Wire-Active Microrheology to Differentiate Viscoelastic Liquids from Soft Solids.

Viscoelastic liquids are characterized by a finite static viscosity and a yield stress of zero, whereas soft solids have an infinite viscosity and a non-zero yield stress. The rheological nature of viscoelastic materials has long been a challenge and is still a matter of debate. Here, we provide for the first time the constitutive equations of linear viscoelasticity for magnetic wires in yield-stress materials, together with experimental measurements by using magnetic rotational spectroscopy (MRS). In MRS, the wires were subjected to a rotational magnetic field as a function of frequency and the motion of the wire was monitored by using time-lapse microscopy. The studied soft solids were aqueous dispersions of gel-forming polysaccharide (gellan gum) at concentrations above the gelification point. It was found that soft solids exhibited a clear and distinctive signature compared with viscous and viscoelastic liquids. In particular, the average wire rotation velocity equaled zero over a broad frequency range. We also showed that the MRS technique is quantitative. The equilibrium elastic modulus was retrieved from the wire oscillation amplitudes, and agrees with polymer-dynamics theory.

Effects of brake wear nanoparticles on the protection and repair functions of the airway epithelium.

Long term exposure to particulate air pollution is known to increase respiratory morbidity and mortality. In urban areas with dense traffic most of these particles are generated by vehicles, via engine exhaust or wear processes. Non-exhaust particles come from wear processes such as those concerning brakes and their toxicity is little studied. To improve our understanding of the lung toxicity mechanisms of the nanometric fraction of brake wear nanoparticles (BWNPs), we studied whether these particles affect the barrier properties of the respiratory epithelium considering particle translocation, mucus production and repair efficiency. The Calu-3 cell line grown in two-compartment chambers was used to mimic the bronchial epithelial barrier. BWNPs detected by single-particle ICP-MS were shown to cross the epithelial tissue in small amounts without affecting the barrier integrity properties, because the permeability to Lucifer yellow was not increased and there was no cytotoxicity as assessed by the release of lactate-dehydrogenase. The interaction of BWNPs with the barrier did not induce a pro-inflammatory response, but increased the expression and production of MU5AC, a mucin, by a mechanism involving the epidermal growth factor receptor pathway. During a wound healing assay, BWNP-loaded cells exhibited the same ability to migrate, but those at the edge of the wound showed higher 5-ethynyl-2'-deoxyuridine incorporation, suggesting a higher proliferation rate. Altogether these results showed that BW. NPs do not exert overt cytotoxicity and inflammation but can translocate through the epithelial barrier in small amounts and increase mucus production, a key feature of acute inflammatory and chronic obstructive pulmonary diseases. Their loading in epithelial cells may impair the repair process through increased proliferation.

Probing DNA-Amyloid Interaction and Gel Formation by Active Magnetic Wire Microrheology.

Recent studies have shown that bacterial nucleoid-associated proteins (NAPs) can bind to DNA and result in altered structural organization and bridging interactions. Under spontaneous self-assembly, NAPs may also form anisotropic amyloid fibers, whose effects are still more significant on DNA dynamics. To test this hypothesis, microrheology experiments on dispersions of DNA associated with the amyloid terminal domain (CTR) of the bacterial protein Hfq were performed using magnetic rotational spectroscopy (MRS). In this chapter, we survey this microrheology technique based on the remote actuation of magnetic wires embedded in a sample. MRS is interesting as it is easy to implement and does not require complex procedures regarding data treatment. Pertaining to the interaction between DNA and amyloid fibers, it is found that DNA and Hfq-CTR protein dispersions behave like a gel, an outcome that suggests the formation of a network of amyloid fibers cross-linked with the DNA strands. In contrast, the pristine DNA and Hfq-CTR dispersions behave as purely viscous liquids. To broaden the scope of the MRS technique, we include theoretical predictions for the rotation of magnetic wires regarding the generic behaviors of basic rheological models from continuum mechanics, and we list the complex fluids studied by this technique over the past 10 years.

Advanced Eco-Friendly Formulations of Guar Biopolymer-Based Textile Conditioners.

Fabric conditioners are household products used to impart softness and fragrance to textiles. They are colloidal dispersions of cationic double chain surfactants that self-assemble in vesicles. These surfactants are primarily derived from palm oil chemical modification. Reducing the content of these surfactants allows to obtain products with lower environmental impact. Such a reduction, without adverse effects on the characteristics of the softener and its performance, can be achieved by adding hydrophilic biopolymers. Here, we review the role of guar biopolymers modified with cationic or hydroxyl-propyl groups, on the physicochemical properties of the formulation. Electronic and optical microscopy, dynamic light scattering, X-ray scattering and rheology of vesicles dispersion in the absence and presence of guar biopolymers are analyzed. Finally, the deposition of the new formulation on cotton fabrics is examined through scanning electron microscopy and a new protocol based on fluorescent microscopy. With this methodology, it is possible to quantify the deposition of surfactants on cotton fibers. The results show that the approach followed here can facilitate the design of sustainable home-care products.

Association of nutrient intake and wheeze or asthma in a Greek pre-school population.

The rise of asthma prevalence in children observed the last years might be related to several dietary factors/components as suggested by several researchers. We aimed to evaluate the potential relationship between certain nutrients intake and asthma occurrence in a population of pre-school children. In the framework of the cross-sectional study 'Growth, Exercise and Nutrition Epidemiological Study In pre-schoolers', data were collected from 1964 children, aged 24-72 months, living in five different counties in Greece. The International Study of Asthma and Allergies in Childhood questionnaire was used to assess asthma related outcomes. Dietary intake was assessed with 3 days diet records. The prevalence of ever wheeze, current wheeze and diagnosed asthma was 37.7%, 27.5% and 10.5% respectively. Dietary intake of magnesium had a 0.5% and 0.6% increase in the reported risk of current wheeze and diagnosed asthma respectively. On the contrary a decrease in the prevalence of ever (OR: 0.997, 95% CI: 0.995-1.000) and current wheeze (OR: 0.996, 95% CI: 0.993-0.999) was associated with vitamin C intake. Calcium intake slightly decreased the risk of current wheeze (OR: 0.999, 95% CI: 0.998-0.999). An increase of 2% of the risk of reporting ever or current wheeze was associated with mono-unsaturated fatty acid intake. Magnesium intake was the only independent predictor for doctor's diagnosed asthma. We conclude that dietary intake of vitamin C and calcium seem to have a protective effect on the incidence of wheeze in pre-school children, whereas magnesium and mono-unsaturated fatty acid may have a harmful role.

Revealing the pulmonary surfactant corona on silica nanoparticles by cryo-transmission electron microscopy.

When inhaled, nanoparticles (NPs) deposit in alveoli and transit through the pulmonary surfactant (PS), a biofluid made of proteins and phospholipid vesicles. They form a corona reflecting the PS-nanomaterial interaction. Since the corona determines directly the NPs' biological fate, the question of its nature and structure is central. Here, we report on the corona architecture formed after incubation of positive or negative silica particles with Curosurf®, a biomimetic pulmonary surfactant of porcine origin. Using optical, electron and cryo-electron microscopy (cryo-TEM), we determine the pulmonary surfactant corona structure at different scales of observation. Contrary to common belief, the PS corona is not only constituted by phospholipid bilayers surrounding NPs but also by multiple hybrid structures derived from NP-vesicle interaction. Statistical analysis of cryo-TEM images provides interesting highlights about the nature of the corona depending on the particle charge. The influence of Curosurf® pre- or post-treatment is also investigated and demonstrates the need for protocol standardization.

Effect of Nanoparticles on the Bulk Shear Viscosity of a Lung Surfactant Fluid.

Inhaled nanoparticles (<100 nm) reaching the deep lung region first interact with the pulmonary surfactant, a thin lipid film lining the alveolar epithelium. To date, most biophysical studies have focused on particle-induced modifications of the film interfacial properties. In comparison, there is less work on the surfactant bulk properties and on their changes upon particle exposure. Here we study the viscoelastic properties of a biomimetic pulmonary surfactant in the presence of various engineered nanoparticles. The microrheology technique used is based on the remote actuation of micron-sized wires via the application of a rotating magnetic field and on time-lapse optical microscopy. It is found that particles strongly interacting with lipid vesicles, such as cationic silica (SiO2, 42 nm) and alumina (Al2O3, 40 nm) induce profound modifications of the surfactant flow properties, even at low concentrations. In particular, we find that silica causes fluidification, while alumina induces a liquid-to-soft solid transition. Both phenomena are described quantitatively and accounted for in the context of colloidal physics models. It is finally suggested that the structure and viscosity changes could impair the fluid reorganization and recirculation occurring during breathing.

Design and Applications of a Fluorescent Labeling Technique for Lipid and Surfactant Preformed Vesicles.

Amphiphilic molecules such as surfactants, lipids, and block copolymers can be assembled into bilayers and form vesicles. Fluorescent membrane labeling methods require the use of dye molecules that can be inserted into the bilayers at different stages of synthesis. To our knowledge, there is no generalized method for labeling preformed vesicles. Herein, we develop a versatile protocol that is suitable to both surfactant and lipid preformed vesicles and requires no separation or purification steps. On the basis of the lipophilic carbocyanine green dye PKH67, the methodology is assessed on zwitterionic phosphatidylcholine vesicles. To demonstrate its versatility, it is applied to dispersions of anionic or cationic vesicles, such as a drug administrated to premature infants with respiratory distress syndrome, or a vesicle formulation used as a fabric softener for home care applications. By means of fluorescence microscopy, we then visualize the interaction mechanisms of nanoparticles crossing live cell membranes and of surfactants adsorbed on a cotton fabric. These results highlight the advantages of a membrane labeling technique that is simple and applicable to a large number of soft matter systems.

Preparation of Porous Polymeric Membranes Based on a Pyridine Containing Aromatic Polyether Sulfone.

Polymeric membranes, based on a polysulfone-type aromatic polyether matrix, were successfully developed via the non-solvent induced phase separation (NIPS) method. The polyethersulfone type polymer poly[2-(4-(diphenylsulfonyl)-phenoxy)-6-(4-phenoxy) pyridine] (PDSPP) was used as the membrane matrix, and mixed with its sulfonated derivative (SPDSPP) and a polymeric porogen. The SPDPPP was added to impart hydrophilicity, while at the same time maintaining the interactions with the non-sulfonated aromatic polyether forming the membrane matrix. Different techniques were used for the membranes' properties characterization. The results revealed that the use of the non-sulfonated and sulfonated polymers of the same polymeric backbone, at certain compositions, can lead to membranes with controllable porosity and hydrophilicity.

Diet quality of preschoolers in Greece based on the Healthy Eating Index: the GENESIS study.

BACKGROUND: The current study aimed to assess the diet quality of Greek preschoolers and the potential role of several sociodemographic factors related to it. METHODS: A representative sample of 2,287 Greek children aged 2 to 5 years (from the Growth, Exercise, and Nutrition Epidemiological Study In preSchoolers) was used in this work. Dietary intake data was obtained using a combination of techniques comprising weighed food records, 24-hour recalls, and food diaries. A Healthy Eating Index (HEI) score was calculated summing the individual scores (0 to 10) assigned to each one of 10 index components. RESULTS: Eighty percent of participants had an HEI score <50 (ie, "poor" diet), 0.4% had an HEI score >80 (ie, "good" diet), and the overall mean HEI score was 59. HEI scores were significantly higher among boys, children aged 4 to 5 years, children participating in moderate to vigorous physical activities for more than 3 hours per week, children living in rural or small towns, and those whose mothers were employed and had higher educational status (>12 years). HEI score was also found to be strongly associated with several macronutrient and micronutrient intakes. CONCLUSIONS: Based on HEI scores, the vast majority of Greek preschoolers was found to have a poor diet. Moreover, low HEI scores were associated with low levels of physical activity, low vegetable intake, high saturated fat intake, lower maternal educational level, and unemployment status.