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In recent years, there has been a renewed interest in complex coacervation, driven by concerted efforts to offer novel experimental and theoretical insights into electrostatic charge-induced association. While previous studies have primarily focused on polyelectrolytes, proteins or surfactants, our work explores the potential of using cerium (CeO2) and iron ({\gamma}-Fe2O3) oxide nanoparticles (NPs) to develop innovative nanomaterials. By combining various charged species, such as polyelectrolytes, charged neutral block copolymers and coated NPs, we study a wide variety of complexation patterns and compare them using isothermal titration calorimetry, light scattering and microscopy. These techniques confirm that the titration of oppositely charged species occurs in two steps: the formation of polyelectrolyte complexes and subsequent phase (or microphase) separation, depending on the system studied. Across all examined cases, the entropic contribution to the total free energy surpasses the enthalpic contribution, in agreement with counterion release mechanisms. Furthermore, our investigation reveals a consistent asymmetry in the reaction enthalpy associated with the secondary process, with exothermic profiles observed upon the addition of cationic species to anionic ones and endothermic profiles in the reverse case.

Cellular microrheology has shown that cancer cells with high metastatic potential are softer compared to non-tumorigenic normal cells. These findings rely on measuring the apparent Young modulus of whole cells using primarily atomic force microscopy. This study aims to explore whether alternative mechanical parameters have discriminating features with regard to metastatic potential. Magnetic rotational spectroscopy (MRS) is employed in the examination of mammary epithelial cell lines: MCF-7 and MDA-MB-231, representing low and high meta-static potential, alongside normal-like MCF-10A cells. MRS utilizes active micron-sized magnetic wires in a rotating magnetic field to measure the viscosity and elastic modulus of the cy-toplasm. All three cell lines display viscoelastic behavior, with cytoplasmic viscosities ranging from 10-70 Pa s and elastic moduli from 30-80 Pa. It is found that the tumorigenic MCF-7 and MDA-MB-231 cells are softer than the MCF-10A cells, with a twofold decrease in elastic modulus. To differentiate cells with low and high malignancy however, viscosity emerges as the more discriminating parameter, as MCF-7 exhibits a 5 times higher viscosity as compared to MDA-MB-231. These findings highlight the sensitivity of cytoplasmic viscosity to metastatic potential, suggesting its potential utility as a mechanical marker for malignant cancer cells.

Fabric softeners are formulated to enhance textile softness and impart a pleasant scent. One of the most efficient technologies for controlled fragrance delivery onto fabrics involves encapsulating scent molecules in polymer capsules. Here, we investigate the adsorption of anionic fragrance cap-sules on cotton fabrics with the goal of reducing the reliance on palm-oil-derived surfactants. First, we employ 200 nm-cellulose nanocrystals (CNC) as a reliable model for cotton fibers. CNC enables us to explore interactions among various softener components, including surfactants, guar biopolymers, and fragrances, using physical chemistry techniques applied to bulk dispersions. The primary objec-tive is to elucidate the role of surfactant vesicles, the primary ingredient in textile conditioners, in the association between fragrance capsules and cotton. Secondly, we examine the influence of bi-opolymers present in a newly developed, environmentally friendly softener on this association. Our findings demonstrate that anionic fragrance capsules are deposited onto cotton microfibers in the presence of either cationic surfactants or guar biopolymers, driven by electrostatic interactions. Scanning electron microscopy confirms capsule adsorption on textile fibers when these cationic in-gredients are present. Understanding the interaction mechanisms between fragrance capsules and cotton fabrics, as well as the roles played by other softener components, can facilitate the design of more efficient and sustainable formulations., Comment: 20 pages, 5 figures

Cerium oxide nanoparticles (CNPs) have recently gained increasing interest as redox enzyme-mimetics to scavenge the intracellular excess of reactive oxygen species, including hydrogen peroxide (H2O2). Despite the extensive exploration of CNP scavenging activity, there remains a notable knowledge gap regarding the fundamental mechanism underlying the CNP catalyzed disproportionation of H2O2. In this Letter, we present evidence demonstrating that H2O2 adsorption at CNP surface triggers the formation of stable intermediates known as ceriumperoxo complexes (Ce-O2 2-). The cerium-peroxo complexes can be resolved by Raman scattering and UV-Visible spectroscopy. We further demonstrate that the catalytic reactivity of CNPs in the H2O2 disproportionation reaction increases with the Ce(III) fraction. The developed approach using UV-Visible spectroscopy for the characterization of Ce-O2 2-complexes can potentially serve as a foundation for determining the catalytic reactivity of CNPs in the disproportionation of H2O2.

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 BWNPs 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., Comment: 16 pages, 6 figures

Functional polymers, such as poly(ethylene glycol) (PEG) terminated with a single phosphonic acid, hereafter PEGik-Ph are often applied to coat metal oxide surfaces during post synthesis steps, but are not sufficient to stabilize sub-10 nm particles in protein-rich biofluids. The instability is attributed to the weak binding affinity of post-grafted phosphonic acid groups, resulting in a gradual detachment of the polymers the surface. Here, we assess these polymers as coating agents using an alternative route, namely the one-step wet-chemical synthesis, where PEGik-Ph is introduced with cerium precursors during the synthesis. Characterization of the coated cerium oxide nanoparticles indicates a core-shell structure, where the cores are 3 nm cerium oxide and the shell consists of functionalized PEG polymers in a brush configuration. Results show that cerium oxide nanoparticles coated with PEG1k-Ph and PEG2k-Ph are of potential interest for applications as nanomedicine due to their high Ce(III) content and increased colloidal stability in cell culture media. We further demonstrate that the cerium oxide nanoparticles in the presence of hydrogen peroxide show an additional absorbance band in the UV-vis spectrum, which is attributed to Ce-O22- peroxo-complexes and could be used in the evaluation of their catalytic activity for scavenging reactive oxygen species., Comment: 21 pages, 7 figures

N,N,N-Trimethyl chitosan (TMC), a biocompatible and biodegradable derivative of chitosan, is currently used as a permeation enhancer to increase the translocation of drugs to the bloodstream in the lungs. This article discusses the effect of TMC on a mimetic pulmonary surfactant, Curosurf, a low-viscosity lipid formulation administered to preterm infants with acute respiratory distress syndrome. Curosurf exhibits a strong interaction with TMC, resulting in the formation of aggregates at electrostatic charge stoichiometry. At nanoscale, Curosurf undergoes a profound reorganization of its lipid vesicles in terms of size and lamellarity. The initial micron-sized vesicles (average size 4.8 microns) give way to a froth-like network of unilamellar vesicles about 300 nm in size. Under such conditions, neutralization of the cationic charges by pulmonary surfactant may inhibit TMC permeation enhancer capacity, especially as electrostatic charge complexation is found at low TMC content. The permeation properties of pulmonary surfactant-neutralized TMC should then be evaluated for its applicability as a permeation enhancer for inhalation in the alveolar region., Comment: 20 pages, 7 figures

For applications of pulmonary surfactant delivery to the lungs, the question of rheology of the existing clinical formulations is of upmost importance. Recently, Ciutara and Zasadsinky (Soft Matter, 2021, 17, 5170-5182) measured the rheological properties of Infasurf, Survanta and Curosurf, three of the most used pulmonary surfactant substitutes. This study revealed that these fluids are shear-thinning and characterized by a yield stress. The results obtained by Ciutara et al. on Curosurf differ from our results published in Colloids and Surfaces B: Biointerfaces, 2019, 178, 337-345 and in ACS Nano, 2020, 14, 466 - 475. In contrast, we found that Curosurf suspensions are viscous Newtonian or slightly shear-thinning fluids, with no evidence of yield stress. The purpose of this Comment is to discuss possible causes for the discrepancy between the two studies, and to suggest that for biological fluids such as surfactant substitutes, the microrheology technique of rotational magnetic spectroscopy (MRS) can provide valuable results., Comment: 3 figures, 9 pages

Protein corona formation and nanoparticle aggregation have been heavily discussed over the last years since the lack of fine-mapping of these two combined effects has hindered the targeted delivery evolution and the personalized nanomedicine development. We present a multi-technique approach that combines Dynamic Light and Small-Angle X-ray Scattering techniques with cryo-Transmission Electron Microscopy in a given fashion that efficiently distinguishes protein corona from aggregates formation. This methodology was tested using 25-nm model silica nanoparticles incubated with either model proteins or biologically relevant proteomes (such as fetal bovine serum and human plasma) in buffers of low and high ionic strengths to precisely tune particle-to-protein interactions. In this work, we were able to differentiate protein corona, small aggregates formation, and massive aggregation, as well as obtain fractal information of the aggregates reliably and straightforwardly. The strategy presented here can be expanded to other particle-to-protein mixtures and might be employed as a quality control platform for samples that undergo biological tests., Comment: 14 pages, 6 figures, accepted at ACS Applied Materials and Interfaces

In this feature article, we provide an overview of our research on statistical copolymers as a coating material for metal oxide nanoparticles and surfaces. These copolymers contain functional groups enabling non-covalent binding to oxide surfaces and poly(ethylene glycol) (PEG) polymers for colloidal stability and stealthiness. The functional groups are organic derivatives of phosphorous acid compounds R-H$_2$PO$_3$, also known as phosphonic acids that have been screened for their strong affinity to metals and their ability to build multidentate binding. Herein we develop a polymer-based coating platform that shares features with the techniques of self-assembled monolayers (SAM) and Layer-by-Layer (L-b-L) deposition. The milestones of this endeavor are the synthesis of PEG-based copolymers containing multiple phosphonic acid groups, the implementation of simple protocols combining versatility with high particle production yields and the experimental demonstration of the colloidal stability of the coated particles. As a demonstration, coating studies are conducted on cerium (CeO$_2$), iron ($\gamma$-Fe$_2$O$_3$), aluminum (Al$_2$O$_3$) and titanium (TiO$_2$) oxides of different sizes and morphologies. We finally discuss applications in the domain of nanomaterials and nanomedicine. We evaluate the beneficial effects of coating on redispersible nanopowders, contrast agents for In Vitro/Vivo assays and stimuli-responsive particles., Comment: 28 pages 10 figures, accepted at Langmuir as Invited Feature Article

Inhaled airborne particles smaller than 100 nm entering the airways have been shown to deposit in significant amount in the alveolar region of the lungs. The interior of the alveoli is covered with a ~ 1 micron thick lining fluid, called pulmonary surfactant. Inhaled nanoparticles are susceptible to interact with the lung fluid and modify pulmonary functions. Here we evaluate the structural and rheological properties of the pulmonary surfactant substitute Curosurf which is administered to premature babies for the treatment of respiratory distress syndrome. Curosurf is considered a reliable model of endogenous pulmonary surfactant in terms of composition, structure and function. Using active microrheology based on magnetically actuated wires, we find that Curosurf dispersions exhibit a Newtonian behavior at lipid concentration from 0 to 80 g L-1, and that the viscosity follows the Krieger-Dougherty law observed for a wide variety of colloids. Upon addition of 40 nm alumina nanoplatelets, a significant change of the Curosurf rheology is noticed. The dispersions then enter a soft solid phase characterized by an infinite viscosity and a non-zero equilibrium elastic modulus. The sol-gel transition induced by the nanoparticles is interpreted as the result of the alumina/vesicle interaction, which are illustrated by transmission electron microscopy. It also suggests a potential toxicity associated with the modification of the lung fluid structural and dynamical properties., Comment: 15 pages, 5 figures, 38 references

Fabric conditioners are household products used to impart softness and fragrance to tex-tiles. 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 absence and in 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., Comment: 22 pages, 10 figures, 56 references

We investigate the formation/re-dissociation mechanisms of hybrid complexes made from negatively charged PAA2k coated {\gamma}-Fe2O3 nanoparticles (NP) and positively charged polycations (PDADMAC) in aqueous solution in the regime of very high ionic strength (I). When the building blocks are mixed at large ionic strength (1M NH4Cl), the electrostatic interaction is screened and complexation does not occur. If the ionic strength is then lowered down to a targeted ionic strength Itarget, there is a critical threshold Ic = 0.62 M at which complexation occurs, that is independent on the charge ratio Z and the pathway used to reduce salinity (drop-by-drop mixing or fast mixing). If salt is added back up to 1M, the transition is not reversible and persistent out-of-equilibrium aggregates are formed. The lifetimes of such aggregates depends on Itarget: the closer Itarget to Ic is, the more difficult it is to dissolve the aggregates. Such peculiar behavior is driven by the inner structure of the complexes that are formed after desalting. When Itarget is far below Ic, strong electrostatic interactions induce the formation of dense, compact and frozen aggregates. Such aggregates can only poorly reorganize further on with time, which makes their dissolution upon resalting almost reversible. Conversely, when Itarget is close to Ic more open aggregates are formed due to weaker electrostatic interactions upon desalting. System can thus rearrange with time to lower its free energy and reach more stable out-of-equilibrium states which are very difficult to dissociate back upon resalting, even at very high ionic strength., Comment: 15 pages, 6 figures

Mucus is a viscoelastic gel secreted by the pulmonary epithelium in the tracheobronchial region of the lungs. The coordinated beating of cilia moves mucus upwards towards pharynx, removing inhaled pathogens and particles from the airways. The efficacy of this clearance mechanism depends primarily on the rheological properties of mucus. Here we use magnetic wire based microrheology to study the viscoelastic properties of human mucus collected from human bronchus tubes. The response of wires between 5 and 80 microns in length to a rotating magnetic field is monitored by optical time-lapse microscopy and analyzed using constitutive equations of rheology, including those of Maxwell and Kelvin-Voigt. The static shear viscosity and elastic modulus can be inferred from low frequency (from 0.003 to 30 rad s-1) measurements, leading to the evaluation of the mucin network relaxation time. This relaxation time is found to be widely distributed, from one to several hundred seconds. Mucus is identified as a viscoelastic liquid with an elastic modulus of 2.5 +/- 0.5 Pa and a static viscosity of 100 +/- 40 Pa s. Our work shows that beyond the established spatial variations in rheological properties due to microcavities, mucus exhibits secondary inhomogeneities associated with the relaxation time of the mucin network that may be important for its flow properties., Comment: 19 pages 7 figures

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 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 the technique of magnetic rotational spectroscopy (MRS). In this chapter, we survey this microrheology technique which is 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 dispersion 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., Comment: 19 pages, 7 figures, 4 tables

Research on cerium oxide nanoparticles (nanoceria) has captivated the scientific community due to their unique physical and chemical properties, such as redox activity and oxygen buffering capacity, which made them available for many technical applications, including biomedical applications. The redox mimetic antioxidant properties of nanoceria have been effective in the treatment of many diseases caused by reactive oxygen species (ROS) and reactive nitrogen species. The mechanism of ROS scavenging activity of nanoceria is still elusive, and its redox activity is controversial due to mixed reports in the literature showing pro-oxidant and antioxidant activity. In lieu of its current research interest, it is critical to understand the behaviour of nanoceria in the biological environment and provide answers to some of the critical and open issues. This review critically analyses the status of research on the application of nanoceria to treat diseases caused by ROS. It reviews the proposed mechanism of action and shows the effect of surface coatings on its redox activity. It also discusses some of the crucial issues in deciphering the mechanism and redox activity of nanoceria and suggests areas of future research., Comment: 43 pages; 6 figures; 3 tables

We report the interactions of cationic latex particles synthesized by RAFT/MADIX-mediated emulsion polymerization with anionic cellulose nanocrystals (CNCs) and cotton fabrics. Latexes in the size range 200-300 nm with poly(butyl acrylate) or poly(2-ethylhexyl acrylate) hydropho-bic cores and hydrophilic shell are synthesized. We show that the latex/CNC interaction is me-diated by electrostatics, the interaction being the strongest with the most charged particles. The adsorption process is efficient and does not require any functionalization step for either cellulose or latex. A major result is the observation by cryogenic transmission electron micros-copy of latexes coated with entangled arrays of CNCs, and for the softer particles a notable deformation of their structure into faceted polyhedra. By labeling the latexes with hydrophobic carbocyanine dyes, their deposition on woven cotton fabrics is studied in situ and quantified by fluorescence microscopy. As with the CNCs, the highest deposition on cotton in the wet and dried states is achieved with the most charged latexes. This demonstrates that CNCs can serve as models to adjust the interactions of latex particles with cotton, and thus optimize manufac-turing processes for the development of advanced textiles., Comment: 20 pages 6 figures, to be published in ACS Applied Polymer Materials

Oxidative stress, which is one of the main harmful mechanisms of pathologies including is-chemic stroke, contributes to both neurons and endothelial cell damages, leading to vascular lesions. Although many antioxidants have been tested in preclinical studies, no treatment is currently available for stroke patients. Since cerium oxide nanoparticles (CNPs) exhibit remarkable antioxidant capacities, our objective is to develop an innovative coating to enhance CNPs biocompatibility without disrupting their antioxidant capacities or enhance their toxicity. This study reports the synthesis and characterization of functional polymers and their impact on the enzyme-like catalytic activity of CNPs. To study the toxicity and the antioxidant properties of CNPs for stroke and particularly endothelial damages, in vitro studies are conducted on a cerebral endothelial cell line (bEnd.3). Despite their internalization in bEnd.3 cells, coated CNPs are devoid of cytotoxicity. Microscopy studies report an intracellular localization of CNPs, more precisely in endosomes. All CNPs reduces glutamate-induced intracellular production of ROS in endothelial cells but one CNP significantly reduces both the production of mitochondrial super-oxide anion and DNA oxidation. In vivo studies report a lack of toxicity in mice. This study there-fore describes and identifies biocompatible CNPs with interesting antioxidant properties for ischemic stroke and related pathologies., Comment: 27 pages 9 figures

The combination of multiple functionalities in a single material is an appealing strategy for the de-velopment of smart materials with unique features. In this work, we present the preparation of thermoresponsive magnetic nanoparticles and their one-dimensional assembly into transient micro-filaments. The material is based on 9.4 nm iron oxide nanoparticles grafted with poly(N-n-propylacrylamide) via multiphosphonic acid anchoring sites. The hybrid nanoparticles present a low critical solution temperature (LCST) transition between 21 {\deg}C and 28 {\deg}C, depending on the pH and the ionic strength. When heated above the LCST in defined conditions, the nanoparticles ag-gregate and respond to an external magnetic field. An intrinsic characteristic of the thermorespon-sive particles is an asymmetric transition between cooling and heating cycles, that was favorably exploited to build one-dimensional permanent microstructures, such as magnetic microfilaments and cilia. In summary, we present the development of a nanoplatform responsive to multiple stimu-li, including temperature, magnetic field, pH and ionic strength and its transformation into magneti-cally active microfilaments that could find potential applications in remotely controlled devices., Comment: 18 pages, 8 figures

Concentrated fabric conditioners are water-based formulations containing 10 wt. % of cationic surfactants that are deposited on textile fibers during the rinse cycle in a washing machine to make them smoother and softer to touch. In topical formulations, the concentration of cationic surfactants is reduced by half, this reduction being compensated by the addition of environment-friendly polysaccharides. Using atomic force microscopy (AFM), quartz crystal microbalance with dissipation (QCM-D) and ellipsometry, the deposition of formulations with or without polysaccharides on model cellulose substrates is studied. We found that 180 nm long cellulose nanocrystals (CNCs) deposited by spin-coating on amorphous silicon dioxide or on quartz crystal sensors provide a good model of cellulose surfaces. QCM-D results reveal strong electrostatic interactions of the surfactant vesicles and polysaccharides with the CNC layer. In the presence of polysaccharides, the adsorbed quantities are less (by 60%) than the sum of the respective amounts of each component, the structure of the interface being however more homogenous and rigid. This outcome suggests that surface techniques coupled with CNC coated substrates are promising for studying interactions of current formulations with cellulose surfaces., Comment: 21 pages 5 figures

Bio-inspired materials are commonly used in the development of functional devices. The fabrication of artificial cilia mimicking the biological functions has emerged as a promising strategy for fluid manipulation in miniaturized systems. In this study, we propose a different physicochemical insight for the preparation of magnetic cilia based on the temperature-triggered reversible assembly of coated iron oxide nanoparticles in a bio-compatible template-free approach. The length of the prepared cilia could be tuned between 10 and 100 microns reaching aspect ratios up to 100 in a very dense array of flexible structures with persistence lengths around 8 microns. Magnetic actuation of the cilia revealed robust structures (over several hours of actuation) with a wide range of bending amplitudes resulting from high susceptibility of the filaments. The results demonstrate that the proposed strategy is an efficient and versatile alternative for templated fabrication methods and producing cilia with remarkable characteristics and dimensions within the template-free approaches., Comment: 15 pages 5 figures

Cerium oxide nanoparticles have been shown to mimic oxidoreductase enzymes by catalyzing the decomposition of organic substrates and reactive oxygen species. This mimicry can be found in superoxide radicals and hydrogen peroxides, harmful molecules produced in oxidative stress asso-ciated diseases. Despite the fact that nanoparticle functionalization is mandatory in the context of nanomedicine, the influence of polymer coatings on their enzyme-like catalytic activity is poorly understood. In this work, six polymer coated cerium oxide nanoparticles are prepared by associa-tion of 7.8 nm cerium oxide cores with two poly(sodium acrylate) and four poly(ethylene glycol) (PEG) grafted copolymers with different terminal or anchoring end groups, such as phosphonic acids. The superoxide dismutase-, catalase-, peroxidase- and oxidase-like catalytic activities of the coated nanoparticles were systematically studied. It is shown that the polymer coatings do not af-fect the superoxide dismutase-like, impair the catalase-like and oxidase-like and surprisingly im-proves peroxidase-like catalytic activities of cerium oxide nanoparticles. It is also demonstrated that the particles coated with the PEG-grafted copolymers perform better than the poly(acrylic acid) coated ones as oxidoreductase-like enzymes, a result that confirms the benefit of having phosphon-ic acids as anchoring groups at the particle surface., Comment: 23 pages, 8 figures, 3 tables

Molecular transport of biomolecules plays a pivotal role in the machinery of life. Yet, this role is poorly understood due the lack of quantitative information. Here, the role and properties of the C-terminal region of Escherichia coli Hfq is reported, involved in controlling the flow of a DNA solution. A combination of experimental methodologies has been used to probe the interaction of Hfq with DNA and to measure the rheological properties of the complex. A physical gel with a temperature reversible elasticity modulus is formed due to formation of non-covalent crosslinks. The mechanical response of the complexes shows that they are inhomogeneous soft solids. Our experiments indicate that Hfq C-terminal region could contribute to genome mechanical response. The reported viscoelasticity of the DNA-protein complex might have implications for cellular pro-cesses involving molecular transport of DNA or segments thereof., Comment: 19 pages 5 figures 2 tables

Here we report on the viscosity of eukaryotic living cells as a function of the time, and on the application of stochastic models to analyze its temporal fluctuations. The viscoelastic properties of NIH/3T3 fibroblastic cells are investigated using an active microrheological technique, where magnetic wires, embedded into cells, are being actuated remotely. The data reveal anomalous transient responses characterized by intermittent phases of slow and fast rotation, revealing significant fluctuations. The time dependent viscosity is analyzed from a time series perspective by computing the autocorrelation functions and the variograms, two functions used to describe stochastic processes in mathematical finance. The resulting analysis gives evidence of a sub-diffusive mean-reverting process characterized by an autoregressive coefficient lower than 1. It also shows the existence of specific cellular times in the ranges 1 - 10 s and 100 - 200 s, not previously disclosed. The shorter time is found being related to the internal relaxation time of the cytoplasm. To our knowledge, this is the first time that similarities are established between the properties of time series describing the intracellular metabolism and statistical results from mathematical finance. The current approach could be exploited to reveal hidden features from biological complex systems, or determine new biomarkers of cellular metabolism., Comment: 19 pages, 8 figures, 3 tables

In this study, we investigated the thermodynamic features of a system based on oppositely charged polyelectrolytes, sodium alginate, and poly(diallyldimethylammonium chloride) (PDADMAC) at different pH values. Additionally, a comparison of the effects of the thermodynamic parameters on the growth of the layers based on the same polymers is presented. For this investigation, different techniques were combined to compare results from the association in solution and co-assembled layers at the silicon surface. Dynamic light scattering (DLS) and isothermal titration calorimetry (ITC) were used for studies in solution, and the layer-by-layer technique was employed for the preparation of the polymer layers. Ellipsometry and atomic force microscopy (AFM) were used to characterize the layer thickness growth as a function of the solution pH, and interferometric confocal microscopy was employed to analyze the topography and roughness of the films. The layers grown for the PDADMAC/sodium alginate system demonstrated pH sensitivity with either linear or exponential behavior, depending on the pH values of the polyelectrolyte solutions. The layer thicknesses measured using ellipsometry and AFM data were in good agreement. Additionally, a pH influence on the roughness and topography of the films was observed. Films from basic dipping solutions resulted in surfaces that were more homogeneous with less roughness; in contrast, films with more layers and those formed in a low-pH dipping solution were rougher and less homogeneous., Comment: 30 pages 9 figures, 2 tables

When inhaled nanoparticles (NPs) deposit in alveoli, they transit through the pulmonary surfactant (PS), a biofluid made of proteins and phospholipidic vesicles. They acquire a corona reflecting the PS-nanomaterials 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 raising 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 phospholipidic bilayers surrounding NPs but by multiple hybrid structures derived from NPs-vesicles 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 demonstrate the need of protocols standardization., Comment: 10 pages, 3 figures, 1 scheme, 1 table

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 in the bilayers at different stages of the 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. Based on 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 homecare applications. By means of fluorescence microscopy we then visualize the interaction mechanisms of nanoparticles crossing live cell membranes and of surfactant adsorbing on 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., Comment: 19 pages, 6 figures and 2 schemes, 2 tables

Nanoparticle (NP)-protein complexes exhibit the correct identity of NP in biological media. Therefore, protein-NP interactions should be closely explored to understand and to modulate the nature of NPs in medical implementations. This review focuses mainly on the physicochemical parameters such as dimension, surface chemistry, the morphology of NPs and influence of medium pH on the formation of protein corona and conformational changes of adsorbed proteins by different kinds of methods. Also, the impact of protein corona on the colloidal stability of NPs is discussed. Uncontrolled protein attachment on NPs may bring unwanted impacts such as protein denaturation and aggregation. In contrast, controlled protein adsorption by optimal concentration, size, pH and surface modification of NPs may result in potential implementation of NPs as therapeutic agents especially for disaggregation of amyloid fibrils. Also, the effect of NPs-protein corona on reducing the cytotoxicity and clinical implications such as drug delivery, cancer therapy, imaging and diagnosis will be discussed. Validated correlative physicochemical parameters for NP-protein corona formation frequently derived from protein corona fingerprints of NPs which are more valid than the parameters obtained only on the base of NP features. This review may provide useful information regarding the potency as well as the adverse effects of NPs to predict their behavior in the in vivo experiments., Comment: 40 pages, 20 figures

Particulate air pollution results from different sources, among which those related to road traffic have a significant impact on human health. Combustion-derived particles emitted by thermal engines have been incriminated and are now better controlled. In contrast, non-exhaust emission sources related to car wear and degradation processes are not yet regulated. Here we report on brake wear particles (BWP) harvested in two test facilities operating in France, providing samples from different braking systems and driving/testing conditions. Using a combination of light scattering, X-ray fluorescence, optical and electron microscopy, the particle size and elemental composition are revealed. The BWP are shown to be in the nano- to micrometer range and to have a low carbonaceous content (6%), iron and copper being the main components (> 40%). To evaluate the toxicity potential of its nano-sized fraction, brake wear nanoparticles are isolated by sonication, filtration and ultra-centrifugation techniques, leading to stable colloidal dispersions. A significant outcome of this study is that the nano-sized fraction represents 26% by mass of the initial BWP. Human bronchial epithelial cells (Calu-3) are used as relevant target cells to investigate their cytotoxicity. We observe a clear short-term loss of viability associated to reactive oxygen species generation, but with limited pro-inflammatory effects. On an actual cell-deposited mass-dose basis, the cytotoxicity of the nanosized fraction is similar to that of BWP, suggesting that the cytotoxicity is particle size independent. To conclude, brake wear dust contains substantial amount of metallic nanoparticles exhibiting toxicity for lung cells, and should warrant further consideration., Comment: 27 pages, 4 figures, 11 sections in Supplementary Information, 38 references

We review here different methods to measure the bulk viscosity of complex fluids using micron-sized magnetic wires. The wires are characterized by length of a few microns and diameter of a few hundreds of nanometers. We first draw analogies between cone-and-plate rheometry and wire-based microrheology. In particular we highlight that magnetic wires can be operated as stress-controlled rheometers for two types of testing, the creep-recovery and steady shear experiments. In the context of biophysical applications, the cytoplasm of different cell lines including fibroblasts, epithelial and tumor cells is studied. It reveals that the interior of living cells can be described as a viscoelastic liquid with a static viscosity comprised between 10 and 100 Pas. We extend the previous approaches and show that the proposed technique can also provide time resolved viscosity data, which for cells display strong temporal fluctuations. The present work demonstrates the high potential of the magnetic wires for quantitative rheometry in confined espaces., Comment: 11 pages, 6 figures, 40 references

Recent surveys have shown that the number of nanoparticle-based formulations actually used at the clinical level is significantly lower than expected a decade ago. One reason for this is that the nanoparticle physicochemical properties fall short for handling the complexity of biological environments and for preventing nonspecific protein adsorption. In this study, we address the issue of the interactions of plasma proteins with polymer coated surfaces. To this aim, we use a non-covalent grafting-to method to functionalize iron oxide sub-10 nm nanoparticles and iron oxide flat substrates, and compare their protein responses. The functionalized copolymers consist in alternating poly(ethylene glycol) (PEG) chains and phosphonic acid grafted on the same backbone. Quartz Crystal Microbalance with dissipation was used to monitor the polymer adsorption kinetics and to evaluate the resistance to protein adsorption. On flat substrates, functionalized PEG copolymers adsorb and form a brush in the moderate or in the highly stretched regimes, with density between 0.15 and 1.5 nm-2. PEG layers using phosphonic acid as linkers exhibit excellent protein resistance. In contrast, layers prepared with carboxylic acid as grafting agent exhibit mitigated protein responses and layer destructuration. The present study establishes a correlation between the long-term stability of PEG coated particles in biofluids and the protein resistance of surfaces coated with the same polymers., Comment: 16 pages 8 figures, ACS Omega 2017

Magnetic rotational spectroscopy is based on the use of magnetic micron-size wires for viscosity measurements. Submitted to a rotational magnetic field with increasing frequency, the wires undergo a hydrodynamic instability between a synchronous and an asynchronous regime. From a comparison between predictions and experiments, the static shear viscosity and elastic modulus of wormlike micellar solutions are here determined. The values agree with the determination by cone-and-plate rheometry., Comment: 6 pages, 4 figures, proceedings of the TNT2015 conference in Toulouse

The association processes between engineered TiO2 nanoparticles and Suwannee River humic acids are investigated by isothermal titration calorimetry and by measuring the exchanged heat during binding process allowing the determination of thermodynamic (change of enthalpy, Gibbs free energy and entropy) and reaction (binding affinity constant, reaction stoichiometry) parameters. Our results indicate that strong TiO2-Suwannee River humic acid interactions are entropically and enthalpically favorable with exothermic binding reactions and that the mixing order is also an important parameter. High humic acid concentrations induce homoagglomeration ("self" assembly) and are shown to favor an enthalpically driven association process. Light scattering techniques are also considered to investigate the influence of TiO2 surface charge modifications and agglomeration mechanisms. Patch and bridging mechanisms are found to result into the formation of large agglomerates once charge inversion of TiO2-humic acid complexes is achieved. Moreover van der Waals interactions are also found to play a significant role during interaction processes due to the amphiphilic character of humic acids., Comment: 16 pages, 6 figures. arXiv admin note: text overlap with arXiv:1506.05637

Interaction between engineered nanoparticles and natural organic matter is investigated by measuring the exchanged heat during binding process with isothermal titration calorimetry. TiO2 anatase nanoparticles and alginate are used as engineered nanoparticles and natural organic matter to get an insight into the thermodynamic association properties and mechanisms of adsorption and agglomeration. Changes of enthalpy, entropy and total free energy, reaction stoichiometry and affinity binding constant are determined or calculated at a pH value where the TiO2 nanoparticles surface charge is positive and the alginate exhibits a negative structural charge. Our results indicate that strong TiO2-alginate interactions are essentially entropy driven and enthalpically favorable with exothermic binding reactions. The reaction stoichiometry and entropy gain are also found dependent on the mixing order. Finally correlation is established between the binding enthalpy, the reaction stoichiometry and the zeta potential values determined by electrophoretic mobility measurements. From these results two types of agglomeration mechanisms are proposed depending on the mixing order. Addition of alginate in TiO2 dispersions is found to form agglomerates due to polymer bridging whereas addition of TiO2 in alginate promotes a more individually coating of the nanoparticles., Comment: 30 pages, 6 figures, 11 figures in SI

This study describes the distribution of intravenously injected polyacrylic acid (PAA) coated {\gamma}-Fe2O3 NPs (10 mg kg-1) at the organ, cellular and subcellular levels in healthy BALB/cJ mice and in parallel addresses the effects of NP injection on kidney function, blood pressure and vascular contractility. Magnetic resonance imaging (MRI) and transmission electron microscopy (TEM) showed accumulation of NPs in the liver within 1h after intravenous infusion, accommodated by intracellular uptake in endothelial and Kupffer cells with subsequent intracellular uptake in renal cells, particularly the cytoplasm of the proximal tubule, in podocytes and mesangial cells. The renofunctional effects of NPs were evaluated by arterial acid-base status and measurements of glomerular filtration rate (GFR) after instrumentation with chronically indwelling catheters. Arterial pH was 7.46 and 7.41 in mice 0.5 h after injections of saline or NP, and did not change over the next 12h. In addition, the injections of NP did not affect arterial PCO2 or [HCO3-] either. Twenty-four and 96h after NP injections, the GFR averaged 11.0 and 13.0 ml min-1 g-1, respectively, values which were statistically comparable with controls (14.0 and 14.0 ml min-1 g-1). Mean arterial blood pressure (MAP) decreased 12-24h after NP injections (111 vs 123 min-1) associated with a decreased contractility of small mesenteric arteries revealed by myography to characterise endothelial function. In conclusion, our study demonstrates that accumulation of superparamagnetic iron oxide nanoparticles does not affect kidney function in healthy mice but temporarily decreases blood pressure., Comment: 21 pages, 12 figures, published in Toxicology and Applied Pharmacology 2013

We demonstrate a simple method for rotational microrheology in complex fluids, using micrometric wires. The three-dimensional rotational Brownian motion of the wires suspended in Maxwell fluids is measured from their projection on the focal plane of a microscope. We analyze the mean-squared angular displacement of the wires of length between 1 and 40 microns. The viscoelastic properties of the suspending fluids are extracted from this analysis and found to be in good agreement with macrorheology data. Viscosities of simple and complex fluids between 0.01 and 30 Pa.s could be measured. As for the elastic modulus, values up to ~ 5 Pa could be determined. This simple technique, allowing for a broad range of probed length scales, opens new perspectives in microrheology of heterogeneous materials such as gels, glasses and cells., Comment: to appear in Soft Matter

We report the synthesis of complex salts made from the cationic surfactant dodecyltrimethyl-ammonium and diblock copolymers poly(acrylic acid)-block-poly(acrylamide) of different molecular weights. In water, the complex salts self-assemble into stable hierarchical aggregates with a dense core and a diffuse shell. In contrast to earlier reports, the surfactant/polymer aggregates exhibit a liquid crystalline structure of Pm3n cubic symmetry. The crystal structure is analogous to that obtained with homopolymer. Size and aggregation numbers were estimated from a combination of light and small-angle x-ray scattering experiments. It is found that the size of the aggregates decreases with increasing diblock asymmetry. The complex salt methodology presents many advantages, among which to be insensitive to the preparation conditions and to the mixing pathway., Comment: 16 pages, 7 figures, paper accepted in Langmuir 23-Oct-13

Recent nanotoxicity studies revealed that the physico-chemical characteristics of engineered nanomaterials play an important role in the interactions with living cells. Here, we report on the toxicity and uptake of the iron oxide sub-10 nm nanoparticles by NIH/3T3 mouse fibroblasts. Coating strategies include low-molecular weight ligands (citric acid) and polymers (poly(acrylic acid), MW = 2000 g mol-1). We find that most particles were biocompatible, as exposed cells remained 100% viable relative to controls. The strong uptake shown by the citrate-coated particles is related to the destabilization of the dispersions in the cell culture medium and their sedimentation down to the cell membranes., Comment: 5 pages 3 figures

We report on the uptake, toxicity and degradation of magnetic nanowires by NIH/3T3 mouse fibroblasts. Magnetic nanowires of diameters 200 nm and lengths comprised between 1 {\mu}m and 40 {\mu}m are fabricated by controlled assembly of iron oxide ({\gamma}-Fe2O3) nanoparticles. Using optical and electron microscopy, we show that after 24 h incubation the wires are internalized by the cells and located either in membrane-bound compartments or dispersed in the cytosol. Using fluorescence microscopy, the membrane-bound compartments were identified as late endosomal/lysosomal endosomes labeled with lysosomal associated membrane protein (Lamp1). Toxicity assays evaluating the mitochondrial activity, cell proliferation and production of reactive oxygen species show that the wires do not display acute short-term (< 100 h) toxicity towards the cells. Interestingly, the cells are able to degrade the wires and to transform them into smaller aggregates, even in short time periods (days). This degradation is likely to occur as a consequence of the internal structure of the wires, which is that of a non-covalently bound aggregate. We anticipate that this degradation should prevent long-term asbestos-like toxicity effects related to high aspect ratio morphologies and that these wires represent a promising class of nanomaterials for cell manipulation and microrheology., Comment: 21 pages 12 figures

We propose a simple way to perform three-dimensional (3D) rotational microrheology using two-dimensional (2D) video microscopy. The 3D rotational brownian motion of micrometric wires in a viscous fluid is deduced from their projection on the focal plane of an optical microscope objective. The rotational diffusion coefficient of the wires of length between 1-100 \mu m is extracted, as well as their diameter distribution in good agreement with electron microscopy measurements. This is a promising way to characterize soft visco-elastic materials, and probe the dimensions of anisotropic objects., Comment: 10 pages, 7 Figures, accepted for publication in EPL

The complexation of micelles or charged nanoparticles with neutral-charged block copolymers in aqueous solutions leads to the formation of colloidal superstructures also termed 'colloidal complexes'. Their primary interest relies in their monodispersity in size, and in their increased domain of stability. In this review, the structural characterization by dynamic light scattering, cryo-TEM, and small angle neutron scattering is presented. Small angle neutron scattering results have been analyzed using numerical simulations - Monte Carlo or reverse Monte Carlo (RMC). Such simulations are useful to show the compatibility between different models of colloidal superstructures, and experiment. Our results have allowed us to propose a generic structure of complex colloids, made of a dense core of interacting colloids, bridged by polyelectrolyte blocks, and a hydrated corona. We have shown that such superstructures are formed systematically in these systems, with either micelles or nanoparticles, for different copolymers, and different charges. The text is in French.

In this review, we report recent developments on the shear-induced transitions and instabilities found in surfactant wormlike micelles. The survey focuses on the non-linear shear rheology and covers a broad range of surfactant concentrations, from the dilute to the liquid-crystalline states and including the semi-dilute and concentrated regimes. Based on a systematic analysis of many surfactant systems, the present approach aims to identify the essential features of the transitions. It is suggested that these features define classes of behaviors. The review describes three types of transitions and/or instabilities : the shear-thickening found in the dilute regime, the shear-banding which is linked in some systems to the isotropic-to-nematic transition, and the flow-aligning and tumbling instabilities characteristic of nematic structures. In these three classes of behaviors, the shear-induced transitions are the result of a coupling between the internal structure of the fluid and the flow, resulting in a new mesoscopic organization under shear. This survey finally highlights the potential use of wormlike micelles as model systems for complex fluids and for applications., Comment: 64 pages, 31 figures, 2 tables

The elaboration of multimodal nanoparticles stimulates tremendous interest owing to their numerous potentialities in many applicative fields like optoelectronics, photonics and especially bioimaging. The concomitant association of various properties (optical, electrochemical, magnetic) allows for the use of complementary stimuli in order to probe the interactions between the nanoparticles and their surroundings.Nanoparticles (NPs) have thus become highly praised tools to image cells and tissues with a large contrast compatible with the dimensions of biological materials and the existence of quantum confinement effects induced by the reduced dimensions. In this context, the combination of magnetism and emissive properties such as fluorescence appears particularly attractive for non-invasive investigations, cell sorting or drug vectorization. Therefore, combining both fluorescence and magnetism requires the delicate construction of hybrid assemblies. Most of the magnetic nanoparticles are made of metallic oxides or alloys, e.g. gamma-Fe2O3, Fe3O4, FePt, while the target fluorescent entities are often organic dyes or quantum dots (QDs)., Comment: 9 figures, 1 table, 7 pages - to appear in Small 2009