| 1. |
- Fang, Zhao, 1986, et al.
(author)
-
TiO2 nanoparticle interactions with supported lipid membranes – an example of removal of membrane patches
- 2016
-
In: RSC Advances. - 2046-2069. ; 6:94, s. 91102-91110
-
Journal article (peer-reviewed)abstract
- There is a need for different levels of model systems for effect studies of engineered nanoparticles and the development of nanoparticle structure–activity relationships in biological systems. Descriptors for nanoparticles based on their interactions in molecular model systems may become useful to predict toxicological responses of the nanoparticles in cells. Towards this end, we report on nanoparticle-induced formation of holes in supported model membranes. Specifically, TiO2 nanoparticle – lipid membrane interactions were studied under low ionic strength, basic conditions (pH 8), using different membrane compositions and several surface-sensitive analytical techniques. It was found that for mixed POPC/POPG (PG fractions ≥ 35%) membranes on silica supports, under conditions where electrostatic repulsion was expected, the addition of TiO2 nanoparticles resulted in transient interaction curves, consistent with the removal of part of the lipid membrane. The formation of holes was inferred from quartz crystal microbalance with dissipation (QCM-D) monitoring, as well as from optical measurements by reflectometry, and also verified by atomic force microscopy (AFM) imaging. The interaction between the TiO2 nanoparticles and the PG-containing membranes was dependent on the presence of Ca2+ ions. A mechanism is suggested where TiO2 nanoparticles act as scavengers of Ca2+ ions associated with the supported membrane, leading to weakening of the interaction between the membrane and the support and subsequent removal of lipid mass as TiO2 nanoparticles spontaneously leave the surface. This mechanism is consistent with the observed formation of holes in the supported lipid membranes.
|
|
| 2. |
- Zhao, Fang, et al.
(author)
-
TiO2 nanoparticle interactions with supported lipid membranes – an example of removal of membrane patches
- 2016
-
In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:94, s. 91102-91110
-
Journal article (peer-reviewed)abstract
- There is a need for different levels of model systems for effect studies of engineered nanoparticles and the development of nanoparticle structure–activity relationships in biological systems. Descriptors for nanoparticles based on their interactions in molecular model systems may become useful to predict toxicological responses of the nanoparticles in cells. Towards this end, we report on nanoparticle-induced formation of holes in supported model membranes. Specifically, TiO2 nanoparticle – lipid membrane interactions were studied under low ionic strength, basic conditions (pH 8), using different membrane compositions and several surface-sensitive analytical techniques. It was found that for mixed POPC/POPG (PG fractions ≥ 35%) membranes on silica supports, under conditions where electrostatic repulsion was expected, the addition of TiO2 nanoparticles resulted in transient interaction curves, consistent with the removal of part of the lipid membrane. The formation of holes was inferred from quartz crystal microbalance with dissipation (QCM-D) monitoring, as well as from optical measurements by reflectometry, and also verified by atomic force microscopy (AFM) imaging. The interaction between the TiO2 nanoparticles and the PG-containing membranes was dependent on the presence of Ca2+ ions. A mechanism is suggested where TiO2 nanoparticles act as scavengers of Ca2+ ions associated with the supported membrane, leading to weakening of the interaction between the membrane and the support and subsequent removal of lipid mass as TiO2 nanoparticles spontaneously leave the surface. This mechanism is consistent with the observed formation of holes in the supported lipid membranes.
|
|
| 3. |
- Aggarwal, N., et al.
(author)
-
Effect of Molecular Composition of Heparin and Cellulose Sulfate on Multilayer Formation and Cell Response
- 2013
-
In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 29:45, s. 13853-13864
-
Journal article (peer-reviewed)abstract
- Here, the layer-by-layer method was applied to assemble films from chitosan paired with either heparin or a semisynthetic cellulose sulfate (CS) that possessed a higher sulfation degree than heparin. Ion pairing was exploited during multilayer formation at pH 4, while hydrogen bonding is likely to occur at pH 9. Effects of polyanions and pH value during layer formation on multilayers properties were studied by surface plasmon resonance ("dry layer mass"), quartz crystal microbalance with dissipation monitoring ("wet layer mass"), water contact angle, and zeta potential measurements. Bioactivity of multilayers was studied regarding fibronectin adsorption and adhesion/proliferation of C2C12 myoblast cells. Layer growth and dry mass were higher for both polyanions at pH 4 when ion pairing occurred, while it decreased significantly with heparin at pH 9. By contrast, CS as polyanion resulted also in high layer growth and mass at pH 9, indicating a much stronger effect of hydrogen bonding between chitosan and CS. Water contact angle and zeta potential measurements indicated a more separated structure of multilayers from chitosan and heparin at pH 4, while CS led to a more fuzzy intermingled structure at both pH values. Cell behavior was highly dependent on pH during multilayer formation with heparin as polyanion and was closely related to fibronectin adsorption. By contrast, CS and chitosan did not show such dependency on pH value, where adhesion and growth of cells was high. Results of this study show that CS is an attractive candidate for multilayer formation that does not depend so strongly on pH during multilayer formation. In addition, such multilayer system also represents a good substrate for cell interactions despite the rather soft structure. As previous studies have shown specific interaction of CS with growth factors, multilayers from chitosan and CS may be of great interest for different biomedical applications.
|
|
| 4. |
- Aggarwal, N., et al.
(author)
-
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.
|
|
| 5. |
|
|
| 6. |
- Altgärde, Noomi, 1983, et al.
(author)
-
Immobilization of chondroitin sulfate to lipid membranes and its interactions with ECM proteins
- 2013
-
In: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 390:1, s. 528-266
-
Journal article (peer-reviewed)abstract
- Glycosaminoglycans (GAGs) in the extracellular matrix (ECM) have multiple functions in tissues including providing support, mediating cell division and differentiation, and taking part in important interactions with proteins, e.g. growth factors. Studying GAG related interactions is inherently difficult and requires suit- able interaction platforms. We show two strategies to covalently couple the GAG chondroitin sulfate (CS) to supported lipid bilayers (SLBs), either by (a) activating carboxy-functionalized phospholipids in the lipid bilayer, followed by the addition of hydrazide-functionalized CS, or by (b) activating naturally occurring carboxyl groups on CS prior to addition to an amino-functionalized SLB. Bilayer formation and subsequent immobilization was followed in real-time using the Quartz Crystal Microbalance with Dissipation monitor- ing, a technique that provides unique information when studying highly hydrated molecular films. The two strategies yielded thin CS films (in the nanometer range) with similar viscoelastic properties. Fluidity of the lipid bilayer was retained when CS was coupled. The application of the CS interaction platform was exemplified for type I collagen and the bone inducing growth factor bone morphogenetic protein-2 (BMP-2). The addition of collagen to immoblized CS resulted in soft layers whereas layers formed by addition of BMP-2 were denser, independent on the immobilization strategy used.
|
|
| 7. |
- Altgärde, Noomi, 1983, et al.
(author)
-
Mucin-like region of herpes simplex virus type 1 attachment protein gC modulates the virus-glycosaminoglycan interaction.
- 2015
-
In: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 290:35, s. 21473-21485
-
Journal article (peer-reviewed)abstract
- Glycoprotein C (gC) mediates the attachment of herpes simplex virus type 1 (HSV-1) to susceptible host cells by interacting with glycosaminoglycans (GAGs) on the cell surface. gC contains a mucin-like region located near the GAG-binding site, which may affect the binding activity. Here, we address this issue by studying an HSV-1 mutant lacking the mucin- like domain in gC and the corresponding purified mutant protein (gCΔmuc), in cell culture and GAG-binding assays, respectively. The mutant virus exhibited two functional alterations as compared to native HSV-1, i.e. decreased sensitivity to GAG-based inhibitors of virus attachment to cells, and reduced release of viral particles from the surface of infected cells. Kinetic and equilibrium binding characteristics of purified gC were assessed using surface plasmon resonance-based sensing together with a surface platform consisting of end-on immobilized GAGs. Both native gC and gCΔmuc bound via the expected binding region to chondroitin sulfate and sulfated hyaluronan but not to the non-sulfated hyaluronan, confirming binding specificity. In contrast to native gC, gCΔmuc exhibited a decreased affinity for GAGs and a slower dissociation, indicating that once formed, the gCΔmuc-GAG complex is more stable. It was also found that a larger number of gCΔmuc bound to a single GAG chain, compared to native gC. Taken together, our data suggest that the mucin-like region of HSV-1 gC is involved in the modulation of the GAG-binding activity, a feature of importance both for unrestricted virus entry into the cells and release of newly produced viral particles from infected cells.
|
|
| 8. |
- Altgärde, Noomi, 1983, et al.
(author)
-
Probing the biofunctionality of biotinylated hyaluronan and chondroitin sulfate by hyaluronidase degradation and aggrecan interaction
- 2013
-
In: Acta Biomaterialia. - : Elsevier BV. - 1878-7568 .- 1742-7061. ; 9:9, s. 8158-8166
-
Journal article (peer-reviewed)abstract
- Molecular interactions involving glycosaminoglycans (GAGs) are important for biological processes in the extracellular matrix (ECM) and at cell surfaces, and also in biotechnological applications. Enzymes in the ECM constantly modulate the molecular structure and the amount of GAGs in our tissues. Specifically, the changeable sulfation patterns of many GAGs are expected to be important in interactions with proteins. Biotinylation is a convenient method for immobilizing molecules to surfaces. When studying interactions at the molecular, cell and tissue level, the native properties of the immobilized molecule, i.e. its biofunctionality, need to be retained upon immobilization. Here, the GAGs hyaluronan (HA) and chondroitin sulfate (CS), and synthetically sulfated derivatives of the two, were immobilized using biotin-streptavidin binding. The degree of biotinylation and the placement of biotin groups (end-on/side-on) were varied. The introduction of biotin groups could have unwanted effects on the studied molecule, but this aspect that is not always straightforward to evaluate. Hyaluronidase, an enzyme that degrades HA and CS in the ECM, was investigated as a probe to evaluate the biofunctionality of the immobilized GAGs, using both quartz crystal microbalance and high-performance liquid chromatography. Our results showed that end-on biotinylated HA was efficiently degraded by hyaluronidase, whereas already a low degree of side-on biotinylation destroyed the degrading ability of the enzyme. Synthetically introduced sulfate groups also had this effect. Hence hyaluronidase degradation is a cheap and easy way to investigate how molecular function is influenced by the introduced functional groups. Binding experiments with the proteoglycan aggrecan emphasized the influence of protein size and surface orientation of the GAGs for in-depth studies of GAG behavior.
|
|
| 9. |
- Aneheim, Emma, 1982, et al.
(author)
-
Synthesis and Evaluation of Astatinated N-[2-(Maleimido)ethyl]-3-(trimethylstannyl)benzamide Immunoconjugates
- 2016
-
In: Bioconjugate chemistry. - : American Chemical Society (ACS). - 1520-4812 .- 1043-1802. ; 27:3, s. 688-97
-
Journal article (peer-reviewed)abstract
- Effective treatment of metastasis is a great challenge in the treatment of different types of cancers. Targeted alpha therapy utilizes the short tissue range (50-100 μm) of α particles, making the method suitable for treatment of disseminated occult cancers in the form of microtumors or even single cancer cells. A promising radioactive nuclide for this type of therapy is astatine-211. Astatine-211 attached to tumor-specific antibodies as carrier molecules is a system currently under investigation for use in targeted alpha therapy. In the common radiolabeling procedure, astatine is coupled to the antibody arbitrarily on lysine residues. By instead coupling astatine to disulfide bridges in the antibody structure, the immunoreactivity of the antibody conjugates could possibly be increased. Here, the disulfide-based conjugation was performed using a new coupling reagent, maleimidoethyl 3-(trimethylstannyl)benzamide (MSB), and evaluated for chemical stability in vitro. The immunoconjugates were subsequently astatinated, resulting in both high radiochemical yield and high specific activity. The MSB-conjugate was shown to be stable with a long shelf life prior to the astatination. In a comparison of the in vivo distribution of the new immunoconjugate with other tin-based immunoconjugates in tumor-bearing mice, the MSB conjugation method was found to be a viable option for successful astatine labeling of different monoclonal antibodies.
|
|
| 10. |
|
|
| 11. |
- Briand, Elisabeth, 1979, et al.
(author)
-
An OEGylated thiol monolayer for the tethering of liposomes and the study of liposome interactions
- 2010
-
In: Talanta. - : Elsevier BV. - 0039-9140. ; 81:4-5, s. 1153-1161
-
Journal article (peer-reviewed)abstract
- The aim of the present work is to develop a protocol for the specific immobilization of liposomes, via tethers, onto functionalized gold surfaces, and in addition to give one example for such a surface architecture All surface functionalization steps are charcerized and controlled First, mixed thiolate self-assembled monolayers (SAMs) prepared from COOH- and OCH3-terminated oligo(ethylene glycol) (OEG) alkane thiols were characterized by polarization modulation reflection absorption infrared spectroscopy (PM-RAIRS) and by X-ray photoemission spectroscopy (XPS). The composition of the mixed SAMs was found to be close to that of the thiol solution. Next, grafting of biotin conjugated with an NH2-terminated OEG spacer (biotin-OEG-NH2) to the COOH groups via conventional amine coupling was optimized with respect to the COOH/OCH3 ratio of the SAM. The grafting of biotin-OEG-NH2 was assessed by monitoring the binding of neutravidin and albumin to the biotinylated surfaces using quartz crystal microbalance with dissipation monitoring (QCM-D), as well as by PM-RAIRS It was shown that a COOH/OCH3 ratio of around 0.3 was sufficient to saturate the SAMs with neutravidin. Finally, tethering of liposomes onto the neutravidin-terminated SAMs. was achieved. As an application example. of a close packed layer of tethered liposomes was exposed to the membrane-penetrating peptide melittin As monitored by QCM-D. the liposomes fused when interacting with the peptide and ruptured into an extended. supported lipid bilayer over the whole surface. In summary, the described surface modification has potential for the development of assays requiring tethered Intact liposomes, or tethered planar bilayers. Such surface architectures are especially important for the study of transmembrane proteins and peptides.
|
|
| 12. |
- Briand, Elisabeth, 1979, et al.
(author)
-
Chemical Modifications of Au/SiO2 Template Substrates for Patterned Biofunctional Surfaces
- 2011
-
In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 27:2, s. 678-685
-
Journal article (peer-reviewed)abstract
- The aim of this work was to create patterned surfaces for localized and specific biochemical recognition. For this purpose, we have developed a protocol for orthogonal and material-selective surface modifications of microfabricated patterned surfaces composed of SiO2 areas (100 mu m diameter) surrounded by Au. The SiO2 spots were chemically modified by a sequence of reactions (silanization using an amine-terminated silane (APTES), followed by amine coupling of a biotin analogue and biospecific recognition) to achieve efficient immobilization of streptavidin in a functional form. The surrounding Au was rendered inert to protein adsorption by modification by HS(CH2)(10)CONH-(CH2)(2)(OCH2CH2)(7)OH (thiol-OEG). The surface modification protocol was developed by testing separately homogeneous SiO2 and Au surfaces, to obtain the two following results: (i) SiO2 surfaces which allowed the grafting of streptavidin, and subsequent immobilization of biotinylated antibodies, and (ii) Au surfaces showing almost no affinity for the same streptavidin and antibody solutions. The surface interactions were monitored by quartz crystal microbalance with dissipation monitoring (QCM-D), and chemical analyses were performed by polarization modulation-reflexion absorption infrared spectroscopy (PM-RAIRS) and X-ray photoelectron spectroscopy (XPS) to assess the validity of the initial orthogonal assembly of APTES and thiol-OEG. Eventually, microscopy imaging of the modified Au/SiO2 patterned substrates validated the specific binding of streptavidin on the SiO2/APTES areas, as well as the subsequent binding of biotinylated anti-rIgG and further detection of fluorescent rIgG on the functionalized SiO2 areas. These results demonstrate a successful protocol for the preparation of patterned biofunctional surfaces, based on microfabricated Au/SiO2 templates and supported by careful surface analysis. The strong immobilization of the biomolecules resulting from the described protocol is advantageous in particular for micropatterned substrates for cell-surface interactions.
|
|
| 13. |
- Briand, Elisabeth, 1979, et al.
(author)
-
Combined QCM-D and EIS study of supported lipid bilayer formation and interaction with pore-forming peptides
- 2010
-
In: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 135:2, s. 343-350
-
Journal article (peer-reviewed)abstract
- A novel set-up combining the quartz crystal microbalance with dissipation monitoring technique (QCM-D) and electrochemical impedance spectroscopy (EIS) under flow conditions was successfully used to follow supported lipid bilayer (SLB) formation on SiO(2). This study demonstrates the simultaneous detection, in real time, of both the electrical and the structural properties of the SLB. The combination of the two techniques provided novel insights regarding the mechanism of SLB formation: we found indications for an annealing process of the lipid alkyl chains after the mass corresponding to complete bilayer coverage had been deposited. Moreover, the interaction of the SLB with the pore-forming toxin, gramicidin D (grD) was studied for grD concentrations ranging from 0.05 to 40 mg L(-1). Membrane properties were altered depending on the toxin concentration. For low grD concentrations, the electrical properties of the SLB changed upon insertion of active ion channels. For higher concentrations, the QCM-D data showed dramatic changes in the viscoelastic properties of the membrane while the EIS spectra did not change. AFM confirmed significant structural changes of the membrane at higher grD concentrations. Thus, the application of combined QCM-D and EIS detection provides complementary information about the system under study. This information will be particularly important for the continued detailed investigation of interactions at model membrane surfaces
|
|
| 14. |
- Claesson, Maria, 1985, et al.
(author)
-
Pore Spanning Lipid Bilayers on Mesoporous Silica Having Varying Pore Size
- 2011
-
In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 27:14, s. 8974-8982
-
Journal article (peer-reviewed)abstract
- Synthetic lipid bilayers have similar properties as cell membranes and have been shown to be of great use in the development of novel biomimicry devices. In this study, lipid bilayer formation on mesoporous silica of varying pore size, 2, 4, and 6 nm, has been investigated using quartz crystal microbalance with dissipation monitoring (QCM-D), fluorescent recovery after photo bleaching (FRAP), and atomic force microscopy (AFM). The results show that pore-spanning lipid bilayers were successfully formed regardless of pore size. However, the mechanism of the bilayer formation was dependent on the pore size, and lower surface coverages of adsorbed lipid vesicles were required on the surface having the smallest pores. A similar trend was observed for the lateral diffusion coefficient (D) of fluorescently labeled lipid molecules in the membrane, which was lowest on the surface having the smallest pores and increased with the pore size. All of the pore size dependent observations are suggested to be due to the hydrophilicity of the surface, which decreases with increased pore size.
|
|
| 15. |
|
|
| 16. |
|
|
| 17. |
- Faxälv, Lars, et al.
(author)
-
Imaging of blood plasma coagulation at supported lipid membranes
- 2011
-
In: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 364:2, s. 582-587
-
Journal article (peer-reviewed)abstract
- The blood coagulation system relies on lipid membrane constituents to act as regulators of the coagulation process upon vascular trauma, and in particular the 2D configuration of the lipid membranes is known to efficiently catalyze enzymatic activity of blood coagulation factors. This work demonstrates a new application of a recently developed methodology to study blood coagulation at lipid membrane interfaces with the use of imaging technology. Lipid membranes with varied net charges were formed on silica supports by systematically using different combinations of lipids where neutral phosphocholine (PC) lipids were mixed with phospholipids having either positively charged ethylphosphocholine (EPC), or negatively charged phosphatidylserine (PS) headgroups. Coagulation imaging demonstrated that negatively charged SiO(2) and membrane surfaces exposing PS (obtained from liposomes containing 30% of PS) had coagulation times which were significantly shorter than those for plain PC membranes and EPC exposing membrane surfaces (obtained from liposomes containing 30% of EPC). Coagulation times decreased non-linearly with increasing negative surface charge for lipid membranes. A threshold value for shorter coagulation times was observed below a PS content of similar to 6%. We conclude that the lipid membranes on solid support studied with the imaging setup as presented in this study offers a flexible and non-expensive solution for coagulation studies at biological membranes. It will be interesting to extend the present study towards examining coagulation on more complex lipid-based model systems.
|
|
| 18. |
- Frost, Rickard, 1979, et al.
(author)
-
Acoustic detection of melanosome transport in Xenopus laevis melanophores
- 2013
-
In: Analytical Biochemistry. - : Elsevier BV. - 0003-2697 .- 1096-0309. ; 435:1, s. 10-18
-
Journal article (peer-reviewed)abstract
- Organelle transport studies are often performed using melanophores from lower vertebrates due to the ease of inducing movements of pigment granules (melanosomes) and visualizing them by optical microscopy. Here, we present a novel methodology to monitor melanosome translocation (which is a light-sensitive process) in the dark using the quartz crystal microbalance with dissipation monitoring (QCM-D) technique. This acoustic sensing method was used to study dispersion and aggregation of melanosomes in Xenopus laevis melanophores. Reversible sensor responses, correlated to optical reflectance measurements, were obtained by alternating addition and removal of melatonin (leading to melanosome aggregation) and melanocyte-stimulating hormone (MSH) (leading to melanosome dispersion). By confocal microscopy, it was shown that a vertical redistribution of melanosomes occurred during the dispersion/aggregation processes. Furthermore, the transport process was studied in the presence of cytoskeleton-perturbing agents disrupting either actin filaments (latrunculin) or microtubules (nocodazole). Taken together, these experiments suggest that the acoustic responses mainly originate from melanosome transport along actin filaments (located close to the cell membrane), as expected based on the penetration depth of the QCM-D technique. The results clearly indicate the potential of QCM-D for studies of intracellular transport processes in melanophores.
|
|
| 19. |
- Frost, Rickard, 1979, et al.
(author)
-
Bioreducible insulin-loaded nanoparticles and their interaction with model lipid membranes
- 2011
-
In: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 362:2, s. 575-583
-
Journal article (peer-reviewed)abstract
- To improve design processes in the field of nanomedicine, in vitro characterization of nanoparticles with systematically varied properties is of great importance. In this study, surface sensitive analytical techniques were used to evaluate the responsiveness of nano-sized drug-loaded polyelectrolyte complexes when adsorbed to model lipid membranes. Two bioreducible poly(amidoamine)s (PAAs) containing multiple disulfide linkages in the polymer backbone (SS-PAAs) were synthesized and used to form three types of nanocomplexes by self-assembly with human insulin, used as a negatively charged model protein at neutral pH. The resulting nanoparticles collapsed on top of negatively charged model membranes upon adsorption, without disrupting the membrane integrity. These structural rearrangements may occur at a cell surface which would prevent uptake of intact nanoparticles. By the addition of glutathione, the disulfide linkages in the polymer backbone of the SS-PAAs were reduced, resulting in fragmentation of the polymer and dissociation of the adsorbed nanoparticles from the membrane. A decrease in ambient pH also resulted in destabilization of the nanoparticles and desorption from the membrane. These mimics of intracellular environments suggest dissociation of the drug formulation, a process that releases the protein drug load, when the nanocomplexes reaches the interior of a cell. (C) 2011 Elsevier Inc. All rights reserved.
|
|
| 20. |
- Frost, Rickard, 1979, et al.
(author)
-
Characterization of nanoparticle-lipid membrane interactions using QCM-D
- 2013
-
In: Methods in Molecular Biology. - Totowa, NJ : Humana Press. - 1940-6029 .- 1064-3745. - 9781627033350 ; 991, s. 127-137
-
Book chapter (other academic/artistic)abstract
- In vitro characterization of nanoparticles is becoming increasingly important due to the rapid development of novel nanoparticle formulations for applications in the field of nanomedicine and related areas. Commonly, nanoparticles are simply characterized with respect to their size and zeta potential, and additional in vitro characterization of nanoparticles is needed to develop useful nanoparticle structure-activity relationships. In this context it is highly interesting to characterize the interactions between nanoparticles and model interfaces, such as lipid membranes. Here, we describe a methodology to study such interactions using the quartz crystal microbalance with dissipation monitoring technique (QCM-D). In order to mimic some aspects of the native cell membrane, a supported lipid membrane is formed on the QCM-D sensor surface. Subsequently the membrane is exposed to nanoparticles, and the nanoparticle-lipid membrane interactions are monitored in real time. The outcome of such analysis provides information on the adsorption process (importantly kinetics and adsorbed amounts) as well as on the integrity of both the nanoparticles and the lipid membrane upon interaction. QCM-D analyses are suitable for screening of nanoparticle-lipid membrane interactions due to the fair throughput of the technique, which can be complemented, when needed, by additional analyses by other surface-sensitive analytical techniques.
|
|
| 21. |
- Frost, Rickard, 1979, et al.
(author)
-
Core−Shell Nanoplasmonic Sensing for Characterization of Biocorona Formation and Nanoparticle Surface Interactions
- 2016
-
In: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 1:6, s. 798-806
-
Journal article (peer-reviewed)abstract
- Surface properties of nanoparticles imposed by particle size, shape, and surface chemistry are key features that largely determine their environmental fate and effects on biological systems. Consequently, development of analytical tools to characterize surface properties of nanomaterials and their relation to toxicological properties must occur in parallel with applications. As a contribution to this quest, we present a nanoplasmonic sensing strategy that enables systematic in situ characterization of molecule−nanoparticle interactions under well-controlled conditions, in terms of both nanoparticle size and surface chemistry, with particular focus on the importance of surface faceting in crystalline nanoparticles. We assess the performance of our sensing strategy by presenting two case studies. (i) The first is protein corona formation on faceted Au core−SiO2 shell nanoparticles of different sizes, and thus different surface facet-to-edge ratios. Based on 2D and 3D models of the investigated structures, we find that for small particles the curved regions between adjacent facets dominate the response of the corona formation process, whereas the facets dominate the response in the large particle regime. (ii) The second is in situ functionalization of Au core−SiO2 shell nanoparticle surfaces, and analysis of the subsequent protein repellent behavior. Due to the versatility of the presented sensing strategy in studies of nanoparticle surface properties, including in situ surface modifications, and their interactions with (bio)molecules during corona formation, we foresee it to become a valuable tool in the areas of nanomedicine and nanotoxicology.
|
|
| 22. |
- Frost, Rickard, 1979, et al.
(author)
-
Graphene Oxide and Lipid Membranes: Interactions and Nanocomposite Structures
- 2012
-
In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 12:7, s. 3356-3362
-
Journal article (peer-reviewed)abstract
- We have investigated the interaction between graphene oxide and lipid membranes, using both supported lipid membranes and supported liposomes. Also, the reverse situation, where a surface coated with graphene oxide was exposed to liposomes in solution, was studied. We discovered graphene oxide-induced rupture of preadsorbed liposomes and the formation of a nanocomposite, bio-nonbio multilayer structure, consisting of alternating graphene oxide monolayers and lipid membranes. The assembly process was monitored in real time by two complementary surface analytical techniques (the quartz crystal microbalance with dissipation monitoring technique (QCM-D) and dual polarization interferometry (DPI)), and the formed structures were imaged with atomic force microscopy (AFM). From a basic science point of view, the results point toward the importance of electrostatic interactions between graphene oxide and lipid headgroups. Implications from a more practical point of view concern structure activity relationship for biological health/safety aspects of graphene oxide and the potential of the nanocomposite, multilayer structure as scaffolds for advanced biomolecular functions and sensing applications.
|
|
| 23. |
- Frost, Rickard, 1979, et al.
(author)
-
Graphene Oxide and Lipid Membranes: Size-Dependent Interactions
- 2016
-
In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 32:11, s. 2708-2717
-
Journal article (peer-reviewed)abstract
- We have investigated the interaction of graphene oxide (GO) sheets with supported lipid membranes with focus on how the interaction depends on GO sheet size (three samples in the range of 90-5000 nm) and how it differs between small and large liposomes. The layer by-layer assembly of these materials into multilamellar structures, as discovered in our previous research, is now further explored. The interaction processes were monitored by two complementary, real time, surface-sensitive analytical techniques: quartz crystal microbalance with dissipation monitoring (QCM-D, electroacoustic sensing) and indirect nanoplasmonic sensing (INPS, optical sensing). The results show that the sizes of each of the two components, graphene oxide and liposomes, are important parameters affecting the resulting multilayer structures. Spontaneous liposome rupture onto graphene oxide is obtained for large lateral dimensions of the graphene oxide sheets.
|
|
| 24. |
|
|
| 25. |
|
|
| 26. |
|
|
| 27. |
- Frost, Rickard, 1979, et al.
(author)
-
Structural Rearrangements of Polymeric Insulin-loaded Nanoparticles Interacting with Surface-Supported Model Lipid Membranes
- 2011
-
In: Journal of Biomaterials and Nanobiotechnology. - 2158-7027. ; 2:2, s. 181-193
-
Journal article (peer-reviewed)abstract
- The design and screening of nanoparticles for therapeutic applications (nanodrugs) belong to an emerging research area, where surface based analytical techniques are promising tools. This study reports on the interaction of electro- statically assembled nanoparticles, developed for non-invasive administration of human insulin, with cell membrane mimics. Interactions between the nanoparticles and differently charged surface-supported model membranes were studied in real-time with the quartz crystal microbalance with dissipation monitoring (QCM-D) technique, in some ex- periments combined with optical reflectometry. Based on the experimental observations, we conclude that structural rearrangements of the nanoparticles occur upon adsorption to negatively charged lipid membranes.␣ The degree of structural changes in the nanoparticles will have important implications for the induced release of the protein drug load. The presented results provide an example of how a surface-based experimental platform can be used to charac- terize the physico-chemical properties of nanosized drug carriers with respect to their interactions at different surfaces.
|
|
| 28. |
- Gunnarsson, Anders, 1981, et al.
(author)
-
Kinetics of Ligand Binding to Membrane Receptors from Equilibrium Fluctuation Analysis of Single Binding Events
- 2011
-
In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 133:38, s. 14852-14855
-
Journal article (peer-reviewed)abstract
- Equilibrium fluctuation analysis of single binding events has been used to extract binding kinetics of ligand interactions with cell-membrane bound receptors. Time-dependent total internal reflection fluorescence (TIRF) imaging was used to extract residence-time statistics of fluorescently stained liposomes derived directly from cell membranes upon their binding to surface-immobilized antibody fragments. The dissociation rate constants for two pharmaceutical relevant antibodies directed against different B-cell expressed membrane proteins was clearly discriminated, and the affinity of the interaction could be determined by inhibiting the interaction with increasing concentrations of soluble antibodies. The single-molecule sensitivity made the analysis possible without overexpressed membrane proteins, which makes the assay attractive in early drug-screening applications.
|
|
| 29. |
- Höök, Fredrik, 1966, et al.
(author)
-
Supported lipid bilayers, tethered lipid vesicles, and vesicle fusion investigated using gravimetric, plasmonic, and microscopy techniques
- 2007
-
In: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 3:2
-
Journal article (peer-reviewed)abstract
- This article summarizes our most recent contributions to the rapidly growing field of supported lipid assemblies with emphasis on current studies addressing both fundamental and applied aspects of supported lipid bilayer (SLB) and tethered lipid vesicles (TLVs) to be utilized in sensing applications. The new insights obtained from combining the quartz crystal microbalance with dissipation monitoring technique with surface plasmon resonance are described, and we also present recent studies in which nanoplasmonic sensing has been used in studies of SLBs and TLVs. To gain full control over the spatial arrangement of TLVs in both two and three dimensions, we have developed a method for site-selective and sequence-specific sorting of DNA-tagged vesicles to surfaces modified with complementary DNA. The combination of this method with nanoplasmonic sensing formats is covered as well as the possibility of using DNA-modified vesicles for the detection of unlabeled DNA targets on the single-molecule level. Finally, a new method for membrane fusion induced by hybridization of vesicle-anchored DNA is demonstrated, including new results on content mixing obtained with vesicle populations encapsulating short, complementary DNA strands.
|
|
| 30. |
- Jing, Yujia, 1985, et al.
(author)
-
Asymmetric cationic liposomes designed for heat-activated association with cells
- 2017
-
In: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 151, s. 112-118
-
Journal article (peer-reviewed)abstract
- Improved anticancer drugs and drug carriers are needed in combination therapies, such as hyperthermia-assisted chemotherapy. Liposomal drug carriers with advanced functions are attractive candidates for targeted accumulation and drug release in response to heat stimulus. We report on the design of liposomes with a heat-activated surface function. Our design is based on asymmetric lipid membranes with a defined gel to liquid-crystalline phase-transition temperature around 41 °C. Asymmetry between the inner and the outer membrane leaflets was generated through selective PEGylation of cationic lipids in the outer membrane leaflet. In a physiological buffer, the PEGylated asymmetric liposomes had a neutral zeta potential and did not bind to planar anionic model membranes. In contrast, following upon heat-activation, binding of liposomes to the model membranes occurred. Release of a hydrophilic dye encapsulated in the asymmetric liposomes occurred at 40 °C. Enhanced uptake of the asymmetric liposomes by hypopharyngeal carcinoma cells (FaDu cells) was observed when hyperthermia was applied compared to experiments performed at 37 °C. These results show the potential of asymmetric liposomes for localized delivery of drugs into cells in response to (external) temperature stimulus.
|
|
| 31. |
- Jing, Yujia, 1985, et al.
(author)
-
Formation of supported lipid bilayers on silica: relation to lipid phase transition temperature and liposome size
- 2014
-
In: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 10:1, s. 187-195
-
Journal article (peer-reviewed)abstract
- DPPC liposomes ranging from 90 nm to 160 nm in diameter were prepared and used for studies of the formation of supported lipid membranes on silica (SiO2) at temperatures below and above the gel to liquid-crystalline phase transition temperature (T-m = 41 degrees C), and by applying temperature gradients through T-m. The main method was the quartz crystal microbalance with dissipation (QCM-D) technique. It was found that liposomes smaller than 100 nm spontaneously rupture on the silica surface when deposited at a temperature above T-m and at a critical surface coverage, following a well-established pathway. In contrast, DPPC liposomes larger than 160 nm do not rupture on the surface when adsorbed at 22 degrees C or at 50 degrees C. However, when liposomes of this size are first adsorbed at 22 degrees C and at a high enough surface coverage, after which they are subject to a constant temperature gradient up to 50 degrees C, they rupture and fuse to a bilayer, a process that is initiated around T-m. The results are discussed and interpreted considering a combination of effects derived from liposome-surface and liposome-liposome interactions, different softness/stiffness and shape of liposomes below and above T-m, the dynamics and thermal activation of the bilayers occurring around T-m and (for liposomes containing 33% of NaCl) osmotic pressure. These findings are valuable both for preparation of supported lipid bilayer cell membrane mimics and for designing temperature-responsive material coatings.
|
|
| 32. |
- Jing, Yujia, 1985, et al.
(author)
-
Heat-activated liposome targeting to streptavidin-coated surfaces
- 2015
-
In: Biochimica et Biophysica Acta - Biomembranes. - : Elsevier BV. - 1879-2642 .- 0005-2736. ; 1848:6, s. 1417-1423
-
Journal article (peer-reviewed)abstract
- There is a great need of improved anticancer drugs and corresponding drug carriers. In particular, liposomal drug carriers with heat-activated release and targeting functions are being developed for combined hyperthermia and chemotherapy treatments of tumors. The aim of this study is to demonstrate the heat-activation of liposome targeting to biotinylated surfaces, in model experiments where streptavidin is used as a pretargeting protein. The design of the heat-activated liposomes is based on liposomes assembled in an asymmetric structure and with a defined phase transition temperature. Asymmetry between the inside and the outside of the liposome membrane was generated through the enzymatic action of phospholipase D, where lipid head groups in the outer membrane leaflet, i.e. exposed to the enzyme, were hydrolyzed. The enzymatically treated and purified liposomes did not bind to streptavidin-modified surfaces. When activation heat was applied, starting from 22 degrees C, binding of the liposomes occurred once the temperature approached 33 +/- 0.5 degrees C. Moreover, it was observed that the asymmetric structure remained stable for at least 2 weeks. These results show the potential of asymmetric liposomes for the targeted binding to cell membranes in response to (external) temperature stimulus. By using pretargeting proteins, this approach can be further developed for personalized medicine, where tumor-specific antibodies can be selected for the conjugation of pretargeting agents.
|
|
| 33. |
- Jing, Yujia, 1985, et al.
(author)
-
Phase Transition-Controlled Flip-Flop in Asymmetric Lipid Membranes
- 2014
-
In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 118:9, s. 2389-2395
-
Journal article (peer-reviewed)abstract
- Lipid membrane asymmetry is of fundamental importance for biological systems and also provides an attractive means for molecular control over biomaterial surface properties (including drug carriers). In particular, temperature-dependent changes of surface properties can be achieved by taking advantage of distinct phase transitions in lipid membrane coatings where lipids exchange (flip-flop) between leaflets. In this study, temperature is used to control flip-flop of lipids in asymmetric lipid membranes on planar solid supports, where the two leaflets of the lipid membrane are in different phase states. More specifically, the lower leaflet is prepared from a supported lipid membrane composed of a high T-m lipid mixture of phosphocholine (PC), phosphatidylserine (PS), and a bioactive lipid on TiO2, followed by selective removal of the top leaflet by detergent. Next, at a lower temperature, where the remaining leaflet is in the gel state, a top leaflet of a different lipid composition and in the fluid phase is formed. Phase transition-induced changes in membrane surface properties following upon temperature-activation of the prepared asymmetric membrane are demonstrated by the detection of biotinylated lipids, which were initially located (thus "hidden") in the lower-gel phase leaflet, at the surface of the top leaflet. These processes were monitored in real-time by the quartz crystal microbalance with dissipation (QCM-D) and the dual polarization interferometry (DPI) techniques, allowing modeling of the mass and the anisotropic property of the lipid structures in different phase states.
|
|
| 34. |
- Karlsson, Hanna, et al.
(author)
-
Cell membrane damage and protein interaction induced by copper containing nanoparticles-Importance of the metal release process
- 2013
-
In: Toxicology. - : Elsevier BV. - 0300-483X .- 1879-3185. ; 313:1, s. 59-69
-
Journal article (peer-reviewed)abstract
- Cu-containing nanoparticles are used in various applications in order to e.g. achieve antimicrobial activities and to increase the conductivity of fluids and polymers. Several studies have reported on toxic effects of such particles but the mechanisms are not completely clear. The aim of this study was to investigate the interactions between cell membranes and well-characterized nanoparticles of CuO, Cu metal, a binary Cu-Zn alloy and micron-sized Cu metal particles. This was conducted via in vitro investigations of the effects of the nanoparticles on (i) cell membrane damage on lung epithelial cells (A549), (ii) membrane rupture of red blood cells (hemolysis), complemented by (iii) nanoparticle interaction studies with a model lipid membrane using quartz crystal microbalance with dissipation monitoring (QCM-D). The results revealed that nanoparticles of the Cu metal and the Cu-Zn alloy were both highly membrane damaging and caused a rapid (within 1 h) increase in membrane damage at a particle mass dose of 20 mu g/mL, whereas the CuO nanoparticles and the micron-sized Cu metal particles showed no such effect. At similar nanoparticle surface area doses, the nano and micron-sized Cu particles showed more similar effects. The commonly used LDH (lactate dehydrogenase) assay for analysis of membrane damage was found impossible to use due to nanoparticle-assay interactions. None of the particles induced any hemolytic effects on red blood cells when investigated up to high particle concentrations (1 mg/mL). However, both Cu and Cu-Zn nanopartides caused hemoglobin aggregation/precipitation, a process that would conceal a possible hemolytic effect. Studies on interactions between the nanoparticles and a model membrane using QCM-D indicated a small difference between the investigated particles. Results of this study suggest that the observed membrane damage is caused by the metal release process at the cell membrane surface and highlight differences in reactivity between metallic nanoparticles of Cu and Cu-Zn and nanoparticles of CuO.
|
|
| 35. |
- Kunze, Angelika, 1978, et al.
(author)
-
Electrodeless QCM-D for lipid bilayer applications
- 2011
-
In: Biosensors and Bioelectronics. - : Elsevier BV. - 0956-5663 .- 1873-4235. ; 26:5, s. 1833-1838
-
Journal article (peer-reviewed)abstract
- An electrodeless quartz crystal microbalance with dissipation monitoring (QCM-D) setup is used to monitor the formation of supported lipid bilayers (SLBs) on bare quartz crystal sensor surfaces. The kinetic behavior of the formation of a 1-palmitoyl-2-oleoyl-sn-glycero-3-Phosphocholine (POPC) SLB on SiO2 surfaces is discussed and compared for three cases: (i) a standard SiO2 film deposited onto the gold electrode of a quartz crystal, (ii) an electrodeless quartz crystal with a sputter-coated SiO2 film, and (iii) an uncoated electrodeless quartz crystal sensor surface. We demonstrate, supported by imaging the SLB on an uncoated electrodeless surface using atomic force microscopy (AFM), that a defect-free, completely covering bilayer is formed in all three cases. Differences in the kinetics of the SLB formation on the different sensor surfaces are attributed to differences in surface roughness. The latter assumption is supported by imaging the different surfaces using AFM. We show furthermore that electrodeless quartz crystal sensors can be used not only for the formation of neutral SLBs but also for positively and negatively charged SLBs. Based on our results we propose electrodeless QCM-D to be a valuable technique for lipid bilayer and related applications providing several advantages compared to electrode-coated surfaces like optical transparency, longer lifetime, and reduced costs.
|
|
| 36. |
- Kunze, Angelika, 1978, et al.
(author)
-
In situ preparation and modification of supported lipid layers by lipid transfer from vesicles studied by QCM-D and TOF-SIMS
- 2009
-
In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 131:7, s. 2450-2451
-
Journal article (peer-reviewed)abstract
- The study of lipid transfer between lipid membranes is of great interest for the fundamental understanding of this complex and important process and, furthermore, for providing a new avenue for the in situ modification of supported lipid bilayers (SLBs). SLBs are conveniently formed by vesicle spreading onto a solid support, but this method is limited to conditions (i.e., combination of vesicle lipid composition, surface chemical properties, and buffer) such that the vesicles break spontaneously upon adsorption to the surface. Many SLB compositions are not accessible by this approach. In the present study, we give an example of how lipid transfer can be made use of to form lipid layers with striking new features, notably with respect to stability. After lipid transfer between negatively charged POPS small unilamellar vesicles and a positively charged POEPC SLB on TiO2, an SLB is obtained, which, upon exposure to SDS, leaves behind a lipid monolayer. It is shown how this monolayer can be used for creating new SLBs. The several step procedure, bilayer formation, lipid transfer, removal of a lipid monolayer and the reassembly of a bilayer, is monitored in real time by the quartz crystal microbalance with a dissipation (QCM-D) technique, and the lipid composition is analyzed for each step in postpreparation spectroscopic analyses using time-of-flight secondary ion mass spectrometry (TOF-SIMS). Comparison of the measured signal ratios with those of the reference samples containing known fractions of D31-POPS directly shows that the relative concentration of D31-POPS is 50% in the SLB after D31-POPS exchange, significantly higher in the monolayer prepared in situ by SDS rinse, and 20-25% after reassembly of the SLB using POEPC vesicles. The results thus provide unambiguous evidence for extensive lipid transfer between the initial POEPC SLB and D31-POPS vesicles in solution. We suggest that the reassembled SLB has a significant asymmetry between the two leaflets, and we propose that the described method is promising for the in situ preparation of asymmetric SLBs.
|
|
| 37. |
- Kunze, Angelika, 1978, et al.
(author)
-
Ion-mediated changes of supported lipid bilayers and their coupling to the substrate. A case of bilayer slip?
- 2011
-
In: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 7:18, s. 8582-8591
-
Journal article (peer-reviewed)abstract
- Ion-mediated (Ca(2+)) changes in viscoelastic, structural and optical properties of negatively charged solid supported lipid bilayers (SLBs) on SiO(2) surfaces were studied by means of quartz crystal microbalance with dissipation (QCM-D) monitoring and optical reflectometry. Despite the sensitivity of QCM-D to viscoeleastic/structural variations, it has not often been used to probe such changes for SLBs. SLBs were prepared from binary phospholipid mixtures of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC, neutral) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (POPG, negatively charged) on SiO(2) sensor surfaces in a Ca(2+)-containing buffer. Interestingly, for bilayers containing POPG fractions above 35%, large QCM-D dissipation shifts occurred, when Ca(2+) was removed from buffer in contact with the SLB (while maintaining 100 mM NaCl). The accompanying frequency changes were small. These Ca(2+) mediated QCM-D responses are reversible, and a signal for considerable changes in the viscoelastic and structural properties of the SLB. Variation of Ca(2+)-concentration revealed a threshold concentration of around 0.4 mM for the changes in the SLB to occur. Below this value, at >35% POPG concentration in the SLB, the SLB appears to become more weakly attached to the SiO(2) substrate, which is partly attributed to a weakening of the POPG-substrate interaction in the absence of Ca(2+). A consequence of this is an oscillation-amplitude dependent dissipation, which we attribute to slip of the bilayer at higher oscillation amplitudes. Complementary experiments using a combined QCM-D/reflectometry instrument showed that the Ca(2+)-induced changes in the viscoelastic/structural properties of the SLB are accompanied by changes in the optical properties. We discuss different scenarios to explain the observed reversible effect of Ca(2+)-ions on the dissipative and optical properties of the mixed SLBs. Based on our results we propose the observed phenomenon to be a combination of geometric changes, internal structural changes, changes in the interfacial water layer, and a slip mechanism, i.e. friction between the SLB and the substrate.
|
|
| 38. |
|
|
| 39. |
- Kunze, Angelika, 1978, et al.
(author)
-
Non-Invasive Acoustical sensing of Drug-Induced Effects on the Contractile Machinery of Human Cardiomyocyte Clusters
- 2015
-
In: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 10:5, s. 1-10
-
Journal article (peer-reviewed)abstract
- There is an urgent need for improved models for cardiotoxicity testing. Here we propose acoustic sensing applied to beating human cardiomyocyte clusters for non-invasive, surrogate measuring of the QT interval and other characteristics of the contractile machinery. In experiments with the acoustic method quartz crystal microbalance with dissipation monitoring (QCM-D), the shape of the recorded signals was very similar to the extracellular field potential detected in electrochemical experiments, and the expected changes of the QT interval in response to addition of conventional drugs (E-4031 or nifedipine) were observed. Additionally, changes in the dissipation signal upon addition of cytochalasin D were in good agreement with the known, corresponding shortening of the contraction-relaxation time. These findings suggest that QCM-D has great potential as a tool for cardiotoxicological screening, where effects of compounds on the cardiomyocyte contractile machinery can be detected independently of whether the extracellular field potential is altered or not.
|
|
| 40. |
- Kunze, Angelika, 1978, et al.
(author)
-
Real-time monitoring of surface-confined platelet activation on TiO2
- 2014
-
In: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 116, s. 446-451
-
Journal article (peer-reviewed)abstract
- For the development of advanced hemocompatible biomaterial functions, there is an unmet demand for in vitro evaluation techniques addressing platelet-surface interactions. We show that the quartz crystal microbalance with dissipation (QCM-D) monitoring technique, here combined with light microscopy, provides a surface sensitive technique that allows for real-time monitoring of the activation and aggregation of the surface-confined platelets on TiO2. The QCM-D signal monitored during adhesion and activation of platelets on TiO2 coated surfaces was found to be different in platelet-poor and platelet-rich environment although light microscopy images taken for each of the two cases looked essentially the same. Interestingly, aggregation of activated platelets was only observed in a protein-rich environment. Our results show that a layer of plasma proteins between the TiO2 surface and the platelets strongly influences the coupling between the platelets and the underlying substrate, explaining both the observed QCM-D signals and the ability of the platelets to aggregate. © 2014 The Authors.
|
|
| 41. |
- Nilebäck, Erik, 1984, et al.
(author)
-
Acoustic monitoring of changes in well-defined hyaluronan layers exposed to chondrocytes
- 2014
-
In: Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 139:21, s. 5350-5353
-
Journal article (peer-reviewed)abstract
- The interaction of human-derived chondrocytes and thin hyaluronan layers was studied using the quartz crystal microbalance with dissipation (QCM-D) technique combined with light microscopy. This approach allowed unique real-time monitoring of the interface between the cells and the sensor surface. Our results suggest that the hyaluronan layer is rapidly degraded by chondrocytes.
|
|
| 42. |
- Nilebäck, Erik, 1984, et al.
(author)
-
Characterization and application of a surface modification designed for QCM-D studies of biotinylated biomolecules
- 2011
-
In: Biosensors and Bioelectronics. - : Elsevier BV. - 0956-5663 .- 1873-4235. ; 28:1, s. 407-413
-
Journal article (peer-reviewed)abstract
- The rapid development of surface sensitive biosensor technologies, especially towards nanoscale devices, requires increasing control of surface chemistry to provide reliable and reproducible results, but also to take full advantage of the sensing opportunities. Here, we present a surface modification strategy to allow biotinylated biomolecules to be immobilized to gold coated sensor crystals for quartz crystal microbalance with dissipation monitoring (QCM-D) sensing. The unique feature of QCM-D is its sensitivity to nanomechanical (viscoelastic) properties at the sensing interface. The surface modification was based on mixed monolayers of oligo(ethylene glycol) (OEG) disulfides, with terminal -OH or biotin groups, on gold. Mixtures containing 1% of the biotin disulfide were concluded to be the most appropriate based on the performance when streptavidin was immobilized to biotinylated sensors and the subsequent biotinylated bovine serum albumin (BSA) interaction was studied. The OEG background kept the unspecific protein binding to a minimum, even when subjected to serum solutions with a high protein concentration. Based on characterization by contact angle goniometry, ellipsometry, and infrared spectroscopy, the monolayers were shown to be well-ordered, with the OEG chains predominantly adopting a helical conformation but also partly an amorphous structure. Storage stability was concluded to depend mainly on light exposure while almost all streptavidin binding activity was retained when storing the sensors cold and dark for 8 weeks. The surface modification was also tested for repeated antibody-antigen interactions between BSA and anti-BSA (immobilized to biotinylated protein A) in QCM-D measurements lasting for >10 h with intermediate basic regeneration. This proved an excellent stability of the coating and good reproducibility was obtained for 5 interaction cycles. With this kind of generic surface modification QCM-D can be used in a variety of biosensing applications to provide not only mass but also relevant information of the structural properties of adlayers.
|
|
| 43. |
|
|
| 44. |
- Nilebäck, Erik, 1984, et al.
(author)
-
Viscoelastic Sensing of Conformational Changes in Plasminogen Induced upon Binding of Low Molecular Weight Compounds
- 2010
-
In: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 82:20, s. 8374-8376
-
Journal article (peer-reviewed)abstract
- Plasminogen is a precursor to the fibrinolytic enzyme plasmin and is known to undergo large conformational changes when subjected to low molecular lysine analogues such as tranexamic acid (TA) or epsilon-amino-n-caproic acid (EACA). Here, we demonstrate how well-controlled surface immobilization of biotinylated plasminogen allows for monitoring of the interaction between TA and EACA with plasminogen. The interaction was studied by the quartz crystal microbalance with dissipation monitoring (QCM-D) technique as well as by surface plasmon resonance (SPR) based sensing. QCM-D measures changes in acoustically coupled mass (by detection of changes in the resonance frequency of the crystal, Delta f) and is sensitive to changes in mass adsorbed on the sensor surface including how liquid medium is associated with this material. Through the dissipation factor (i.e., changes in the energy dissipation of the crystal oscillation, Delta D), QCM-D is also sensitive to the viscoelastic properties of material adsorbed to the sensor surface. Upon binding of TA or EACA, changes in the plasminogen structure were recorded as distinct, although small, Delta D responses which were used to determine affinity constants. By comparing native and truncated plasminogen, we conclude that the observed dissipation shifts were caused by conformational changes in the proteins leading to changes in the viscoelastic properties of the protein layer on the surface. These results demonstrate a novel application of the QCM-D technique, paving the way for a whole new approach to screening of this target for novel lead structures.
|
|
| 45. |
- Ohlsson, Gabriel, 1982, et al.
(author)
-
A miniaturized flow reaction chamber for use in combination with QCM-D sensing
- 2010
-
In: Microfluidics and Nanofluidics. - : Springer Science and Business Media LLC. - 1613-4990 .- 1613-4982. ; 9:4-5, s. 705-716
-
Journal article (peer-reviewed)abstract
- A miniaturized flow chamber for quartz crystal microbalance with dissipation monitoring (QCM-D) has been developed. The main purpose was to reduce the total liquid sample consumption during an experiment, but also to gain advantages with respect to kinetics and mass transport by reducing the boundary diffusion layer. The bottom of the flow chamber is a QCM-D sensor surface, on which a polydimethylsiloxane spacer ring, fabricated onto a poly(methyl methacrylate) lid, is placed symmetrically around the QCM-D electrode (diameter similar to 10 mm). The spacer ring defines the inner chamber height (typically 40-50 mu m) and provides sealing. Through the lid, there are inlet and outlet channels. The typical chamber volume is in the range of 2.5-3.5 mu l (with a 10 mu l dead volume). In flow mode, we have operated the cell at flow rates of 6-50 mu l/min, i.e., volume turnovers of 2-17 per min. As a model system, to test the microcell, the formation of supported phospholipid bilayers on a SiO2 surface was studied. For comparison, the same process was studied in a commercially available QCM-D equipment with significantly larger total volume (by a factor of 20). The decrease in effective sample consumption to produce a bilayer on the sensor surface in the chamber was approximately proportional to the decrease in chamber volume. Smaller volume also reduced the liquid exchange time. Potential improvements of the chamber include further optimization of the flow profile and, in addition, further miniaturization by decreasing the chamber height and the sensor radius.
|
|
| 46. |
|
|
| 47. |
- Rydberg, Hanna, 1982, et al.
(author)
-
Peptide-membrane interactions of arginine-tryptophan peptides probed using quartz crystal microbalance with dissipation monitoring
- 2014
-
In: European Biophysics Journal. - : Springer Science and Business Media LLC. - 1432-1017 .- 0175-7571. ; 43:6-7, s. 241-253
-
Journal article (peer-reviewed)abstract
- Membrane-active peptides include peptides that can cross cellular membranes and deliver macromolecular cargo as well as peptides that inhibit bacterial growth. Some of these peptides can act as both transporters and antibacterial agents. It is desirable to combine the knowledge from these two different fields of membrane-active peptides into design of new peptides with tailored actions, as transporters of cargo or as antibacterial substances, targeting specific membranes. We have previously shown that the position of the amino acid tryptophan in the peptide sequence of three arginine-tryptophan peptides affects their uptake and intracellular localization in live mammalian cells, as well as their ability to inhibit bacterial growth. Here, we use quartz crystal microbalance with dissipation monitoring to assess the induced changes caused by binding of the three peptides to supported model membranes composed of POPC, POPC/POPG, POPC/POPG/cholesterol or POPC/lactosyl PE. Our results indicate that the tryptophan position in the peptide sequence affects the way these peptides interact with the different model membranes and that the presence of cholesterol in particular seems to affect the membrane interaction of the peptide with an even distribution of tryptophans in the peptide sequence. These results give mechanistic insight into the function of these peptides and may aid in the design of membrane-active peptides with specified cellular targets and actions.
|
|
| 48. |
- Satriano, Cristina, et al.
(author)
-
Plasma oxidized polyhydroxymethylsiloxane – a new smooth surface for supported lipid bilayer formation
- 2010
-
In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 26:8, s. 5715-5725
-
Journal article (peer-reviewed)abstract
- A novel substrate For preparation of supported lipid bilayers (SLBs), smooth at the subnanometer scale and of variable thickness from ten to several hundred nanometers, was developed by surface oxidation at spin-coated poly(hydroxymethylsiloxane) (PHMS) films. The deposited polymeric thin films were modified by a combination of oxygen plasma and thermal treatment (PHMS(ox)), in order to convert the outermost surface layer of the polymer film to a stable SiO(2) film, suitable for SLB formation. The hydrophilic, SiO(2)-like surfaces were characterized by XPS, wetting angle, ellipsometry, and AFM. Lipid bilayers were formed on this surface using the well-known vesicle adsorption-rupture-fusion process, usually performed on glass or vapor-deposited SiO(2). Reproducible formation of homogeneous SLBs of different compositions (POPC. DOEPC. and POPC/DOPS) was demonstrated on the new SiO(2) surface by quartz crystal microbalance with dissipation (QCM-D), surface plasmon resonance (S PR), and optical reflectometry measurements. The SLB formation kinetics on the PHMS(ox)-coated sensors showed very similar characteristics, for all investigated PHMS thicknesses, as on reference sensors coated with vapor-deposited SiO(2). The good adhesive properties of the PHMS to gold allows for the preparation of thin PHMS(ox) layers compatible with SPR. The much smaller roughness at the nanometer scale of the PHMS(ox) surfaces, compared to standard vapor-deposited SiO(2)-coated sensors, makes them advantageous for AFM and optical experiments and promising for patterning. To benefit optical experiments with the PHMS(ox) surfaces, it was also investigated how the PHMS film thickness influences the SPR and reflectometry responses upon SLB formation.
|
|
| 49. |
- Satriano, Cristina, et al.
(author)
-
Well-defined lipid interfaces for protein adsorption studies
- 2012
-
In: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 14:48, s. 16695-16698
-
Journal article (peer-reviewed)abstract
- The biomolecule-artificial lipid membrane interface has been investigated by QCM-D, SPR, and FRAP techniques, to study the adsorption process of ferritin on supported lipid bilayers (SLBs) of different composition and charge. Results point to the predominant role of electrostatics in triggering the interaction of ferritin with SLBs.
|
|
| 50. |
- Sun, Lu, 1982, et al.
(author)
-
Construction and Modeling of Concatemeric DNA Multilayers on a Planar Surface as Monitored by QCM-D and SPR
- 2014
-
In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 30:28, s. 8432-8441
-
Journal article (peer-reviewed)abstract
- The sequential hybridization of a 534 base pair DNA concatemer layer was monitored by QCM-D and SPR, and the QCM-D data were analyzed by Voigt viscoelastic models. The results show that Voigt-based modeling gives a good description of the experimental data but only if shear viscosity and elasticity are allowed to depend on the shear frequency. The derived layer thickness, shear viscosity and elasticity of the growing film give a representation of the DNA film in agreement with known bulk properties of DNA, and reveal a maximum in film viscosity when the molecules in the layer contain 75 base pairs. The experimental data during construction of a 3084 bp DNA concatemer layer were compared to predictions of the QCM-D response of a 1 mu m thick film of rod-like polymers. A predicted nonmonotonous variation of dissipation with frequency (added mass) is in qualitative agreement with the experiments, but with a quantitative disagreement which likely reflects that the flexibility of such long DNA molecules is not included in the model.
|
|
