The emulsion droplet size in emulsions prepared at a low homogenisation pressure was considerably increased after spray-drying and reconstitution, whilst the emulsion droplet size was well preserved in emulsions prepared at high homogenisation pressure

  • 22.
    Millqvist-Fureby, A
    et al.
    YKI – Ytkemiska institutet.
    Elofsson, U
    YKI – Ytkemiska institutet.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Surface composition of spray-dried milk protein-stabilised emulsions in relation to pre-heat treatment of proteins2001In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 21, p. 47-58Article in journal (Refereed)
    Abstract [en]

    Several important technical properties of spray-dried food powders depend on particle-liquid interactions (e.g. wettability, dispersability) and particle-particle interactions (e.g. flowability). It can be assumed that the chemical composition of the surface layer of the particles to a large extent determine these properties. The present study has been aimed to investigate the relation between the surface composition of spray-dried milk protein-stabilised emulsions and pre-heat treatment of the proteins. Solutions of WPC were heat-treated at low (60-90°C) and high (140°C) temperature and the degree of denaturation was determined, prior to the preparation of emulsions with rapeseed oil. The surface composition of the dry powders were established by using ESCA (electron spectroscopy of chemical analysis).The emulsions were characterised by droplet size distribution before spray drying and after dissolution of the powders. Also free fat extractions and estimations of wettability (dissolution rates) were performed. The powder surface coverage of protein decreased with increasing degree of protein denaturation before the emulsification, whereas the emulsion droplet size increased both before spray drying and after reconstitution of powders. The free fat extraction as well as the dissolution rate, whereof the latter decreased with increasing surface fat coverage, correlated well with the fat coverage of the powder surface.

  • 23. Nylander, T
    et al.
    Tiberg, F
    YKI – Ytkemiska institutet.
    Wetting of β-casein layers adsorbed at the solid-aqueous interface1999In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 15, p. 253-261Article in journal (Refereed)
    Abstract [en]

    The wetting by water of adsorbed layer of β-casein on hydrobised silica and pure (hydrophilic) silica surface was investigated by dynamic contact angle measurements based on the Wilhelmy plate principle. The results are discussed in relation to adsorption studies on similar surfaces using in situ ellipsometry. The results show that adsorbing β-casein to a hydrophobic surface lead to a significant decrease of the contact angle in particular in terms of the receding contact angle, for which a decrease of about 70 degrees was observed. This indicates a strong shielding of the hydrophobic surface by hydrophilic β-casein groups. Adding a specific enzyme, endoproteinase Asp-N, which previously have been proposed to remove a large fraction of these segments, results in a significantly decreased wettability of the solid surface. The layer is now more hydrophobic and the hysterises is much smaller. The receding contact angle after the proteolysis is roughly 70°. The results are consistent with the hypothesis that β-casein adsorb at hydrophobic surface to form a monolayer with the hydrophobic part of the protein anchored at the surface, leaving the hydrophilic segments dangling into the solution. On the hydrophilic surface, less dramatic effects are observed in terms of changes of the wettability. The surface is still quite hydrophilic both after adsorbing β-casein and exposing the layer to endoporteinase Asp-N. These results confirm previously discussed differences in the structure of β-casein layers on the hydrophobic and hydrophilic surface.

  • 24. Olsson, J
    et al.
    Carlén, A
    Burns, NL
    Holmberg, K
    YKI – Ytkemiska institutet.
    Modified pellicle formation and reduced in vitro bacterial adherence after surface treatment with different siloxane polymers1995In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 5, p. 161-169Article in journal (Refereed)
    Abstract [en]

    Formation of salivary pellicles is a prerequisite of bacterial colonization on the tooth and the aim of this study has been to further the understanding of the role of surface properties in formation of the salivary pellicle and subsequent adhesion of oral bacteria. Surface modification as a means of interfering with pellicle and plaque formation has been investigated. Five different silicone-containing compounds were used for the surface treatments: polydimethylsiloxane containing aminoalkyl groups (I), polydimethylsiloxane containing partially neutralized aminoalkyl groups (II), ethyl silicate (III), potassium methyl siliconate (IV) and sodium silicate (V). Studies of water wetting, surface charge, oral bacterial adherence, pellicle and plaque formation were performed on glass slides, hydroxyapatite beads or teeth coated by the test compounds. No correlation was found between contact angle and surface charge, and evidently hydrophobicity, as expressed by water wetting, is not necessarily an indicaton of a low surface concentration of polar groups. All compounds reduced bacterial adherence after saliva contact, compound IV by around 90%. Different patterns were seen in the adsorption of pellicle proteins on the different polysiloxanes. Clinical experiments, however, did not reveal any significant differences in plaque formation.

  • 25. Skagerlind, P
    et al.
    Jansson, M
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Hult, K
    Binding of Rhizomucor miehei lipase to emulsion interfaces and its interference with surfactants1995In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 4, p. 129-135Article in journal (Refereed)
    Abstract [en]

    Interactions between Rhizomucor miehei lipase and emulsion droplets were studied in oil-in-water emulsions. The emulsions were stabilised by either the cationic surfactant didodecyldimethylammonium bromide, the anionic surfactant sodium bis (2-ethylhexyl) sulfosuccinate or the non-ionic surfactant, 1-(2-ethylhexyl)-3-(2-ethylbutyl)-2-hexaethylene glycerol ether. By measuring the mobility of emulsion droplets it was shown that the lipase bound to droplets stabilized by the nonionic surfactant, but not to those stabilized by the negatively charged surfactants. It was experimentally impossible to show any adsorption of the lipase to the emulsion droplet surfaces consisting of the non-ionic surfactant. From Langmuir measurements it was decuced that the lipase adsorbed to positively but not negatively charged surfaces. Only a small change of the break point of the isotherm was observed in the non-ionic system. Eicosanoic acid disappeared from the air/water interface at pH4, when Rhizomucor miehei lipase was dissolved in teh subsolution. The lipase-catalyzed hydrolysis of the oil-soluble model substrate, o-nitrophenyl palmitate, was studied in emulsions stabilized by the different surfactants. The highest reaction rate was observed in systems with the non-ionic surfactant and also with the cationic surfactant, while in the anionic system almost no reaction was observed. In all three tests, i.e. the mobility of emulsion droplets, Langmuir measurements and enzymatic activity measurements, an increased salt concentration from 1μM to 1 mM sodium phosphate decreased the affinity of the lipase to the surfaces stabilized by the cationic surfactant. With a lipase-stabilized oil-in-water emulsion, displacement of the lipase from the emulsion droplet surface occurred with the cationic surfactant, but not with the anionic surfactant. Again with the non-ionic system, it was not possible to show any displacement of the lipase since the mobility value for the lipase system was almost the same as for the non-iopnic system. From each set of experiment it could be concluded independently that the lipase from Rhizomucor miehei prefers positively charged surfaces over negatively charged surfaces.

  • 26. Sonesson, AW
    et al.
    Callisen, TH
    Brismar, H
    Elofsson, UM
    YKI – Ytkemiska institutet.
    A comparison between dual polarization interferometry (DPI) and surface plasmon resonance (SPR) for protein adsorption studies2007In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 54, p. 236-240Article in journal (Refereed)
    Abstract [en]

    This work was performed with the aim of comparing protein adsorption results obtained from the recently developed dual polarization interferometry (DPI) with the well-established surface plasmon resonance (SPR) technique. Both techniques use an evanescent field as the sensing element but completely different methods to calculate the adsorbed mass. As a test system we used adsorption of the lipase from Thermomyces lanuginosus (TLL) on C18 surfaces. The adsorbed amount calculated with both techniques is in good agreement, with both adsorption isotherms saturating at 1.30–1.35 mg/m2 at TLL concentrations of 1000nM and above. Therefore, this supports the use of both SPR and DPI as tools for studying protein adsorption, which is very important when comparing adsorption data obtained from the use different techniques. Due to the spot sensing in SPR, this technique is recommended for initial kinetic studies, whereas DPI is more accurate when the refractive index and thickness of the adsorbed layer is of more interest.

  • 27. Sonesson, AW
    et al.
    Callisen, TH
    Elofsson, UM
    YKI – Ytkemiska institutet.
    Brismar, H
    Adsorption and activity of Thermomyces lanuginosus lipase on hydrophobic and hydrophilic surfaces measured with dual polarization interferometry (DPI) and confocal microscopy2008In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 61, p. 208-215Article in journal (Refereed)
    Abstract [en]

    The adsorption and activity of Thermomyces lanuginosus lipase (TLL) was measured with dual polarization interferometry (DPI) and confocal microscopy at a hydrophilic and hydrophobic surface. In the adsorption isotherms, it was evident that TLL both had higher affinity for the hydrophobic surface and adsorbed to a higher adsorbed amount (1.90 mg/m2) compared to the hydrophilic surface (1.40–1.50 mg/m2). The thickness of the adsorbed layer was constant (not, vert, similar3.5 nm) on both surfaces at an adsorbed amount >1.0 mg/m2, but decreased on the hydrophilic surface at lower surface coverage, which might be explained by partially unfolding of the TLL structure. However, a linear dependence of the refractive index of the adsorbed layer on adsorbed amount of TLL on C18 surfaces indicated that the structure of TLL was similar at low and high surface coverage. The activity of adsorbed TLL was measured towards carboxyfluorescein diacetate (CFDA) in solution, which upon lipase activity formed a fluorescent product. The surface fluorescence intensity increase was measured in a confocal microscope as a function of time after lipase adsorption. It was evident that TLL was more active on the hydrophilic surface, which suggested that a larger fraction of adsorbed TLL molecules were oriented with the active site facing the solution compared to the hydrophobic surface. Moreover, most of the activity remained when the TLL surface coverage decreased. Earlier reports on TLL surface mobility on the same surfaces have found that the lateral diffusion was highest on hydrophilic surfaces and at low surface coverage of TLL. Hence, a high lateral mobility might lead to a longer exposure time of the active site towards solution, thereby increasing the activity against a water-soluble substrate.

  • 28. Van Alstine, JM
    et al.
    Malmsten, M
    YKI – Ytkemiska institutet.
    Long, MM
    Johnson, VK
    DeLucas, LJ
    Polymer coatings for improved protein crystal growth1999In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 14, p. 197-211Article in journal (Refereed)
    Abstract [en]

    The ability to grow quality protein crystals is necessary to analyze protein structure by X-ray diffraction and related techniques. As such it plays a key role in enzymology, structure-based drug design, molecular biology, and other biomedical areas. It is also required for macromolecule purification by crystallization. Protein crystal growth (PCG) may be negatively influenced by various factors related to nonspecific adsorption and adherence at growth chamber surfaces. Such factors include nucleation and growth of flawed crystals at chamber walls, or wall growth blockage of optical monitoring paths. Surface localized poly(ethylene glycol) (PEG) and other neutral, hydrophilic polymers are known to significantly reduce nonspecific adsorption of biological macromolecules and particles. Preliminary studies, involving various PCG methods (temperature induction, vapor diffusion), apparatii (test tubes, cuvettes, and specialized PCG hardware), growth chamber materials (glass, polystyrene, polysulfone), chamber volumes (0.1-10 mi) and protein samples (lysozyme, thaumatin, insulin) indicate the potential of PEG coatings to significantly reduce problems related to adsorption in PCG. The results, which match the ability of such coatings to reduce protein adsorption as evaluated by both ellipsometry and enzyme linked immunoassay, are discussed in relation to colloidal stabilization theory and properties of PEG coated surfaces.

  • 29. 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.

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