Studies have shown that following exposure to particulate matter, ultrafine fractions (<100 nm) may deposit along the respiratory tract down to the alveolar region. To assess the effects of ...nanoparticles on the lungs, it is essential to address the question of their biophysicochemical interaction with the different pulmonary environments, including the lung lining fluids and the epithelia. Here we examine one of these interactive scenarios and study the role of supported lipid bilayers (SLB) in the effect of 40 nm fluorescent silica particles on living cells. We first study the particle phase behavior in the presence of Curosurf®, a pulmonary surfactant substitute used in replacement therapies. It is found that Curosurf® vesicles interact strongly with the nanoparticles, but do not spontaneously form SLBs. To achieve this goal, we use sonication to reshape the vesicular membranes and induce lipid fusion around the particles. Centrifugal sedimentation and electron microscopy are carried out to determine the optimum coating conditions and layer thickness. We then explore the impact of surfactant SLBs on the cytotoxic potential and interactions towards a malignant epithelial cell line. All in vitro assays indicate that SLBs mitigate the particle toxicity and internalization rates. In the cytoplasm, the particle localization is also strongly coating dependent. It is concluded that SLBs profoundly affect cellular interactions and functions in vitro and could represent an alternative strategy for particle coating. The current data also shed some light on the potential mechanisms pertaining to the particle or pathogen transport through the air-blood barrier.
There is currently a renewed interest for improving household and personal-care formulations to provide more environment-friendly products. Fabric conditioners used as softeners have to fulfill a ...number of stability and biodegradability requirements. They should also display significant adsorption on cotton under the conditions of use. The quantification of surfactant adsorption remains however difficult because the fabric-woven structure is complex and deposited amounts are generally small. Here, we propose a method to evaluate cellulose–surfactant interactions with increased detection sensitivity. The method is based on the use of cellulose nanocrystals (CNCs) in lieu of micron-sized fibers or yarns, combined with different techniques, including light scattering, optical and electron microscopy, and electrophoretic mobility. CNCs are rod-shaped nanoparticles in the form of 200 nm laths that are negatively charged and can be dispersed in bulk solutions. In this work, we use a double-tailed cationic surfactant present in fabric softener. Results show that the surfactants self-assemble into unilamellar, multivesicular, and multilamellar vesicles, and the interaction with CNCs is driven by electrostatics. Mutual interactions are strong and lead to the formation of large-scale aggregates, where the vesicles remain intact at the cellulose surface. The technique developed here could be exploited to rapidly assess the fabric conditioner efficiency obtained by varying the nature and content of their chemical additives.
The atomic numbers and the masses of fragments formed in quasifission reactions are simultaneously measured at scission in ^{48}Ti+^{238}U reactions at a laboratory energy of 286 MeV. The atomic ...numbers are determined from measured characteristic fluorescence x rays, whereas the masses are obtained from the emission angles and times of flight of the two emerging fragments. For the first time, thanks to this full identification of the quasifission fragments on a broad angular range, the important role of the proton shell closure at Z=82 is evidenced by the associated maximum production yield, a maximum predicted by time-dependent Hartree-Fock calculations. This new experimental approach gives now access to precise studies of the time dependence of the N/Z (neutron over proton ratios of the fragments) evolution in quasifission reactions.
We report on the electrostatic complexation between polyelectrolyte-neutral copolymers and oppositely charged 6-nm crystalline nanoparticles. For two different dispersions of oxide nanoparticles, the ...electrostatic complexation gives rise to the formation of stable nanoparticle clusters in the range 20–100 nm. It is found that inside the clusters, the particles are “pasted” together by the polyelectrolyte blocks adsorbed on their surface. Cryo-transmission electronic microscopy allows visualization of the clusters and determination of the probability distribution functions in size and in aggregation number. The comparison between light scattering and cryo-microscopy results suggests the existence of a polymer brush around the clusters.
When polyelectrolyte-neutral block copolymers are mixed in aqueous solutions with oppositely charged species, stable complexes are found to form spontaneously. The mechanism is based on ...electrostatics and on the compensation between the opposite charges. Electrostatic complexes exhibit a core−shell microstructure. In the core, the polyelectrolyte blocks and the oppositely charged species are tightly bound and form a dense coacervate microphase. The shell is made of the neutral chains and surrounds the core. In this paper, we report on the structural and magnetic properties of such complexes made from 6.3 nm diameter superparamagnetic nanoparticles (maghemite γ-Fe2O3) and cationic-neutral copolymers. The copolymers investigated are poly(trimethylammonium ethylacrylate methyl sulfate)-b-poly(acrylamide), with molecular weights 5000-b-30000 g mol-1 and 110000-b-30000 g mol-1. The mixed copolymer−nanoparticle aggregates were characterized by a combination of light scattering and cryo-transmission electron microscopy. Their hydrodynamic diameters were found in the range 70−150 nm, and their aggregation numbers (number of nanoparticles per aggregate) from tens to hundreds. In addition, Magnetic Resonance Spin−Echo measurements show that the complexes have a better contrast in Magnetic Resonance Imaging than single nanoparticles and that these complexes could be used for biomedical applications.
Reducible cationic lipids for gene transfer Wetzer, B; Byk, G; Frederic, M ...
Biochemical journal,
2001-Jun-15, 2001-6-15, 20010615, Letnik:
356, Številka:
Pt 3
Journal Article
Recenzirano
Odprti dostop
One of the main challenges of gene therapy remains the increase of gene delivery into eukaryotic cells. We tested whether intracellular DNA release, an essential step for gene transfer, could be ...facilitated by using reducible cationic DNA-delivery vectors. For this purpose, plasmid DNA was complexed with cationic lipids bearing a disulphide bond. This reduction-sensitive linker is expected to be reduced and cleaved in the reducing milieu of the cytoplasm, thus potentially improving DNA release and consequently transfection. The DNA--disulphide-lipid complexation was monitored by ethidium bromide exclusion, and the size of complexes was determined by dynamic light scattering. It was found that the reduction kinetics of disulphide groups in DNA--lipid complexes depended on the position of the disulphide linker within the lipid molecule. Furthermore, the internal structure of DNA--lipid particles was examined by small-angle X-ray scattering before and after lipid reduction. DNA release from lipid complexes was observed after the reduction of disulphide bonds of several lipids. Cell-transfection experiments suggested that complexes formed with selected reducible lipids resulted in up to 1000-fold higher reporter-gene activity, when compared with their analogues without disulphide bonds. In conclusion, reduction-sensitive groups introduced into cationic lipid backbones potentially allow enhanced DNA release from DNA--lipid complexes after intracellular reduction and represent a tool for improved vectorization.
We investigate whether block copolymers of controlled effective segregation strength can be designed via a novel controlled radical polymerization technique that allows statistical polymerization of ...different monomers in either one of the constituting blocks: We examine the morphologies and segregation regimes of two families of poly(styrene-stat-(acrylic acid))-b-poly(acrylic acid) diblocks of different block ratios (i.e., one asymmetric and one symmetric), comprising a statistical first block of variable ratio of styrene vs acrylic acid and a second PAA block. Thanks to small-angle X-ray scattering and transmission electron microscopy, we observe that as the composition of the statistical first block is varied, such asymmetric and symmetric diblocks form strongly to weakly microphase-separated structures, respectively, presenting spherical and well-ordered lamellar symmetries, or homogeneous (disordered) phases. We thus demonstrate that the segregation strength can be quantitatively controlled by the composition of the statistical first block, regardless of the diblock symmetry.
Noticeable modifications of in-serum transfection efficiency of dioctadecylamidoglycyl-spermine (DOGS)–DNA complexes are observed, depending on DNA condensation conditions. The structures of the ...complexes are studied, keeping in mind the variability of lipid polymorphism, by cryo-transmission electron microscopy and X-ray diffraction. By increasing both pH and ionic strength, well-organised lamellar structures with a period of 65 Å replace supramicellar aggregates. A relationship between the structures and their in-vitro transfection activity is established. Efficiency in the presence of serum is maintained when a lamellar arrangement is involved.
Studies have shown that following exposure to particulate matter, ultrafine fractions (<100 nm) may deposit along the respiratory tract down to the alveolar region. To assess the effects of ...nanoparticles on the lungs, it is essential to address the question of their biophysicochemical interaction with the different pulmonary environments, including the lung lining fluids and the epithelia. Here we examine one of these interactive scenarios and study the role of supported lipid bilayers (SLB) in the effect of 40 nm fluorescent silica particles on living cells. We first study the particle phase behavior in the presence of Curosurf®, a pulmonary surfactant substitute used in replacement therapies. It is found that Curosurf® vesicles interact strongly with the nanoparticles, but do not spontaneously form SLBs. To achieve this goal, we use sonication to reshape the vesicular membranes and induce lipid fusion around the particles. Centrifugal sedimentation and electron microscopy are carried out to determine the optimum coating conditions and layer thickness. We then explore the impact of surfactant SLBs on the cytotoxic potential and interactions towards a malignant epithelial cell line. All
in vitro
assays indicate that SLBs mitigate the particle toxicity and internalization rates. In the cytoplasm, the particle localization is also strongly coating dependent. It is concluded that SLBs profoundly affect cellular interactions and functions
in vitro
and could represent an alternative strategy for particle coating. The current data also shed some light on the potential mechanisms pertaining to the particle or pathogen transport through the air-blood barrier.
Supported lipid bilayers on 40 nm silica nanoparticles from an exogenous pulmonary surfactant.
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