| 1. |
- Caselli, Lucrezia, et al.
(författare)
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Boosting Membrane Interactions and Antimicrobial Effects of Photocatalytic Titanium Dioxide Nanoparticles by Peptide Coating
- 2024
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Ingår i: Small. - : John Wiley and Sons Inc. - 1613-6810 .- 1613-6829.
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Tidskriftsartikel (refereegranskat)abstract
- Photocatalytic nanoparticles offer antimicrobial effects under illumination due to the formation of reactive oxygen species (ROS), capable of degrading bacterial membranes. ROS may, however, also degrade human cell membranes and trigger toxicity. Since antimicrobial peptides (AMPs) may display excellent selectivity between human cells and bacteria, these may offer opportunities to effectively “target” nanoparticles to bacterial membranes for increased selectivity. Investigating this, photocatalytic TiO2 nanoparticles (NPs) are coated with the AMP LL-37, and ROS generation is found by C11-BODIPY to be essentially unaffected after AMP coating. Furthermore, peptide-coated TiO2 NPs retain their positive ζ-potential also after 1–2 h of UV illumination, showing peptide degradation to be sufficiently limited to allow peptide-mediated targeting. In line with this, quartz crystal microbalance measurements show peptide coating to promote membrane binding of TiO2 NPs, particularly so for bacteria-like anionic and cholesterol-void membranes. As a result, membrane degradation during illumination is strongly promoted for such membranes, but not so for mammalian-like membranes. The mechanisms of these effects are elucidated by neutron reflectometry. Analogously, LL-37 coating promoted membrane rupture by TiO2 NPs for Gram-negative and Gram-positive bacteria, but not for human monocytes. These findings demonstrate that AMP coating may selectively boost the antimicrobial effects of photocatalytic NPs. © 2024 The Authors.
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| 2. |
- Dabkowska, Aleksandra P., et al.
(författare)
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Non-lamellar lipid assembly at interfaces : controlling layer structure by responsive nanogel particles
- 2017
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Ingår i: Interface Focus. - : ROYAL SOC. - 2042-8898 .- 2042-8901. ; 7:4
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Tidskriftsartikel (refereegranskat)abstract
- Biological membranes do not only occur as planar bilayer structures, but depending on the lipid composition, can also curve into intriguing three-dimensional structures. In order to fully understand the biological implications as well as to reveal the full potential for applications, e.g. for drug delivery and other biomedical devices, of such structures, well-defined model systems are required. Here, we discuss the formation of lipid non-lamellar liquid crystalline (LC) surface layers spin-coated from the constituting lipids followed by hydration of the lipid layer. We demonstrate that hybrid lipid polymer films can be formed with different properties compared with the neat lipid LC layers. The nanostructure and morphologies of the lipid films formed reflect those in the bulk. Most notably, mixed lipid layers, which are composed of glycerol monooleate and diglycerol monooleate with poly(N-isopropylacrylamide) nanogels, can form films of reverse cubic phases that are capable of responding to temperature stimulus. Owing to the presence of the nanogel particles, changing the temperature not only regulates the hydration of the cubic phase lipid films, but also the lateral organization of the lipid domains within the lipid self-assembled film. This opens up the possibility for new nanostructured materials based on lipid-polymer responsive layers.
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| 3. |
- Del Giudice, Alessandra, et al.
(författare)
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Towards natural care products : Structural and deposition studies of bio-based polymer and surfactant mixtures
- 2024
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - 0927-7757. ; 698
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Tidskriftsartikel (refereegranskat)abstract
- Oppositely charged polymer-surfactant systems are expected to interact with formation of coacervate complexes near composition of charge-neutrality. Such behaviour is widely used in formulated products (e.g. household and personal care), where the co-deposition of coacervates and active ingredients on various surfaces is triggered by dilution. A transition towards the use of more sustainable ingredients is currently ongoing as a response to the need of more environmentally conscious choices in production, albeit slowed down by the often more complex and not fully understood bulk and interfacial behaviour of new ingredients. In this work, mixtures of a medium-chain fatty acid (sodium decanoate) and two grades of bio-based cationic modified inulin were studied. The phase behaviour was determined in a wide composition matrix. The formation of coacervate complexes was observed for the mixture with the higher charge density polymer at a surfactant concentration of 1–3 wt%, close to the surfactant critical micellar concentration in pure water. Such behaviour was confirmed by DLS and SAXS data, suggesting surfactant-polymer complexation in a concentrated phase of packed micelles with a micelle-to-micelle distance of ∼4.5 nm. In situ ellipsometry and neutron reflectometry experiments were conducted to study the effect on surface deposition when diluting. The ellipsometry showed an adsorbed mass of ∼1.3–1.9 mg/m2, consistent with the deposition of a coacervate layer, and considerably higher than the neat, adsorbed polymer layer of ∼0.3 mg/m2. In the case of the neutron reflectometry experiments, dilution was performed before contact with the surface (pre-mixing), and no adsorption of coacervates was observed, but rather the adsorption of a polymer layer (0.49–0.85 mg/m2). The different results obtained with the different techniques highlight the kinetic nature of bulk coacervate formation and deposition, and the competition between these two phenomena. Maximal deposition can be achieved if one can control this time window either by tuning the composition of the system or the experimental set-up, to mimic the conditions of a specific application.
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| 4. |
- Gilbert, Jennifer, et al.
(författare)
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On the interactions between RNA and titrateable lipid layers: implications for RNA delivery with lipid nanoparticles
- 2023
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Ingår i: Nanoscale. - 2040-3372 .- 2040-3364. ; 16:2, s. 777-794
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Tidskriftsartikel (refereegranskat)abstract
- Characterising the interaction between cationic ionisable lipids (CIL) and nucleic acids (NAs) is key to understanding the process of RNA lipid nanoparticle (LNP) formation and release of NAs from LNPs. Here, we have used different surface techniques to reveal the effect of pH and NA type on the interaction with a model system of DOPC and the CIL DLin-MC3-DMA (MC3). At only 5% MC3, differences in the structure and dynamics of the lipid layer were observed. Both pH and %MC3 were shown to affect the absorption behaviour of erythropoietin mRNA, polyadenylic acid (polyA) and polyuridylic acid (polyU). The adsorbed amount of all studied NAs was found to increase with decreasing pH and increasing %MC3 but with different effects on the lipid layer, which could be linked to the NA secondary structure. For polyA at pH 6, adsorption to the surface of the layer was observed, whereas for other conditions and NAs, penetration of the NA into the layer resulted in the formation of a multilayer structure. By comparison to simulations excluding the secondary structure, differences in adsorption behaviours between polyA and polyU could be observed, indicating that the NA's secondary structure also affected the MC3-NA interactions.
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| 5. |
- Hemming, Joanna M., et al.
(författare)
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Changes to lung surfactant monolayers upon exposure to gas phase ozone observed using X-ray and neutron reflectivity
- 2022
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Ingår i: Environmental Science. - : Royal Society of Chemistry. - 2634-3606. ; 2:4, s. 753-760
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Tidskriftsartikel (refereegranskat)abstract
- Exposure to the secondary pollutant ozone in ambient air is associated with adverse health effects when inhaled. In this work we use surface pressure measurements, combined with X-ray and neutron reflection, to observe changes in a layer of lung surfactant at the air water interface when exposed to gas phase ozone. The results demonstrate that the layer reacts with ozone changing its physical characteristics. A slight loss of material, a significant thinning of the layer and increased hydration of the surfactant material is observed. The results support the hypothesis that unsaturated lipids present in lung surfactant are still susceptible to rapid reaction with ozone and the reaction changes the properties of the interfacial layer.
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| 6. |
- Häffner, Sara Malekkhaiat, et al.
(författare)
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Membrane Interactions of Virus-like Mesoporous Silica Nanoparticles
- 2021
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 15:4, s. 6787-6800
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, we investigated lipid membrane interactions of silica nanoparticles as carriers for the antimicrobial peptide LL-37 (LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES). In doing so, smooth mesoporous nanoparticles were compared to virus-like mesoporous nanoparticles, characterized by a "spiky"external surface, as well as to nonporous silica nanoparticles. For this, we employed a combination of neutron reflectometry, ellipsometry, dynamic light scattering, and ζ-potential measurements for studies of bacteria-mimicking bilayers formed by palmitoyloleoylphosphatidylcholine/palmitoyloleoylphosphatidylglycerol. The results show that nanoparticle topography strongly influences membrane binding and destabilization. We found that virus-like particles are able to destabilize such lipid membranes, whereas the corresponding smooth silica nanoparticles are not. This effect of particle spikes becomes further accentuated after loading of such particles with LL-37. Thus, peptide-loaded virus-like nanoparticles displayed more pronounced membrane disruption than either peptide-loaded smooth nanoparticles or free LL-37. The structural basis of this was clarified by neutron reflectometry, demonstrating that the virus-like nanoparticles induce trans-membrane defects and promote incorporation of LL-37 throughout both bilayer leaflets. The relevance of such effects of particle spikes for bacterial membrane rupture was further demonstrated by confocal microscopy and live/dead assays on Escherichia coli bacteria. Taken together, these findings demonstrate that topography influences the interaction of nanoparticles with bacteria-mimicking lipid bilayers, both in the absence and presence of antimicrobial peptides, as well as with bacteria. The results also identify virus-like mesoporous nanoparticles as being of interest in the design of nanoparticles as delivery systems for antimicrobial peptides.
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| 7. |
- Kamata, Yohei, et al.
(författare)
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Hydration and Ordering of Lamellar Block Copolymer Films under Controlled Water Vapor
- 2014
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 47:24, s. 8682-8690
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Tidskriftsartikel (refereegranskat)abstract
- Amphiphilic block copolymers within a range of volume fraction spontaneously form vesicles in aqueous solution, where a water core is enclosed by a polymer bilayer. Thin-film rehydration is a method used to produce vesicles routinely; a thin film is immersed in water, the film swells, and vesicles are formed which bleb off from the film surface. We have studied the early stages of hydration for PEOPBO block copolymer thin films under controlled water vapor conditions to understand this formation mechanism and so enable more efficient ways to encapsulate molecules using this method. Neutron and X-ray measurements show that the initial film exhibits weakly ordered structure with isotropic parallel and vertical orientation; the films initially swell and maintain the same orientation. At a critical point the layer swells rapidly and makes highly ordered lamellae structure at the same time. The lamellae are almost exclusively oriented parallel to the substrate and swell with increasing water absorption.
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| 8. |
- Lind, Tania Kjellerup, et al.
(författare)
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Formation and Characterization of Supported Lipid Bilayers Composed of Phosphatidylethanolamine and Phosphatidylglycerol by Vesicle Fusion, a Simple but Relevant Model for Bacterial Membranes
- 2019
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 4:6, s. 10687-10694
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Tidskriftsartikel (refereegranskat)abstract
- Supported lipid bilayers (SLBs) are simple and robust biomimics with controlled lipid composition that are widely used as models of both mammalian and bacterial membranes. However, the lipids typically used for SLB formation poorly resemble those of bacterial cell membranes due to the lack of available protocols to form SLBs using mixtures of lipids relevant for bacteria such as phosphatidylethanolamine (PE) and phosphatidylglycerol (PG). Although a few reports have been published recently on the formation of SLBs from Escherichia coli lipid extracts, a detailed understanding of these systems is challenging due to the complexity of the lipid composition in such natural extracts. Here, we present for the first time a simple and reliable protocol optimized to form high-quality SLBs using mixtures of PE and PG at compositions relevant for Gram-negative membranes. We show using neutron reflection and quartz microbalance not only that Ca2+ ions and temperature are key parameters for successful bilayer deposition but also that mass transfer to the surface is a limiting factor. Continuous flow of the lipid suspension is thus crucial for obtaining full SLB coverage. We furthermore characterize the resulting bilayers and report structural parameters, for the first time for PE and PG mixtures, which are in good agreement with those reported earlier for pure POPE vesicles. With this protocol in place, more suitable and reproducible studies can be conducted to understand biomolecular processes occurring at cell membranes, for example, for testing specificities and to unravel the mechanism of interaction of antimicrobial peptides.
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| 9. |
- Nielsen, Josefine Eilsø, et al.
(författare)
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Lipid membrane interactions of self-assembling antimicrobial nanofibers : effect of PEGylation
- 2020
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 10, s. 35329-35340
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Tidskriftsartikel (refereegranskat)abstract
- Supramolecular assembly and PEGylation (attachment of a polyethylene glycol polymer chain) of peptides can be an effective strategy to develop antimicrobial peptides with increased stability, antimicrobial efficacy and hemocompatibility. However, how the self-assembly properties and PEGylation affect their lipid membrane interaction is still an unanswered question. In this work, we use state-of-the-art small angle X-ray and neutron scattering (SAXS/SANS) together with neutron reflectometry (NR) to study the membrane interaction of a series of multidomain peptides, with and without PEGylation, known to self-assemble into nanofibers. Our approach allows us to study both how the structure of the peptide and the membrane are affected by the peptide–lipid interactions. When comparing self-assembled peptides with monomeric peptides that are not able to undergo assembly due to shorter chain length, we found that the nanofibers interact more strongly with the membrane. They were found to insert into the core of the membrane as well as to absorb as intact fibres on the surface. Based on the presented results, PEGylation of the multidomain peptides leads to a slight net decrease in the membrane interaction, while the distribution of the peptide at the interface is similar to the non-PEGylated peptides. Based on the structural information, we showed that nanofibers were partially disrupted upon interaction with phospholipid membranes. This is in contrast with the considerable physical stability of the peptide in solution, which is desirable for an extended in vivo circulation time.
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| 10. |
- Nouhi, Shirin, et al.
(författare)
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Sticking particles to solid surfaces using Moringa oleifera proteins as a glue
- 2018
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Ingår i: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 168, s. 68-75
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Tidskriftsartikel (refereegranskat)abstract
- Experimental studies have been made to test the idea that seed proteins from Moringa oleifera which are novel, natural flocculating agents for many particles could be used to promote adhesion at planar interfaces and hence provide routes to useful nanostructures. The proteins bind irreversibly to silica interfaces. Surfaces that had been exposed to protein solutions and rinsed were then exposed to dispersions of sulfonated polystyrene latex. Atomic force microscopy was used to count particle density and identified that the sticking probability was close to 1. Measurements with a quartz crystal microbalance confirmed the adhesion and indicated that repeated exposures to solutions of Moringa seed protein and particles increased the coverage. Neutron reflectivity and scattering experiments indicate that particles bind as a monolayer. The various results show that the 2S albumin seed protein can be used to fix particles at interfaces and suggest routes for future developments in making active filters or improved interfaces for photonic devices.
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