| 1. |
- Armanious, Antonius, 1981, et al.
(author)
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Probing the Separation Distance between Biological Nanoparticles and Cell Membrane Mimics Using Neutron Reflectometry with Sub-Nanometer Accuracy
- 2022
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In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 144:45, s. 20726-20738
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Journal article (peer-reviewed)abstract
- Nanoparticle interactions with cellular membranes are controlled by molecular recognition reactions and regulate a multitude of biological processes, including virus infections, biological nanoparticle-mediated cellular communication, and drug delivery applications. Aided by the design of various supported cell membrane mimics, multiple methods have been employed to investigate these types of interactions, revealing information on nanoparticle coverage, interaction kinetics, as well as binding strength; however, precise quantification of the separation distance across which these delicate interactions occur remains elusive. Here, we demonstrate that carefully designed neutron reflectometry (NR) experiments followed by an attentive selection and application of suitable theoretical models offer a means to quantify the distance separating biological nanoparticles from a supported lipid bilayer (SLB) with sub-nanometer precision. The distance between the nanoparticles and SLBs was tuned by exploiting either direct adsorption or specific binding using DNA tethers with different conformations, revealing separation distances of around 1, 3, and 7 nm with nanometric accuracy. We also show that NR provides precise information on nanoparticle coverage, size distribution, material composition, and potential structural changes in the underlying planar SLB induced upon nanoparticle binding. The precision with which these parameters could be quantified should pave an attractive path for investigations of the interactions between nanoparticles and interfaces at length scales and resolutions that were previously inaccessible. This thus makes it possible to, for example, gain an in-depth understanding of the molecular recognition reactions of inorganic and biological nanoparticles with cellular membranes.
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| 2. |
- Caselli, Lucrezia, et al.
(author)
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Boosting Membrane Interactions and Antimicrobial Effects of Photocatalytic Titanium Dioxide Nanoparticles by Peptide Coating
- 2024
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In: Small. - : John Wiley and Sons Inc. - 1613-6810 .- 1613-6829.
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Journal article (peer-reviewed)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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| 3. |
- Neville, George M., et al.
(author)
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Interactions of Choline and Geranate (CAGE) and Choline Octanoate (CAOT) Deep Eutectic Solvents with Lipid Bilayers
- 2023
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In: Advanced Functional Materials. - 1616-301X.
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Journal article (peer-reviewed)abstract
- Mixtures between choline and geranic acid (CAGE) have previously been shown to insert into lipid bilayers. This may be useful for the transdermal delivery of larger pharmaceuticals, however, little is known about the mechanism of activity. By comparing the interactions between CAGE and lipid bilayers with those of a less-active, yet closely-related analogue, choline octanoic acid (CAOT), a chemical basis can be investigated. Overall, six systems are studied here by neutron reflectivity, where d54-1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) solid-supported phospholipid bilayers are first formed on SiO2 substrates before exposure to the deep eutectic solvent (DES). Components of the DES could be identified within the bilayer by exploiting contrast variation and selective deuteration. CAGE is shown to be a mild disruptive agent, free to insert and diffuse across the bilayer, preserving much of the bilayer integrity. Experiments identify co-mingling of geranate ions inhibits the efficient packing of lipid tails, increasing hydration across the bilayer. Conversely, CAOT is found to both exchange and remove lipid molecules to achieve incorporation, inducing swelling and the formation of solvent patches. It appears these behaviors derive from the structures of the anions and thus amphiphilicity of the DES, laying the foundations for the rational design and optimization of these candidates toward transdermal delivery.
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| 4. |
- Pace, Hudson, 1982, et al.
(author)
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Structure and Composition of Native Membrane Derived Polymer-Supported Lipid Bilayers
- 2018
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In: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 90:21, s. 13065-13072
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Journal article (peer-reviewed)abstract
- Over the last two decades, supported lipid bilayers (SLBs) have been extensively used as model systems to study cell membrane structure and function. While SLBs have been traditionally produced from simple lipid mixtures, there has been a recent surge in compositional complexity to better mimic cellular membranes and thereby bridge the gap between classic biophysical approaches and cell experiments. To this end, native cellular membrane derived SLBs (nSLBs) have emerged as a new category of SLBs. As a new type of biomimetic material, an analytical workflow must be designed to characterize its molecular composition and structure. Herein, we demonstrate how a combination of fluorescence microscopy, neutron reflectometry, and secondary ion mass spectrometry offers new insights on structure, composition, and quality of nSLB systems formed using so-called hybrid vesicles, which are a mixture of native membrane material and synthetic lipids. With this approach, we demonstrate that the nSLB formed a continuous structure with complete mixing of the synthetic and native membrane components and a molecular stoichiometry that essentially mirrors that of the hybrid vesicles. Furthermore, structural investigation of the nSLB revealed that PEGylated lipids do not significantly thicken the hydration layer between the bilayer and substrate when on silicon substrates; however, nSLBs do have more topology than their simpler, purely synthetic counterparts. Beyond new insights regarding the structure and composition of nSLB systems, this work also serves to guide future researchers in producing and characterizing nSLBs from their cellular membrane of choice.
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| 5. |
- Paracini, Nicoló, et al.
(author)
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Lipopolysaccharides at Solid and Liquid Interfaces : Models for Biophysical Studies of the Gram-negative Bacterial Outer Membrane
- 2022
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In: Advances in Colloid and Interface Science. - : Elsevier. - 0001-8686 .- 1873-3727. ; 301
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Journal article (peer-reviewed)abstract
- Lipopolysaccharides (LPSs) are a constitutive element of the cell envelope of Gram-negative bacteria, representing the main lipid in the external leaflet of their outer membrane (OM) lipid bilayer. These unique surface-exposed glycolipids play a central role in the interactions of Gram-negative organisms with their surrounding environment and represent a key element for protection against antimicrobials and the development of antibiotic resistance. The biophysical investigation of a wide range of different types of in vitro model membranes containing reconstituted LPS has revealed functional and structural properties of these peculiar membrane lipids, providing molecular-level details of their interaction with antimicrobial compounds. LPS assemblies reconstituted at interfaces represent a versatile tool to study the properties of the Gram-negative OM by exploiting several surface-sensitive techniques, in particular X-ray and neutron scattering, which can probe the structure of thin films with sub-nanometer resolution. This review provides an overview of different approaches employed to investigate structural and biophysical properties of LPS, focusing on studies on Langmuir monolayers of LPS at the air/liquid interface and a range of supported LPS-containing model membranes reconstituted at solid/liquid interfaces.
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| 6. |
- Parra-Ortiz, Elisa, et al.
(author)
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Effects of oxidation on the physicochemical properties of polyunsaturated lipid membranes
- 2019
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In: Journal of Colloid and Interface Science. - : ACADEMIC PRESS INC ELSEVIER SCIENCE. - 0021-9797 .- 1095-7103. ; 538, s. 404-419
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Journal article (peer-reviewed)abstract
- The exposure of biological membranes to reactive oxygen species (ROS) plays an important role in many pathological conditions such as inflammation, infection, or sepsis. ROS also modulate signaling processes and produce markers for damaged tissue. Lipid peroxidation, mainly affecting polyunsaturated phospholipids, results in a complex mixture of oxidized products, which may dramatically alter membrane properties. Here, we have employed a set of biophysical and surface-chemical techniques, including neutron and X-ray scattering, to study the structural, compositional, and stability changes due to oxidative stress on phospholipid bilayers composed of lipids with different degrees of polyunsaturation. In doing so, we obtained real-time information about bilayer degradation under in situ UV exposure using neutron reflectometry. We present a set of interrelated physicochemical effects, including gradual increases in area per molecule, head group and acyl chain hydration, as well as bilayer thinning, lateral phase separation, and defect formation leading to content loss upon membrane oxidation. Such effects were observed to depend on the presence of polyunsaturated phospholipids in the lipid membrane, suggesting that these may also play a role in the complex oxidation processes occurring in cells.
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