| 1. |
- Malekkhaiat Häffner, Sara, et al.
(författare)
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Nanoclay-induced bacterial flocculation for infection confinement
- 2020
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 562, s. 71-80
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Tidskriftsartikel (refereegranskat)abstract
- Effects of size and charge of anionic nanoclays on their interactions with bacteria-mimicking lipid membranes, bacterial lipopolysaccharide (LPS), and Gram-negative bacteria were investigated using ellipsometry, dynamic light scattering, ζ-potential measurements, and confocal microscopy combined with Live/Dead staining. Based on particle size and charge density, three different anionic hectorite nanoclays were employed, and investigated in the presence and absence of the net cationic human antimicrobial peptide LL-37 (LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES). In the absence of this peptide, the nanoclays were found not to bind to similarly anionic bacteria-mimicking model phospholipid membranes, nor to destabilize these. Similarly, while all nanoclays induced aggregation of Escherichia coli bacteria, the flocculated bacteria remained alive after aggregation. In contrast, LL-37 alone, i.e. in the absence of nanoclay particles, displays antimicrobial properties through membrane lysis, but does not cause bacterial aggregation in the concentration range investigated. After loading the nanoclays with LL-37, potent bacterial aggregation combined with bacterial membrane lysis was observed for all nanoclay sizes and charge densities. Demonstrating the potential of these combined systems for confinement of infection, LPS-induced NF-κB activation in human monocytes was found to be strongly suppressed after nanoclay-mediated aggregation, with a wide tolerance for nanoparticle size and charge density.
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| 2. |
- Nordström, Randi, et al.
(författare)
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Membrane Interactions of Antimicrobial Peptide-Loaded Microgels
- 2020
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 562, s. 322-332
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, lipid membrane interactions of anionic poly(ethyl acrylate-co-methacrylic acid) (MAA) microgels as carriers for the cationic antimicrobial peptide LL-37 (LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES) were investigated. In doing so, neutron reflectometry (NR), Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR-ATR), zeta potential, ellipsometry, and circular dichroism spectroscopy (CD) experiments were employed to investigate the relative importance of membrane interactions of peptide-loaded microgel particles and of released peptide. For the free peptide, NR results showed membrane binding occurring preferentially in the tail region in a concentration-dependent manner. At low peptide concentration (0.3 mu M) only peptide insertion in the outer leaflet was seen, however, pronounced membrane defects and peptide present in both leaflets was observed at higher peptide concentration (5.0 LL-37 loaded into MAA microgels qualitatively mirrored these effects regarding both peptide localization within the membrane and concentration dependent defect formation. In addition, very limited membrane binding of microgel particles was observed, in agreement with FTIR-ATR and liposome leakage results. FTIR-ATR showed LL-37 to undergo alpha-helix formation on membrane insertion, also supported by CD results, the kinetics of which was substantially reduced for microgel-loaded LL-37 due to sustained peptide release. Together, these findings demonstrate that membrane interactions for microgel-loaded LL-37 are dominated by released peptide, but also that slow release of microgel-loaded LL-37 translates into kinetic effects on peptide-membrane interactions, relating to both peptide localization within the bilayer, and to bilayer structure.
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| 3. |
- Parra-Ortiz, Elisa, et al.
(författare)
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Oxidation of Polyunsaturated Lipid Membranes by Photocatalytic Titanium Dioxide Nanoparticles : Role of pH and Salinity
- 2020
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 12:29, s. 32446-32460
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, UV-induced membrane destabilization by TiO2 (anatase) nanoparticles was investigated by neutron reflectometry (NR), small-angle X-ray scattering (SAXS), quartz crystal microbalance with dissipation (QCM-D), dynamic light scattering (DLS), and ζ-potential measurements for phospholipid bilayers formed by zwitterionic palmitoyloleoylphosphatidylcholine (POPC) containing biologically relevant polyunsaturations. TiO2 nanoparticles displayed pH-dependent binding to such bilayers. Nanoparticle binding alone, however, has virtually no destabilizing effects on the lipid bilayers. In contrast, UV illumination in the presence of TiO2 nanoparticles activates membrane destabilization as a result of lipid oxidation caused by the generation of reactive oxygen species (ROS), primarily •OH radicals. Despite the short diffusion length characterizing these, the direct bilayer attachment of TiO2 nanoparticles was demonstrated to not be a sufficient criterion for an efficient UV-induced oxidation of bilayer lipids, the latter also depending on ROS generation in bulk solution. From SAXS and NR, minor structural changes were seen when TiO2 was added in the absence of UV exposure, or on UV exposure in the absence of TiO2 nanoparticles. In contrast, UV exposure in the presence of TiO2 nanoparticles caused large-scale structural transformations, especially at high ionic strength, including gradual bilayer thinning, lateral phase separation, increases in hydration, lipid removal, and potential solubilization into aggregates. Taken together, the results demonstrate that nanoparticle-membrane interactions ROS generation at different solution conditions act in concert to induce lipid membrane destabilization on UV exposure and that both of these need to be considered for understanding the performance of UV-triggered TiO2 nanoparticles in nanomedicine.
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