5 research outputs found
Effect of Functionalized Gold Nanoparticles on Floating Lipid Bilayers
The
development of novel nano-engineered materials poses important
questions regarding the impact of these new materials on living systems.
Possible adverse effects must be assessed in order to prevent risks
for health and the environment. On the other hand, a thorough understanding
of their interaction with biological systems might also result in
the creation of novel biomedical applications. We present a study
on the interaction of model lipid membranes with gold nanoparticles
(AuNP) of different surface modifications. Neutron reflectometry experiments
on zwitterionic lipid double bilayers were performed in the presence
of AuNP functionalized with cationic and anionic head groups. Structural
information was obtained that provided insight into the fate of the
AuNPs with regard to the integrity of the model cell membranes. The
AuNPs functionalized with cationic head groups penetrate into the
hydrophobic moiety of the lipid bilayers and cause membrane disruption
at an increased concentration. In contrast, the AuNPs functionalized
with anionic head groups do not enter but seem to impede the destruction
of the lipid bilayer at an alkaline pH. The information obtained might
influence the strategy for a better nanoparticle risk assessment based
on a surface charge evaluation and contribute to nano-safety considerations
during their design
Small-Angle Neutron Scattering Reveals the Nanostructure of Liposomes with Embedded OprF Porins of Pseudomonas aeruginosa
The
use of liposomes
as drug delivery systems emerged in the last decades in view of their
capacity and versatility to deliver a variety of therapeutic agents.
By means of small-angle neutron scattering (SANS), we performed a
detailed characterization of liposomes containing outer membrane protein
F (OprF), the main porin of the Pseudomonas aeruginosa bacterium outer membrane. These OprF-liposomes are the basis of
a novel vaccine against this antibiotic-resistant bacterium, which
is one of the main hospital-acquired pathogens and causes each year
a significant number of deaths. SANS data were analyzed by a specific
model we created to quantify the crucial information about the structure
of the liposome containing OprF, including the lipid bilayer structure,
the amount of protein in the lipid bilayer, the average protein localization,
and the effect of the protein incorporation on the lipid bilayer.
Quantification of such structural information is important to enhance
the design of liposomal delivery systems for therapeutic applications
Submicrometer 3D Structural Evidence of Fuel Cell Membrane Heterogeneous Degradation
Polymer
membranes used in the proton exchange membrane fuel cell
(PEMFC) technology are subject to severe chemical and physical degradations
during operation. A microscopic diagnosis of the effects of aging
on the microstructure of benchmark perfluorinated sulfonic acid (PFSA)
membranes is crucial to developing long-lasting devices. We report
here the first μSAXS study of membranes aged for 2500 h in a
stack. SAXS spectra recorded with submicrometer resolution in-plane
and along the membrane thickness provide a 3D mapping of the aging
effect. Nanoscale heterogeneities are evidenced and found to depend
on the membrane position relative to the electrodes, to the air inlets,
and proximity to channels (distributing gas) or ribs (collecting the
current). Long-term aging in a fuel cell operating in stationary conditions
around 65 °C results in a small voltage degradation rate of 13
μV/h, without any evidence of membrane failure, but to an irreversible
over-swelling of the membrane due to polymer relaxation. Regions under
the gas distribution channels close to the air inlet are profoundly
degraded due to an increased water gradient concentration from the
cathode to the anode. These observations provide a novel and unique
insight for developing new strategies toward the design of more durable
polymers inserted in smart fuel cells
Functional Characterization of Cell-Free Expressed OprF Porin from <i>Pseudomonas aeruginosa</i> Stably Incorporated in Tethered Lipid Bilayers
OprF
has a central role in <i>Pseudomonas aeruginosa</i> virulence
and thus provides a putative target for either vaccines
or antibiotic cofactors that could overcome the bacterium’s
natural resistance to antibiotics. Here we describe a procedure to
optimize the production of highly pure and functional OprF porins
that are then incorporated into a tethered lipid bilayer. This is
a stable biomimetic system that provides the capability to investigate
structural aspects and function of OprF using and neutron reflectometry
and electrical impedance spectroscopy. The recombinant OprF produced
using the optimized cell-free procedure yielded a quantity of between
0.5 to 1.0 mg/mL with a purity ranging from 85 to 91% in the proteoliposomes.
The recombinant OprF is capable of binding IFN-γ and is correctly
folded in the proteoliposomes. Because OprF proteins form pores the
biomimetic system allowed the measurement of OprF conductance using
impedance spectroscopy. The neutron reflectometry measurements showed
that the OprF protein is incorporated into the lipid bilayer but with
parts of the protein in both the regions above and below the lipid
bilayer. Those structural aspects are coherent with the current assumed
structure of a transmembrane N-terminal domain composed by eight stranded
beta-barrels and a globular C-terminal domain located in the periplasm.
Currently there are no crystal structures available for OprF. The
experimental model system that we describe provides a basis for further
fundamental studies of OprF and particularly for the ongoing biotechnological
development of OprF as a target for antibacterial drugs
Damping Off Terahertz Sound Modes of a Liquid upon Immersion of Nanoparticles
The control of phonon
propagation in nanoparticle arrays is one
of the frontiers of nanotechnology, potentially enabling the discovery
of materials with unknown functionalities for potential innovative
applications. The exploration of the terahertz window appears quite
promising as phonons in this range are the leading carriers of heat
transport in insulators and their control is the key to implement
devices for heat flow management. Unfortunately, this scientific field
is still in its infancy, and even a basic topic such as the influence
of floating nanoparticles on the terahertz phonon propagation of a
colloidal suspension still eludes a firm answer. Shedding some light
on this topic is the main motivation of the present work, which focuses
an inelastic X-ray scattering (IXS) measurements on a dilute suspension
of Au nanospheres in water. Measured spectra showed a nontrivial shape
displaying multiple inelastic features that, based on a Bayesian inference
analysis, we assign to phonon modes propagating throughout the nanoparticle
interior. Surprisingly, the spectra bear no evidence of propagating
modes, which are known to dominate the spectrum of pure water, owing
to the scattering that these modes suffer from the sparse nanoparticles
in suspension. In perspective, this finding may inspire simple routes
to manipulate high-frequency acoustic propagation in hybridliquid
and solidmaterials