| 1. |
- Campos, J, et al.
(author)
-
On the interaction between adsorbed layers of monoolein and the lipase action on the formed layers
- 2002
-
In: Colloids and Surfaces B: Biointerfaces. - 1873-4367 .- 0927-7765. ; 26:1-2, s. 172-182
-
Journal article (peer-reviewed)abstract
- 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 A. 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 Angstrom This means a layer thickness of about 27 Angstrom, which is comparable to the thickness (25 Angstrom) 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 x 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. (C) 2002 Elsevier Science B.V. All rights. reserved.
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| 2. |
- Lindh, Liselott, et al.
(author)
-
Adsorption of MUC5B and the role of mucins in early salivary film formation
- 2002
-
In: Colloids and Surfaces B: Biointerfaces. - : Elsevier. - 1873-4367 .- 0927-7765. ; 25:2, s. 139-146
-
Journal article (peer-reviewed)abstract
- 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 MUM 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.
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| 3. |
- Wannerberger, Kristin, et al.
(author)
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Adsorption from lipase-surfactant solutions onto methylated silica surfaces
- 1996
-
In: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 1873-4367 .- 0927-7765. ; 6:1, s. 27-36
-
Journal article (peer-reviewed)abstract
- In situ ellipsometry was used to study the adsorption/desorption of highly purified lipase from Humicola lanuginosa in mixtures with surfactants, at the solid/liquid interface. The effect of the surfactant was studied both when it was allowed to adsorb in mixture with lipase and when added after lipase adsorption. Silica surfaces, totally or partially methylated, were used and the surfactants were SDS (anionic), C12E5 and a commercial alcohol ethoxylate (AE) (both nonionic). The experiments were carried out so as to simulate a laundry process and the pH throughout the study was kept at 9 by means of Tris-HCl buffer.From the results it was shown that the lipase did not adsorb until the diluted, that is during the rinsing period. This was found for all the lipase-surfactant mixtures in the study. However, the amount of lipase adsorbed was larger after rinsing in mixture with SDS, compared with C12E5. The results from addition of surfactant after lipase adsorption indicated that the lipase was replaced by surfactant. This was found for SDS and C12E5 at both the hydrophobic surface and the surface with intermediate hydrophobicity.
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| 4. |
- Benesch, Johan, et al.
(author)
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Quantification of adsorbed human serum albumin at solid interfaces : A comparison between radioimmunoassay (RIA) and simple null ellipsometry
- 2000
-
In: Colloids and Surfaces B. - 0927-7765 .- 1873-4367. ; 18:2, s. 71-81
-
Journal article (peer-reviewed)abstract
- Radioimmunoassay (RIA) and null ellipsometry are two common methods to quantify adsorbed proteins. However, the accuracy of null ellipsometry with a constant protein refractive index (n=1.465, k=0) at ?=632.8 nm has this far not been explored. The present study compared the methods, and the degree of agreement between the simplified single wavelength null ellipsometry and RIA to quantify adsorbed proteins was explored on different surfaces. The quantification methods agreed well when Angstrom smooth hydrophilic or hydrophobic silicon surfaces, and freshly radio-labelled proteins were used. Some discrepancies were noted when either rough surface or stored and aged labelled proteins were used. The differences decreased when the aged protein solution was equilibrated with freshly dissolved proteins at room temperature (RT) for a few hours prior to the surface incubations. Significant differences were also noted between the methods when albumin was adsorbed at it's iso-electric point (pH 4.8). Copyright (C) 2000 Elsevier Science B.V.
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| 5. |
- Bogdanovic, G., et al.
(author)
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Tip friction - torsional spring constant determination
- 2000
-
In: Colloids and Surfaces B. - 0927-7765 .- 1873-4367. ; 19:4, s. 397-405
-
Journal article (peer-reviewed)abstract
- 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.
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| 6. |
- Evertsson, H., et al.
(author)
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NMR self diffusion measurements of the monooleoylglycerol/poly ethylene glycol/water L-3 phase
- 2002
-
In: Colloids and Surfaces B. - 0927-7765 .- 1873-4367. ; 26:02-jan, s. 21-29
-
Journal article (peer-reviewed)abstract
- The monooleoylglycerol (GMO)/poly ethylene oxide (PEG)/water sponge (L-3) phase has been investigated by pulsed-gradient spin-echo NMR self-diffusion. The data allow the L-3 phase to be modeled as a bicontinuous system with respect to the lipid and water domains. It is proposed by using the interconnected rod model that the solvent PEG mainly distributes to the water domain, but has a higher weight fraction partition to the lipid head groups of the local GMO bilayer than water. The data is put in relation to earlier self-diffusion measurements on the binary GMO/water cubic phase, as well as earlier conductivity and X-ray diffraction measurements on the very same L-3 phase.
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| 7. |
- Hook, F.F, et al.
(author)
-
A comparative study of protein adsorption on titanium oxide surfaces using in situ ellipsometry, optical waveguide lightmode spectroscopy, and quartz crystal microbalance/dissipation
- 2002
-
In: Colloids and Surfaces B. - 0927-7765 .- 1873-4367. ; 24:2, s. 155-170
-
Journal article (peer-reviewed)abstract
- The adsorption kinetics of three model proteins - human serum albumin, fibrinogen and hemoglobin - has been measured and compared using three different experimental techniques: optical waveguide lightmode spectroscopy (OWLS), ellipsometry (ELM) and quartz crystal microbalance (QCM-D). The studies were complemented by also monitoring the corresponding antibody interactions with the pre-adsorbed protein layer. All measurements were performed with identically prepared titanium oxide coated substrates. All three techniques are suitable to follow in-situ kinetics of protein-surface and protein-antibody interactions, and provide quantitative values of the adsorbed adlayer mass. The results have, however, different physical contents. The optical techniques OWLS and ELM provide in most cases consistent and comparable results, which can be straightforwardly converted to adsorbed protein molar ('dry') mass. QCM-D, on the other hand, produces measured values that are generally higher in terms of mass. This, in turn, provides valuable, complementary information in two respects: (i) the mass calculated from the resonance frequency shift includes both protein mass and water that binds or hydrodynamically couples to the protein adlayer, and (ii) analysis of the energy dissipation in the adlayer and its magnitude in relation to the frequency shift (c.f. adsorbed mass) provides insight about the mechanical/structural properties such as viscoelasticity. © 2002 Elsevier Science B.V. All rights reserved.
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| 8. |
- Lestelius, Magnus, et al.
(author)
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Order/disorder gradients of n-alkanethiols on gold
- 1999
-
In: Colloids and Surfaces B. - : Elsevier. - 0927-7765 .- 1873-4367. ; 15:1, s. 57-70
-
Journal article (peer-reviewed)abstract
- This paper explores the interfacial properties of one-dimensional molecular gradients of alkanethiols (HS-(CH2)(n)- X) on gold. The kinetics and thermodynamics of monolayer formation are important issues for these types of mixed molecular assemblies. The influence of chain length difference on the contact angles with hexadecane (HD), theta(a) and theta(r), and the hysteresis, has been studied by employing alkanethiols HS-(CH2)(n)-CH3, with n = 9, 11, 13, 15 and 17, in the preparation of the self-assembled monolayers (SAM) gradients. The contact angles with hexadecane, at the very extreme ends of the gradients, show characteristic values of a highly ordered CH3-like assembly: theta(a) = 45-50 degrees. In the middle of the gradients theta(a) drops noticeably and exhibits values representative for CH2-like polymethylenes, theta(a) = 20-30 degrees, indicating a substantial disordering of the protruding chains of the longer component in the gradient assembly. As expected, the exposure of CH2-groups to the probing liquid increases with increasing differential chain length of the two n-alkanethiol used, in this case eight methylene units. However, the contact angles always display a non-zero value which means that even at a chain length difference of eight methylene units there is a substantial exposure of methyl (CH3) groups to the probing liquid. With infrared reflection-absorption spectroscopy (IRAS) we have monitored the structural behavior of the polymethylene chains along the gradient. We find complementary evidence for disordered chains in the gradient region, and the IRAS results correlate well with the contact angle measurements. (C) 1999 Elsevier Science B.V. All rights reserved.
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| 9. |
- Petoral, Rodrigo Jr, 1975-, et al.
(author)
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Arg–Cys and Arg–cysteamine adsorbed on gold and the G-protein–adsorbate interaction
- 2002
-
In: Colloids and Surfaces B. - 0927-7765 .- 1873-4367. ; 25:4, s. 335-346
-
Journal article (peer-reviewed)abstract
- The dipeptide, Arg–Cys, and the related molecule, Arg–cysteamine, are adsorbed to gold surfaces and the monolayers are characterized. Chemical binding and electronic structure of the monolayers are obtained by X-ray photoelectron spectroscopy (XPS). Strong molecular binding of the adsorbates to gold surface through the sulfur atom is attained. Orientation of the adsorbates on gold is studied using infrared reflection absorption spectroscopy (IRAS). Arg–Cys is interpreted to be adsorbed on gold in a compact configuration. The Arg–cysteamine molecule is adsorbed on gold with the main molecular axis perpendicular to the surface. Interaction of G-protein with the adsorbates was studied using the surface plasmon resonance (SPR) technique. It is believed that arginine has a major role in G-protein recognition since the G-protein-coupled receptor (GPCR) α2A has an arginine-rich region in the G-protein-binding part of the third intracellular loop.
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| 10. |
- Sharma, P.K., et al.
(author)
-
Adhesion of Paenibacillus polymyxa on chalcopyrite and pyrite : Surface thermodynamics and extended DLVO theory
- 2003
-
In: Colloids and Surfaces B. - 0927-7765 .- 1873-4367. ; 29:1, s. 21-38
-
Journal article (peer-reviewed)abstract
- The adhesion behaviour of Paenibacillus polymyxa bacteria on pyrite and chalcopyrite is examined by the surface thermodynamics and the extended DLVO theory approaches. In addition, the bacteria are adapted to pyrite and chalcopyrite minerals, and the adhesion behaviour of these bacteria is also investigated. The significance of acid-base interactions in adhesion is assessed. The essential parameters needed for the calculations of interaction energy between bacteria and mineral are experimentally determined. The results illustrate that the bacterial surfaces are more energetic than the mineral surfaces and the bacteria acquired acid-base surface energy component during their adaptation to mineral. The extended DLVO approach is found to be more effective in predicting the adhesion behaviour than the expectations from thermodynamic approach. The thermodynamic approach yields no bacterial adhesion on minerals and this discrepancy is the result of inadequate description of electrostatic interactions. The adhesion predictions by the DLVO approach are able to partially explain the bioflotation results of pyrite and chalcopyrite. Extended DLVO shows that on account of high bacterial surface energy, their aggregation is not feasible. But due to the hydrophobicity of pyrite and chalcopyrite, their aggregation is possible.
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| 11. |
- Tengvall, Pentti, et al.
(author)
-
Ellipsometric in vitro studies on the activation of complement by human immunoglobulins M and G after adsorption to methylated silicon
- 2001
-
In: Colloids and Surfaces B. - 0927-7765 .- 1873-4367. ; 20:1, s. 51-62
-
Journal article (peer-reviewed)abstract
- Human serum immunoglobulin M (IgM) or human immunoglobulin G (IgG) were adsorbed to dichlorodimethyl silane (DDS) treated silicon. Subsequently, the model surfaces were incubated in normal-, complement factor 1q (C1q)-complement factor B or complement factor 2 (C2)-depleted human sera at 37°C for up to 1.5 h. The serum deposition and binding of selected polyclonal complement antibodies into this layer were then quantified by null ellipsometry. Both types of precoated surfaces bound large amounts of anti-complement factor 3c (anti-C3c), anti-properdin and anti-C3d, after incubation in normal serum. In contrast to IgG coated surfaces, IgM coated surfaces bound no anti-C1q after the serum incubations and no anti-C3c deposition lag time was observed after incubations in EGTA serum. Upon immersions of IgM coated surfaces in the different sera, a rapid complement activation via a C1q factor B, and Ca2+-independent, but C2 dependent pathway, was indicated. When IgM was instead immobilized to APTES/glutaraldehyde surfaces, anti-C3c deposition was lower after incubations in EGTA than normal serum. The results suggest that, under the present experimental conditions, human IgM and IgG activate the complement system differently. (C) 2001 Elsevier Science B.V.
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| 12. |
- Tengvall, Pentti, et al.
(author)
-
Preparation of multilayer plasma protein films on silicon by EDC/NHS coupling chemistry
- 2003
-
In: Colloids and Surfaces B. - 0927-7765 .- 1873-4367. ; 28:4, s. 261-272
-
Journal article (peer-reviewed)abstract
- Crosslinked multilayer protein films were prepared from fibrinogen, albumin, IgG, a combination of fibrinogen and catalase, and blood plasma on silicon by ethyl-dimethyl-aminopropylcarbodiimide and N-hydroxy-succinimide coupling chemistry. The 4-70 nm thick films were placed in blood plasma and the additional protein deposition measured by null ellipsometry after 5 or 60 min of incubation. The activation of the complement system and intrinsic pathway of coagulation were indicated through the subsequent binding of anti-C3c, anti-C3d, anti-properdin and anti-HMWK on top of the surface bound blood plasma. The proportion of Annexin V, Propidium Iodide and 4,6-diamidino-2-phenylindole positive cells, and the secretion of tumor necrosis factor a (TNF-a) and interleukin-10 (IL-10) were analysed in a monocyte culture. The results show that well known protein coupling techniques can be used for the preparation of protein layers with well controlled thickness. The layers possess low contact activation of blood plasma and induce different release of TNF-a and IL-10 in monocyte cultures. © 2002 Elsevier Science B.V. All rights reserved.
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| 13. |
- Acet, Ömür, et al.
(author)
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Inhibition of bacterial adhesion by epigallocatechin gallate attached polymeric membranes
- 2023
-
In: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 221
-
Journal article (peer-reviewed)abstract
- Microbial adhesion and formation of biofilms cause a serious problem in several areas including but not limited to food spoilage, industrial corrosion and nosocomial infections. These microbial biofilms pose a serious threat to human health since microbial communities in the biofilm matrix are protected with exopolymeric substances and difficult to eradicate with antibiotics. Hence, the prevention of microbial adhesion followed by biofilm formation is one of the promising strategies to prevent these consequences. The attachment of antimicrobial agents, coatings of nanomaterials and synthesis of hybrid materials are widely used approach to develop surfaces having potential to hinder bacterial adhesion and biofilm formation. In this study, epigallocatechin gallate (EGCG) is attached on p(HEMA-co-GMA) membranes to prevent the bacterial colonization. The attachment of EGCG to membranes was proved by Fourier-transform infrared spectroscopy (FT-IR). The synthesized membrane showed porous structure (SEM), and desirable swelling degree, which are ideal when it comes to the application in biotechnology and biomedicine. Furthermore, EGCG attached membrane showed significant potential to prevent the microbial colonization on the surface. The obtained results suggest that EGCG attached polymer could be used as an alternative approach to prevent the microbial colonization on the biomedical surfaces, food processing equipment as well as development of microbial resistant food packaging systems.
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| 14. |
- Aggarwal, N., et al.
(author)
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Study on multilayer structures prepared from heparin and semi-synthetic cellulose sulfates as polyanions and their influence on cellular response
- 2014
-
In: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 116, s. 93-103
-
Journal article (peer-reviewed)abstract
- Multilayer coatings of polycationic chitosan paired with polyanionic semi-synthetic cellulose sulfates or heparin were prepared by the layer-by-layer method. Two different cellulose sulfates (CS) with high (CS2.6) and intermediate (CS1.6) sulfation degree were prepared by sulfation of cellulose. Multilayers were fabricated at pH 4 and the resulting films were characterized by several methods. The multilayer 'optical' mass, measured by surface plasmon resonance, showed little differences in the total mass adsorbed irrespective of which polyanion was used. In contrast, 'acoustic' mass, calculated from quartz crystal micro balance with dissipation monitoring, showed the lowest mass and dissipation values for CS2.6 (highest sulfation degree) multilayers indicating formation of stiffer layers compared to heparin and CS1.6 layers which led to higher mass and dissipation values. Water contact angle and zeta potential measurements indicated formation of more distinct layers with using heparin as polyanion, while use of CS1.6 and CS2.6 resulted into more fuzzy intermingled multilayers. CS1.6 multilayers significantly supported adhesion and growth of C2C12 cells where as only few cells attached and started to spread initially on CS2.6 layers but favoured long term cell growth. Contrastingly cells adhered and grew poorly on to the layers of heparin. This present study shows that cellulose sulfates are attractive candidates for multilayer formation as potential substratum for controlled cell adhesion. Since a peculiar interaction of cellulose sulfates with growth factors was found during previous studies, immobilization of cellulose sulfate in multilayer systems might be of great interest for tissue engineering applications.
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| 15. |
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| 16. |
- Al-Soubaihi, Rola, et al.
(author)
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Silica and carbon decorated silica nanosheet impact on primary human immune cells
- 2018
-
In: Colloids and Surfaces B. - : Elsevier B.V.. - 0927-7765 .- 1873-4367. ; 172, s. 779-789
-
Journal article (peer-reviewed)abstract
- Silica nanosheets (SiO 2 NS) are considered to be a promising material in clinical practice for diagnosis and therapy applications. However, an appropriate surface functionalization is essential to guarantee high biocompatibility and molecule loading ability. Although SiO 2 NS are chemically stable, its effects on immune systems are still being explored. In this work, we successfully synthesized a novel 2D multilayer SiO 2 NS and SiO 2 NS coated with carbon (C/SiO 2 NS), and evaluated their impact on human Peripheral Blood Mononuclear Cells (PBMCs) and some immune cell subpopulations. We demonstrated that the immune response is strongly dependent on the surface functionalities of the SiO 2 NS. Ex vivo experiments showed an increase in biocompatibility of C/SiO 2 NS compared to SiO 2 NS, resulting in a lowering of hemoglobin release together with a reduction in cellular toxicity and cellular activation. However, none of them are directly involved in the activation of the acute inflammation process with a consequent release of pro-inflammatory cytokines. The obtained results provide an important direction towards the biomedical applications of silica nanosheets, rendering them an attractive material for the development of future immunological therapies.
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| 17. |
- Allerbo, Oskar, 1985, et al.
(author)
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Simulations of lipid vesicle rupture induced by an adjacent supported lipid bilayer patch
- 2011
-
In: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 82:2, s. 632-636
-
Journal article (peer-reviewed)abstract
- Using a simple phenomenological model of a lipid bilayer and a surface, simulations were performed to study the bilayer-induced vesicle rupture probability as a vesicle adsorbs adjacently to a bilayer patch already adsorbed on the surface. The vesicle rupture probability was studied as a function of temperature, vesicle size, and surface-bilayer interaction strength. From the simulation data, estimates of the apparent activation energy for bilayer-induced vesicle rupture were calculated, both for different vesicle sizes and for different surface-bilayer interaction strengths.
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| 18. |
- Allerbo, Oskar, et al.
(author)
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Simulations of Lipid Vesicle Rupture Induced by an Adjacent Supported Lipid Bilayer Patch
- 2011
-
In: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 82, s. 632-636
-
Journal article (peer-reviewed)abstract
- Using a simple phenomenological model of a lipid bilayer and a surface, simulations were performed to study the bilayer-induced vesicle rupture probability as a vesicle adsorbs adjacently to a bilayer patch already adsorbed on the surface. The vesicle rupture probability was studied as a function of temperature, vesicle size, and surface-bilayer interaction strength. From the simulation data, estimates of the apparent activation energy for bilayer-induced vesicle rupture were calculated, both for different vesicle sizes and for different surface-bilayer interaction strengths.
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| 19. |
- Andersson, Martin, 1974, et al.
(author)
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Vesicle and bilayer formation of diphytanoylphosphatidylcholine (DPhPC) and diphytanoylphosphatidylethanolamine (DPhPE) mixtures and their bilayers' electrical stability
- 2011
-
In: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 82:2, s. 550-561
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Journal article (peer-reviewed)abstract
- Lipid bilayers are of interest in applications where a cell membrane mimicking environment is desired. The performance of the lipid bilayer is largely dependent on the physical and chemical properties of the component lipids. Lipid bilayers consisting of phytanoyl lipids have proven to be appropriate choices since they exhibit high mechanical and chemical stability. In addition, such bilayers have high electrical resistances. Two different phytanoyl lipids, 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) and 1,2-diphytanoyl-sn-glycero-3-phosphoethanolamine(DPhPE), and various combinations of the two have been investigated with respect to their behavior in aqueous solutions, their interactions with solid surfaces, and their electrical stability. Dynamic light scattering, nuclear magnetic resonance diffusion, and cryogenic transmission electron microscopy measurements showed that pure DPhPC as well as mixtures of DPhPC and DPhPE consisting of greater than 50% (mol%) DPhPC formed unilamellar vesicles. If the total lipid concentration was greater than 0.15 g/l, then the vesicles formed solid-supported bilayers on plasma-treated gold and silica surfaces by the process of spontaneous vesicle adsorption and rupture, as determined by quartz crystal microbalance with dissipation monitoring and atomic force microscopy. The solid-supported bilayers exhibited a high degree of viscoelasticity, probably an effect of relatively high amounts of imbibed water or incomplete vesicle fusion. Lipid compositions consisting of greater than 50% DPhPE formed small flower-like vesicular structures along with discrete liquid crystalline structures, as evidenced by cryogenic transmission electron microscopy. Furthermore, electrophysiology measurements were performed on bilayers using the tip-dip methodology and the bilayers' capacity to retain its electrical resistance towards an applied potential across the bilayer was evaluated as a function of lipid composition. It was shown that the lipid ratio significantly affected the bilayer's electrical stability, with pure DPhPE having the highest stability followed by 3DPhPC:7DPhPE and 7DPhPC:3DPhPE in decreasing order. The bilayer consisting of 5DPhPC:5DPhPE had the lowest stability towards the applied electrical potential.
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| 20. |
- Arslan Yildiz, Ahu, et al.
(author)
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Biomimetic membrane platform: Fabrication, characterization and applications
- 2013
-
In: Colloids and Surfaces B. - : Elsevier. - 0927-7765 .- 1873-4367. ; 103, s. 510-516
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Journal article (peer-reviewed)abstract
- A facile method for assembly of biomimetic membranes serving as a platform for expression and insertion of membrane proteins is described. The membrane architecture was constructed in three steps: (i) assembly/printing of alpha-laminin peptide (P19) spacer on gold to separate solid support from the membrane architecture; (ii) covalent coupling of different lipid anchors to the P19 layer to serve as stabilizers of the inner leaflet during bilayer formation; (iii) lipid vesicle spreading to form a complete bilayer. Two different lipid membrane systems were examined and two different P19 architectures prepared by either self-assembly or mu-contact printing were tested and characterized using contact angle (CA) goniometry, surface plasmon resonance (SPR) spectroscopy and imaging surface plasmon resonance (iSPR). It is shown that surface coverage of cushion layer is significantly improved by mu-contact printing thereby facilitating bilayer formation as compared to self-assembly. To validate applicability of proposed methodology, incorporation of Cytochrome bo(3) ubiquinol oxidase (Cyt-bo(3)) into biomimetic membrane was performed by in vitro expression technique which was further monitored by surface plasmon enhanced fluorescence spectroscopy (SPFS). The results showed that solid supported planar membranes, tethered by alpha-laminin peptide cushion layer, provide an attractive environment for membrane protein insertion and characterization.
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| 21. |
- Arvidsson, Sara, 1977-, et al.
(author)
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Detection of surface bound complement at increasing serum anticoagulant concentrations.
- 2008
-
In: Colloids and surfaces. B, Biointerfaces. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 62:2, s. 214-9
-
Journal article (peer-reviewed)abstract
- Surface mediated immune complement activation can be detected by a variety of antibody utilizing methods such as ELISA, fluorescence- or radiolabelling techniques, QCM, and ellipsometry. In the present work we investigated how the common anticoagulants heparin, dalteparin, fondaparinux and sodium citrate affected the binding of anti-complement factor 3c (anti-C3c) on a model complement activator surface, immobilised IgG, after incubation in human blood serum. The results show, as expected, that different anticoagulants affect the antibody binding differently. Increasing amounts of heparin, dalteparin and sodium citrate in normal serum resulted in a decreasing anti-C3c binding. The antibody deposition was not sensitive for the fondaparinux concentration. Surprisingly high concentrations of anti-coagulantia were needed to completely eradicate the antibody binding. Experiments in EGTA-serum showed that anticoagulants interfered directly with both the classical and alternative pathways. Control C3a-des arg ELISA measurements show that the lowered antibody surface binding was not a result of complement depletion in serum. Kallikrein generation by hydrophilic glass surfaces was not affected by high anticoagulant concentrations.
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| 22. |
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| 23. |
- Azuma, Tomoyuki, et al.
(author)
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Nano-structural comparison of 2-methacryloyloxyethyl phosphorylcholine- and ethylene glycol-based surface modification for preventing protein and cell adhesion
- 2017
-
In: Colloids and Surfaces B. - : Elsevier. - 0927-7765 .- 1873-4367. ; 159, s. 655-661
-
Journal article (peer-reviewed)abstract
- Polymer brush, owing to its precisely controllable nanostructure, has great potential for surface modification in the biomedical field. In this study, we evaluated the bio-inertness of polymer brush, monomer monolayers, and polymer-coated surfaces based on their structures, to identify the most effective bio-inert modification. We focused on two well-known bio-inert materials, 2-methacryloyloxyethyl phosphorylcholine (MPC) and ethylene glycol (EG). The amount of adsorbed proteins on the surface was found to be dependent on the monomer unit density in the case of MPC, whereas this correlation was not observed in the case of EG. Cell adhesion was suppressed on the brush structure of both MPC and EG units, regardless of their density. The brush structure of MPC and EG units showed better anti-protein and anti-cell-adhesion than monolayers and polymer-coated surfaces. Thus, the steric repulsion was not only important in EG units-based surface, but also in MPC-based surface. In addition, multiple polymer layers formed by MPC-based polymer coating also displayed similar properties. (C) 2017 Elsevier B.V. All rights reserved.
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| 24. |
- Barauskas, Justas, et al.
(author)
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Synthesis and aqueous phase behavior of 1-glyceryl monooleyl ether
- 2005
-
In: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 1873-4367 .- 0927-7765. ; 41:1, s. 49-53
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Journal article (peer-reviewed)abstract
- Synthesis of 1-glyceryl monooleyl ether (GME) has been accomplished yielding material of high purity (99.6%). The aqueous phase behavior of synthesized lipid has been investigated by using polarized microscopy and small angle X-ray diffraction. As a result, a partial temperature-composition phase diagram has been constructed. GME forms a reversed micellar solution and reversed hexagonal liquid crystalline phase at low and high hydration, respectively. The hexagonal phase coexists with excess water and is stable up to about 63 degreesC. These findings make GME an interesting alternative to glycerol monoesters in various fields of applications. (C) 2004 Elsevier B.V. All rights reserved.
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| 25. |
- Barauskas, Justas, et al.
(author)
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Thermomyces lanuginosus lipase-catalyzed hydrolysis of the lipid cubic liquid crystalline nanoparticles
- 2016
-
In: Colloids and Surfaces B. - : Elsevier. - 0927-7765 .- 1873-4367. ; 137, s. 50-59
-
Journal article (peer-reviewed)abstract
- In this study well-ordered glycerol monooleate (GMO)-based cubic liquid crystalline nanoparticles (LCNPs) have been used as substrates for Thermomyces lanuginosus lipase in order to establish the relation between the catalytic activity, measured by pH-stat titration, and the change in morphology and nano-structure determined by cryogenic transmission electron microscopy and synchrotron small angle X-ray diffraction. The initial lipase catalyzed LCNP hydrolysis rate is approximately 25% higher for large 350 nm nanoparticles compared to the small 190 nm particles, which is attributed to the increased number of structural defects on the particle surface. At pH 8.0 and 8.4 bicontinuous Im3m cubic LCNPs transform into "sponge"-like assemblies and disordered multilamellar onion-like structures upon exposure to lipase. At pH 6.5 and 7.5 lipolysis induced phase transitions of the inner core of the particles, following the sequence Im3m cubic -> reversed hexagonal -> reversed micellar Fd3m cubic -> reversed micelles. These transitions to the liquid crystalline phases with higher negative curvature of the lipid/water interface were found to trigger protonation of the oleic acid produced during lipase catalyzed reaction. The increase curvature of the reversed discrete micellar cubic phase was suggested to cause an increase in the oleic acid pK(a) to a larger value observed by pH-stat titration. (C) 2015 Elsevier B.V. All rights reserved.
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| 26. |
- Barbosa, Simone C., et al.
(author)
-
The Importance of Cyclic Structure for Labaditin on Its Antimicrobial Activity Against Staphylococcus aureus
- 2016
-
In: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 148, s. 453-459
-
Journal article (peer-reviewed)abstract
- Antimicrobial resistance has reached alarming levels in many countries, thus leading to a search for new classes of antibiotics, such as antimicrobial peptides whose activity is exerted by interacting specifically with the microorganism membrane. In this study, we investigate the molecular-level mechanism of action for Labaditin (Lo), a 10-amino acid residue cyclic peptide from Jatropha multifida with known bactericidal activity againstStreptococcus mutans. We show that Lo is also effective against Staphylococcus aureus(S. aureus) but this does not apply to its linear analogue (L1). Using polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS), we observed with that the secondary structure of Lo was preserved upon interacting with Langmuir monolayers from a phospholipid mixture mimicking S. aureus membrane, in contrast to L1. This structure preservation for the rigid, cyclic Lo is key for the self-assembly of peptide nanotubes that induce pore formation in large unilamellar vesicles (LUVs), according to permeability assays and dynamic light scattering measurements. In summary, the comparison between Labaditin (Lo) and its linear analogue L1 allowed us to infer that the bactericidal activity of Lo is more related to its interaction with the membrane. It does not require specific metabolic targets, which makes cyclic peptides promising for antibiotics without bacteria resistance.
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| 27. |
- Baydemir, Goezde, et al.
(author)
-
Bilirubin recognition via molecularly imprinted supermacroporous cryogels
- 2009
-
In: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 1873-4367 .- 0927-7765. ; 68:1, s. 33-38
-
Journal article (peer-reviewed)abstract
- Recent years molecular imprinting has received considerable attention as an excellent and simple approach to recognize small molecules and bioactive substances. The aim of this study is to prepare the bilirubin-imprinted supermacroporous cryogels which can be used for the adsorption of bilirubin from human plasma. N-methacryloyl(L)-tyrosinemethylester (MAT) was chosen as the preorganization monomer. In the first step, bilirubin was complexed with MAT and the bilirubin-imprinted poly(hydroxyethyl methacrylate-N-methacryloyl-(L)-tyrosine methylester) [BR-MIP] cryogel was produced by free radical polymerization initiated by N,N,N',N'-tetramethylene diamine (TEMED) and ammonium persulfate (APS) pair in an ice bath. After that, the template molecules (i.e., bilirubin) were removed from the polymeric structure using sodium carbonate and sodium hydroxide. The maximum bilirubin adsorption amount was 3.6 mg/g polymer. The relative selectivity coefficients of the BR-MIP cryogel for bilirubin/cholesterol and bilirubin/testosterone mixtures were 7.3 and 3.2 times greater than non-imprinted poly(HEMA-MAT) [NIP] cryogel, respectively. The BR-MIP cryogel could be used many times without decreasing bilirubin adsorption amount significantly. Therefore, as a reusable carrier possessing high selectivity, BR-MIP cryogel has a potential candidate as a clinical hemoperfusion material. (C) 2008 Elsevier B.V. All rights reserved.
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| 28. |
- Bełdowski, Piotr, et al.
(author)
-
Interactions of a short hyaluronan chain with a phospholipid membrane
- 2019
-
In: Colloids and Surfaces B. - : Elsevier B.V.. - 0927-7765 .- 1873-4367. ; 184
-
Journal article (peer-reviewed)abstract
- Hyaluronic acid and phospholipids are two components that are present in the synovial fluid, and both are implicated as important facilitators of joint lubrication. In this work we aim to clarify how hyaluronic acid interacts with a phospholipid bilayer through their molecular interactions at the bilayer surface. To this end we performed molecular dynamics simulations of one hyaluronic acid molecule at a phospholipid bilayer in aqueous solution. The simulations were carried out for two aqueous solutions of equal concentrations, containing either NaCl or CaCl2. We analyzed hydrogen bonds, hydrophobic contacts and cation mediated bridges to clarify how hyaluoronic acid binds to a phospholipid bilayer. The analysis shows that calcium ions promote longer lasting bonds between the species as they create calcium ion bridges between the carboxylate group of hyaluronic acid and the phosphate group of the phospholipid. This type of additional bonding does not significantly influence the total number of contact created, but rather stabilizes the contact. The presented results can facilitate understanding of the role of hyaluronic acid and phospholipid interactions in terms of lubrication of articular cartilage.
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| 29. |
- Bergstrand, A., et al.
(author)
-
Aggregation behavior and size of lipopolysaccharide from Escherichia coli O55:B5
- 2006
-
In: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 53:1, s. 42261-
-
Journal article (peer-reviewed)abstract
- 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.
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| 30. |
- Bergstrand, Anna, 1974, et al.
(author)
-
Towards a biosensor immunoassay of protein-bound isopeptides in human plasma
- 2008
-
In: Colloids and Surfaces B: Biointerfaces. - 0927-7765 .- 1873-4367. ; 66, s. 150-
-
Journal article (peer-reviewed)abstract
- This study demonstrates that synthetic isopeptides formed on BSA can be quantitatively analyzed by a surface plasmon resonance-based biosensor method. A monoclonal IgM antibody 81D4, that reacts with the synthetic isopeptide and also with the natural isopeptide cross-link in D-dimer (but not with its non-cross-linked fibrin monomer), was covalently immobilized to a carboxymethylated dextran surface, a CM5 surface. Its immunocapturing efficiency was found to be good. The affinity of the interaction between the monoclonal 81D4 and the synthetic isopeptide was estimated to approximately 4x10(-7)M. Good reactivity was also observed when human plasma spiked with this isopeptide was used as test solution. Cross-linked D-dimer in the plasma of patients is a marker of disseminated intravascular coagulation (DIC) which occurs late in sepsis. This biosensor method has the potential to be developed into a rapid sensitive assay for measuring the level of natural isopeptide cross-links in proteins in the plasma of patients with a suspected diagnosis of sepsis.
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| 31. |
- Berlind, Torun, 1965-, et al.
(author)
-
Formation and cross-linking of fibrinogen layers monitored with in situ spectroscopic ellipsometry
- 2010
-
In: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 75:2, s. 410-417
-
Journal article (other academic/artistic)abstract
- Thick matrices of fibrinogen with incorporation of a matrix metalloproteinaseinhibitor were covalently bonded on functionalized silicon surfaces using an ethyl-3-dimethyl-aminopropyl-carbodiimide and N-hydroxy-succinimide affinity ligand couplingchemistry. The growth of the structure was followed in situ using dynamic ellipsometryand characterized at steady-state with spectroscopic ellipsometry. The growth wascompared with earlier work on ex situ growth of fibrinogen layers studied by singlewavelength ellipsometry. It is found that in situ growth and ex situ growth yield differentstructural properties of the formed protein matrix. Fibrinogen matrices with thicknessesup to 58 nm and surface mass densities of 1.6 μg/cm2 have been produced.
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| 32. |
- Bhatnagar, Amit, et al.
(author)
-
Biosorption optimization of nickel removal from water using Punica granatum peel waste
- 2010
-
In: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 76:2, s. 544-548
-
Journal article (peer-reviewed)abstract
- The present Study was undertaken to evaluate the feasibility of Punica granatum (pomegranate) peel waste for the removal of nickel from water. Batch experiments were performed to study the biosorption of nickel on prepared pomegranate peel adsorbent. The sorption process was well explained with pseudo-second-order kinetic model. The maximum sorption capacity of pomegranate peel adsorbent for nickel removal was ca. 52 mg g(-1). The sorption has been found to be endothermic and data conform to the Langmuir model. The Gibbs free energy was determined to be negative, indicating the spontaneous nature of the sorption process. The results of the present study suggest that pomegranate peel waste can be used beneficially for nickel removal from aqueous solution.
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| 33. |
- Borro, Bruno C., et al.
(author)
-
Microgels and hydrogels as delivery systems for antimicrobial peptides
- 2020
-
In: Colloids and Surfaces B. - : ELSEVIER. - 0927-7765 .- 1873-4367. ; 187
-
Journal article (peer-reviewed)abstract
- Due to rapid development of bacterial resistance against antibiotics, an emerging health crisis is underway, where `simple' infections may no longer be treatable. Antimicrobial peptides (AMPs) constitute a class of substances attracting interest in this context. So far, research on AMPs has primarily focused on the identification of potent and selective peptides, as well as on the action mode of such peptides. More recently, there has been an increasing awareness that the delivery of AMPs is challenging due to their size, net positive charge, amphiphilicity, and proteolytic susceptibility. Hence, successful development of AMP therapeutics will likely require also careful design of efficient AMP delivery systems. In the present brief review, we discuss microgels, as well as related polyelectrolyte complexes and macroscopic hydrogels, as delivery systems for AMPs. In doing so, key factors for peptide loading and release are outlined and exemplified, together with consequences of this for functional performance relating to antimicrobial effects and cell toxicity.
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| 34. |
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| 35. |
- Bramer, Tobias, et al.
(author)
-
Implications of regular solution theory on the release mechanism of catanionic mixtures from gels
- 2009
-
In: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 71:2, s. 214-225
-
Journal article (peer-reviewed)abstract
- The aim of this study was to apply the regular solution theory of mixed micelles to gain new insights on the drug release mechanism, when using catanionic mixtures as a method of obtaining prolonged release from gels. Synergistic effects were investigated at equilibrium and quantified in terms of regular solution theory interaction parameters. The drug release from catanionic aggregates was studied both in a polymer free environment, using dialysis membranes, and in gels, using a modified LISP paddle method. The drug release kinetics was modelled theoretically by combining the regular solution theory with Fick's diffusion laws assuming a contribution to the transport only from monomeric species (stationary aggregates). The theoretical predictions were found to be in reasonably good agreement with experiments. An analysis of the calculated distribution of species between aggregated and monomeric states was shown to provide further insights into the release mechanism.
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| 36. |
- Browning, Kathryn L., et al.
(author)
-
Effect of bilayer charge on lipoprotein lipid exchange
- 2018
-
In: Colloids and Surfaces B. - : ELSEVIER SCIENCE BV. - 0927-7765 .- 1873-4367. ; 168, s. 117-125
-
Journal article (peer-reviewed)abstract
- Lipoproteins play a key role in the onset and development of atherosclerosis, the formation of lipid plaques at blood vessel walls. The plaque formation, as well as subsequent calcification, involves not only endothelial cells but also connective tissue, and is closely related to a wide range of cardiovascular syndromes, that together constitute the number one cause of death in the Western World. High (HDL) and low (LDL) density lipoproteins are of particular interest in relation to atherosclerosis, due to their protective and harmful effects, respectively. In an effort to elucidate the molecular mechanisms underlying this, and to identify factors determining lipid deposition and exchange at lipid membranes, we here employ neutron reflection (NR) and quartz crystal microbalance with dissipation (QCM-D) to study the effect of membrane charge on lipoprotein deposition and lipid exchange. Dimyristoylphosphatidylcholine (DMPC) bilayers containing varying amounts of negatively charged dimyristoylphosphatidylserine (DMPS) were used to vary membrane charge. It was found that the amount of hydrogenous material deposited from either HDL or LDL to the bilayer depends only weakly on membrane charge density. In contrast, increasing membrane charge resulted in an increase in the amount of lipids removed from the supported lipid bilayer, an effect particularly pronounced for LDL. The latter effects are in line with previously reported observations on atherosclerotic plaque prone regions of long-term hyperlipidaemia and type 2 diabetic patients, and may also provide some molecular clues into the relation between oxidative stress and atherosclerosis.
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| 37. |
- Chakraborty, Subhashis, et al.
(author)
-
Utilization of adsorption technique in the development of oral delivery system of lipid based nanoparticles
- 2010
-
In: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 81:2, s. 563-569
-
Journal article (peer-reviewed)abstract
- The objective of the present study was to employ suitable adsorbent with free flowing characteristics for improving the stability and physical properties of solid lipid nanoparticles (SLN) for oral administration. Stearic acid based nanoparticles of carvedilol phosphate were fabricated by solvent emulsification evaporation technique in sodium taurocholate solution prepared in pH 7.2 buffers (I-KH2PO4/NaOH or II-NaH2PO4/Na2HPO4) with 1% polyvinyl alcohol. Nanoparticles were then adsorbed by passing the nanodispersion through a Neusilin US2 (adsorbent) column. Interestingly, scanning electron microscopy revealed round deformed and even collapsed nanoparticles in Buffer-I and discrete spherical to ellipsoidal nanoparticles in Buffer-II which indicates the inability of nanoemulsion to crystallize and form SLN in Buffer-I. The successful formation of SLN in Buffer-II was confirmed by differential scanning calorimetry and X-ray diffraction. The retention of SLN from the nanodispersion by adsorption on the adsorbent imparted good flow property and resulted in a marked stability improvement of the formulation in terms of drug retention efficiency and release profile as compared to the simple nanosuspension. In conclusion, the adsorbent technology would be instrumental in imparting additional features to the existing conventional colloidal system for pharmaceutical application which would ease the process of capsule filling at industrial scale, simplify the handling of formulations by patients and can significantly improve the shelf life of the product for a longer period of time as compared to liquid formulations
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| 38. |
- Chatzidaki, Maria D., et al.
(author)
-
Microemulsion versus emulsion as effective carrier of hydroxytyrosol
- 2016
-
In: Colloids and Surfaces B. - : Elsevier. - 0927-7765 .- 1873-4367. ; 137:1, s. 146-151
-
Journal article (peer-reviewed)abstract
- Two edible Water-in-Oil (W/O) dispersions, an emulsion that remains kinetically stable and a microemulsion which is spontaneously formed, transparent and thermodynamically stable, were developed for potential use as functional foods, due to their ability to be considered as matrices to encapsulate biologically active hydrophilic molecules. Both systems contained Medium Chain Triglycerides (MCT) as the continuous phase and were used as carriers of Hydroxytyrosol (HT), a hydrophilic antioxidant of olive oil. A low energy input fabrication process of the emulsion was implemented. The obtained emulsion contained 1.3% (w/w) of surfactants and 5% (w/w) aqueous phase. The spontaneously formed microemulsion contained 4.9% (w/w) of surfactants and 2% (w/w) aqueous phase. A comparative study in terms of structural characterization of the systems in the absence and presence of HT was carried out. Particle size distribution obtained by Dynamic Light Scattering (DLS) technique and interfacial properties of the surfactants' layer, examined by Electron Paramagnetic Resonance (EPR) spectroscopy indicated the involvement of HT in the surfactant membrane. Finally, the proposed systems were studied for the scavenging activity of the encapsulated antioxidant toward galvinoxyl stable free radical showing a high scavenging activity of HT in both systems.
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| 39. |
- Chronakis, I S, et al.
(author)
-
Complex formation in aqueous medium of partially hydrolysed oat cereal proteins with sodium stearoyl-2 lactylate (SSL) lipid surfactant and implications for bile acids activity
- 2004
-
In: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 1873-4367 .- 0927-7765. ; 35:3-4, s. 175-184
-
Journal article (peer-reviewed)abstract
- Sodium stearoyl-2 lactylate (SSL) lipid surfactant molecules specifically bind partially hydrolysed oat proteins in aqueous medium and significantly enhance the dispersion stability of oat cereal preparations. The proposed complexation is composition dependent and a greater understanding of the role of both oat proteins and lipid surfactant in the effect was gained with data from high performance liquid chromatography (HPLC-UV), viscometry and differential scanning micro calorimetry. The effect of the lipid surfactant on the degree of association is primarily governed by the conformational activity of oat protein molecules related to the extent of protein hydrolysed state, as well as protein unfolded and subsequent aggregated structures. SSL does not dissociate oat proteins into subunits or destroy important hydrophobic contacts already stabilising the protein molecules. Although the exact mode of association is unknown, the present study demonstrates that such interactions occur in a specific manner and suggest selectivity of oat proteins for individual fatty acids. The effect of various amounts of bile acids on SSL-oat protein interaction was also investigated, as a first attempt to investigate the role of lipid surfactant molecules in the known cholesterol-lowering action of oat cereal ingredients and to elucidate favourable conditions by which oat cereal can elicit hypocholesterolemic effects. (C) 2004 Elsevier B.V. All rights reserved.
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| 40. |
- Chudinova, Ekaterina A., et al.
(author)
-
Adhesion, proliferation, and osteogenic differentiation of human mesenchymal stem cells on additively manufactured Ti6Al4V alloy scaffolds modified with calcium phosphate nanoparticles
- 2019
-
In: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 176, s. 130-139
-
Journal article (peer-reviewed)abstract
- In the present study, biocomposites based on 3D porous additively manufactured Ti6Al4V (Ti64) scaffolds modified with biocompatible calcium phosphate nanoparticles (CaPNPs) were investigated. Ti64 scaffolds were manufactured via electron beam melting technology using an Arcam machine. Electrophoretic deposition was used to modify the scaffolds with CaPNPs, which were synthesized by precipitation in the presence of polyethyleneimine (PEI). Dynamic light scattering revealed that the CaP/PEI nanoparticles had an average size of 46 ± 18 nm and a zeta potential of +22 ± 9 mV. Scanning electron microscopy (SEM) revealed that the obtained spherical CaPNPs had an average diameter of approximately 90 nm. The titanium-based scaffolds coated with CaPNPs exhibited improved hydrophilic surface properties, with a water contact angle below 5°. Cultivation of human mesenchymal stem cells (hMSCs) on the CaPNPs-coated Ti64 scaffolds indicated that the improved hydrophilicity was beneficial for the attachment and growth of cells in vitro. The Ti6Al4V/CaPNPs scaffold supported an increase in the alkaline phosphatase (ALP) activity of cells. In addition to the favourable cell proliferation and differentiation, Ti6Al4V/CaPNPs scaffolds displayed increased mineralization compared to non-coated Ti6Al4V scaffolds. Thus, the developed composite 3D scaffolds of Ti6Al4V functionalized with CaPNPs are promising materials for different applications related to bone repair.
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| 41. |
- Costa, Diana, et al.
(author)
-
Swelling behavior of a new biocompatible plasmid DNA hydrogel
- 2012
-
In: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 1873-4367 .- 0927-7765. ; 92, s. 106-112
-
Journal article (peer-reviewed)abstract
- Chemical plasmid DNA (pDNA) gels were prepared by a cross-linking reaction with ethylene glycol diglycidyl ether (EGDE). Fluorescence microscopy (FM) and scanning electron microscopy (SEM) images of pDNA gels are reported. For the first time, the pDNA gels have been investigated with respect to their swelling in aqueous solution containing different additives, such as metal ions, polyamines, polycations and surfactants. The effect of the cationic surfactant tail length on the volume phase transition of pDNA gels was studied as a function of surfactant concentration: the critical aggregation concentration (cac), is found to decrease with increasing length of the hydrophobic tail. The deswelling appears to be reversible as exemplified by the addition of anionic surfactant subsequent to collapsing the gel by a cationic surfactant. Cell viability assays suggest that the plasmid DNA gels are non-toxic to cells and do not cause any distinct harm to them. This step contributes to the possibility of using these gels, as carriers, in real biological systems. (C) 2011 Elsevier B.V. All rights reserved.
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| 42. |
- Cozzolino, C. A., et al.
(author)
-
Exploiting the nano-sized features of microfibrillated cellulose (MFC) for the development of controlled-release packaging
- 2013
-
In: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 110, s. 208-216
-
Journal article (peer-reviewed)abstract
- Microfibrillated cellulose (MFC) was used in this study to prepare films containing an active molecule, lysozyme, which is a natural antimicrobial agent. The main goal of this research was to assess the potential for exploiting the nano-sized dimension of cellulose fibrils to slow the release of the antimicrobial molecule, thus avoiding a too-quick release into the surrounding medium, which is a major disadvantage of most release systems. For this purpose, the release kinetics of lysozyme over a 10-day period in two different media (pure water and water/ethanol 10. wt.%) were obtained, and the experimental data was fitted with a solution of Fick's second law to quantify the apparent diffusion coefficient (D). The results indicate that the MFC retained lysozyme, presumably due to electrostatic, hydrogen, and ion-dipole interactions, with the largest release of lysozyme-approximately 14%-occurring from the initial amount loaded on the films. As expected, ethanol as a co-solvent slightly decreased the diffusion of lysozyme from the MFC polymer network. The addition of two potential modulating release agents-glycerol and sodium chloride-was also evaluated. Findings from this work suggest that MFC-based films can be considered a suitable candidate for use in controlled-release packaging systems.
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| 43. |
- Craig, Marina, 1978, et al.
(author)
-
Bacterial protease triggered release of biocides from microspheres with an oily core
- 2015
-
In: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 127, s. 200-205
-
Journal article (peer-reviewed)abstract
- This study deals with controlled release of drugs to a Staphylococcus aureus infected site from microspheres with an oily core and a polymeric shell. The intended use of the microspheres is for chronic wounds and the microspheres may be administered in the form of a wash liquid or incorporated in a gel. Chronic wounds often carry infection, and the use of microspheres with drug release triggered by the bacterial infection is therefore of interest. A lipophilic drug or a model of the drug was dissolved in an oil and the oil phase was dispersed into an o/w emulsion. A nanofilm shell was then assembled around the oil droplets with the layer-by-layer technique using the two biodegradable polypeptides anionic poly-L-glutamic acid (PLGA) and cationic poly-L-lysine (PLL). Since S. aureus exudes proteases such as glutamyl endopeptidase (V8) during colonization and infection, its substrate specificity was key when assembling the nanofilm. Since V8 is known to be substrate specific to the Glu-X bond, PLGA was chosen as the terminating layer of the nanofilm. Crosslinking the nanofilm after assembly lead to increased stability of the microspheres. It was shown that in a non-infectious environment, i.e. when a human wound enzyme, HNE (human neutrophile elastase), was present, the microspheres remained intact. The staphylococcal protease V8, on the other hand, readily catalyzed degradation of the microspheres, thus releasing the drug when triggered by the infectious environment.
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| 44. |
- Cuomo, Francesca, et al.
(author)
-
In-vitro digestion of curcumin loaded chitosan-coated liposomes
- 2018
-
In: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 168, s. 29-34
-
Journal article (peer-reviewed)abstract
- Liposomes are considered a major route for encapsulation of hydrophilic and hydrophobic molecules. Chitosan coated liposomes could represent an alternative way as a carrier for delivery of drugs in human body. In this study the preparation and applicability of chitosan-coated liposomes containing curcumin as well as curcumin loaded anionic liposomes were evaluated. The applicability of the carriers was tested by means of an in vitro digestion procedure allowing for measurement of the bioaccessibility of ingested curcumin. Values of diameter, polydispersity index and surface charge for curcumin loaded anionic liposomes obtained through dynamic light scattering and zeta-potential measurements were 129 nm, 0.095 and -49 mV, respectively. After chitosan-coating, diameter and polydispersity index remain unvaried while the surface charge gets positive. Slightly higher curcumin concentrations were found after the mouth and the stomach digestion phases when curcumin was loaded in anionic liposomes. On the contrary, after the intestinal phase, a higher percentage of curcumin was found when chitosan-coated liposomes were used as carrier, both in the raw digesta and in the bile salt micellar phase. It was shown that the presence of a positively charged surface allows a better absorption of curcumin in the small intestine phase, which increases the overall curcumin bioavailability. The mechanism behind these results can be understood from the composition of different environments generated by the digestive fluids that differently interact with anionic or cationic surfaces.
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| 45. |
- Dew, Noel, et al.
(author)
-
Gel formation in systems composed of drug containing catanionic vesicles and oppositely charged hydrophobically modified polymer.
- 2009
-
In: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 70:2, s. 187-197
-
Journal article (peer-reviewed)abstract
- The aim of this study was to explore if mixtures of drug containing catanionic vesicles and polymers give rise to gel formation, and if so, if drug release from these gels could be prolonged. Catanionic vesicles formed from the drug substances alprenolol or tetracaine, and the oppositely charged surfactant sodium dodecyl sulphate were mixed with polymers. Three polymers with different properties were employed: one bearing hydrophobic modifications, one positively charged and one positively charged polymer bearing hydrophobic modifications. The structure of the vesicles before and after addition of polymer was investigated by using cryo-TEM. Gel formation was confirmed by using rheological measurements. Drug release was studied using a modified USP paddle method. Gels were observed to form only in the case when catanionic vesicles, most likely with a net negative charge, were mixed with positively charged polymer bearing lipophilic modifications. The release of drug substance from these systems, where the vesicles are not trapped within the gel but constitute a founding part of it, could be significantly prolonged. The drug release rate was found to depend on vesicle concentration to a higher extent than on polymer concentration.
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| 46. |
- Dew, Noel, 1980-, et al.
(author)
-
Gel formulations containing catanionic vesicles composed of alprenolol and SDS : effects of drug release and skin penetration on aggregate structure
- 2012
-
In: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 89, s. 53-60
-
Journal article (peer-reviewed)abstract
- To fully utilize the extended contact time of gel formulations a novel formulation with drug containing catanionic aggregates offering prolonged drug release and skin penetration were investigated. This study aimed to further explore the drug release process from catanionic vesicles in gels. Catanionic vesicles were formed from alprenolol and sodium dodecyl sulphate. Physical gels composed of catanionic vesicles and a SoftCAT polymer were used as well as covalent Carbopol gels. Drug release was measured in vitro using a modified USP paddle method and the skin penetration was studied using dermatomized pig ear skin mounted in horizontal Ussing chambers. The aggregate structure was visualized with cryo-TEM during the drug release and skin penetration process. The study results show that catanionic vesicles are present in the formulations throughout the drug release process and during the clinically relevant skin application time. Hence, the decreased skin penetration rate stems from the prolonged release of drug substance from the gels. The rheological investigation shows that the gel structure of the physically cross-linked gels is maintained even as the drug substance is released and the gel volume is decreased.These findings indicate that the applicability of formulations like these is a future possibility.
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| 47. |
- Dilgin, Yusuf, et al.
(author)
-
Electrocatalytic oxidation of NADH using a pencil graphite electrode modified with quercetin
- 2013
-
In: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 1873-4367 .- 0927-7765. ; 102, s. 816-821
-
Journal article (peer-reviewed)abstract
- In the present study, the electrocatalytic oxidation of reduced beta nicotinamide adenine dinucleotide (NADH) was investigated using a pencil graphite electrode modified with quercetin (PGE/QH(2)). The PGE/QH(2) was prepared through two steps: (i) the pre-treatment of PGE at 1.40V vs. Ag vertical bar AgCl vertical bar KCl(sat.) in pH 7.0 phosphate buffer containing 0.1 M KCl for 60 s and (ii) adsorption of QH(2) on the PGE via immersion of PGE into a 1.0 mM QH(2) solution (in ethanol) for 60 s. Cyclic voltammetric studies show that the peak potential of NADH oxidation shifts from +500 mV at bare PGE to +300 mV at PGE/QH(2). The electrocatalytic currents obtained from amperometric measurements at +300 mV vs. Ag vertical bar AgCl vertical bar KCl(sat.) and in phosphate buffer solution at pH 7.0 containing 0.1 M KCl were linearly related to the concentration of NADH. Linear calibration plots are obtained in the concentration range from 0.5 mu M to 100 mu M. The limit of detection was found to be 0.15 mu M. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.
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| 48. |
- Dimitrievski, Kristian, 1974, et al.
(author)
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Simulations of lipid transfer between a supported lipid bilayer and adsorbing vesicles
- 2010
-
In: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 75:2, s. 454-465
-
Journal article (peer-reviewed)abstract
- Recent experiments demonstrate transfer of lipid molecules between a charged, supported lipid membrane (SLB) and vesicles of opposite charge when the latter adsorb on the SLB. A simple phenomenological bead model has been developed to simulate this process. Beads were defined to be of three types, 'n', 'p', and '0', representing POPS (negatively charged), POEPC (positively charged), and POPC (neutral but zwitterionic) lipids, respectively. Phenomenological bead-bead interaction potentials and lipid transfer rate constants were used to account for the overall interaction and transfer kinetics. Using different bead mixtures in both the adsorbing vesicle and in the SLB (representing differently composed/charged vesicles and SLBs as in the reported experiments), we clarify under which circumstances a vesicle adsorbs to the SLB, and whether it, after lipid transfer and changed composition of the SLB and vesicle, desorbs back to the bulk again or not. With this model we can reproduce and provide a conceptual picture for the experimental findings
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| 49. |
- Dineshram, R., et al.
(author)
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Biofouling studies on nanoparticle-based metal oxide coatings on glass coupons exposed to marine environment
- 2009
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In: Colloids and Surfaces B. - 0927-7765 .- 1873-4367. ; 74:1, s. 75-83
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Journal article (peer-reviewed)abstract
- Titania, niobia and silica coatings, derived from their respective nanoparticle dispersions or sols and fabricated on soda lime glass substrates were subjected to field testing in marine environment for anti-macrofouling applications for marine optical instruments. Settlement and enumeration of macrofouling organisms like barnacles, hydroides and oysters on these nanoparticle-based metal oxide coatings subjected to different heat treatments up to 400 degrees C were periodically monitored for a period of 15 days. The differences observed in the antifouling behaviour between the coated and uncoated substrates are discussed based on the solar ultraviolet light induced photocatalytic activities as well as hydrophilicities of the coatings in case of titania and niobia coatings and the inherent hydrophilicity in the case of silica coating. The effect of heat treatment on the photocatalytic activity of the coatings is also discussed. (C) 2009 Elsevier B.V. All rights reserved.
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| 50. |
- Duehrkop, Claudia, et al.
(author)
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Development and characterization of an innovative heparin coating to stabilize and protect liposomes against adverse immune reactions
- 2016
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In: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 141, s. 576-583
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Journal article (peer-reviewed)abstract
- Liposomes have been recognized as excellent drug delivery systems, but when they come in direct contact with different blood components they may trigger an immediate activation of the innate immune system. The aim of the present study was to produce long-circulating, blood-compatible liposomes by developing a construct of liposomes covered by a novel unique heparin complex (CHC; 70 heparin molecules per complex) to avoid recognition by the innate immune system. Unilamellar, cationic liposomes were produced by hand extrusion through a 100-nm polycarbonate membrane. Coating of liposomes with the macromolecular CHC was accomplished by electrostatic interactions. Dynamic light scattering as well as QCM-D measurements were used to verify the electrostatic deposition of the negatively charged CHC to cationic liposomes. The CHC-coated liposomes did not aggregate when in contact with lepirudin anti coagulated plasma. Unlike previous attempts to coat liposomes with heparin, this technique produced freely moveable heparin strands sticking out from the liposome surface, which exposed AT binding sites reflecting the anticoagulant potentials of the liposomes. In experiments using lepirudin-anticoagulated plasma, CHC-coated liposomes, in contrast to non-coated control liposomes, did not activate the complement system, as evidenced by low C3a and sC5b-9 generation and reduced leakage from the liposomes. In conclusion, we show that liposomes can be successfully coated with the biopolymer CHC, resulting in biocompatible and stable liposomes that have significant application potential. (C) 2016 Elsevier B.V. All rights reserved.
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