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.
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 gamma-Fe(2)O(3)) 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.
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.
This work deals with the determination of polymer effective charge based on the sensitivity of detection in capillary electrophoresis using indirect UV detection. In this detection mode, the ...polyelectrolyte (solute) displaces a certain quantity of probe contained in the background electrolyte and having the same charge as the solute. This quantity of displaced probe is directly correlated to the effective charge of the solute. Contrary to other electrophoretic methods generally used for monitoring changes in effective charge, this methodology is not based on the effective mobility of the polyelectrolyte (i.e., migration times) but on the sensitivity of detection (i.e., peak areas). Experimental values of effective charge obtained for statistical copolymers of poly(acrylamide-co-sodium 2-acrylamido-2-methylpropanesulfonate), for homopolymers of poly(diallyldimethylammonium chloride), poly(acrylic acid), and poly(metacrylic acid), are compared to the Manning theory of charge condensation. Interestingly, this methodology can be used for the characterization of macromolecular architecture since the effective charge of copolymers highly depends on the repartition of the charged monomers along the polymer chain. As an example, this methodology can easily distinguish statistical copolymers from diblock copolymers of similar chemical charge densities. Experiments were carried out on diblock copolymers of poly(acrylic acid)-b-poly(ethylene oxide) (PAA-b-PEO) and poly(methacrylic acid)-b-poly(ethylene oxide) (PMAA-b-PEO). The variation of the sensitivity of detection of statistically charged copolymers in the indirect UV mode with the chemical charge density is also discussed in detail.
PDF
