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Giant unilamellar vesicles (GUVs) are widely used minimal cell models where essential biological features can be reproduced, isolated and studied. Although precise spatio-temporal distribution of membrane domains is a process of crucial importance in living cells, it is still highly challenging to generate anisotropic GUVs with domains at user-defined positions. Here we describe a novel and robust method to control the spatial position of lipid domains of liquid-ordered (Lo) / liquid-disordered (Ld) phase in giant unilamellar vesicles (GUVs). Our strategy consists in confining Lo/Ld phase-separated GUVs in microfluidic channels to define free budding regions where the minority phase lipid domains localize and grow by decreasing the line tension between the co-existing phases. We show that this process is governed by the respective fraction of the two phases, and not by the chemical nature of the lipids involved. The spatial position and number of domains are controlled by the design of the confining microchannel and could result in polarized GUVs with a controllable number of poles. The developed method is versatile and user-friendly, while allowing to perform multiple single-vesicle experiments in parallel.

International audience; Hybrid DNA-protein nanogels represent potential protein vectors and enzymatic nanoreactors for modern biotechnology. Here, we describe a new, easy, and robust method for preparation of tunable DNA-protein nanogels with controllable size and density. For this purpose, polymerase chain reaction is used to prepare highly biotinylated DNA as a soft biopolymeric backbone, which can be efficiently cross-linked via streptavidin-biotin binding. This approach enables us to control both the density and size of the resulting nanogels not only by adjusting the amount of the cross-linking streptavidin but also by using different rates of DNA biotinylation. This gives DNA-streptavidin nanogels with the size ranging from 80 nm, for the most compact state, to up to 200 nm. Furthermore, using streptavidin-enzyme conjugates allows the straightforward one-pot incorporation of enzymes during the preparation of the nanogels. Monoenzymatic and multienzymatic nanogels have been obtained in this manner, and their catalytic activities have been characterized. All tested enzymes (alkaline phosphatase (AP), horseradish peroxidase (HRP), and β-galactosidase (βGal)), incorporated individually or in a coupled manner (glucose oxidase (GOx)-HRP cascade), were shown to remain functional. The activities of AP and βGal were unchanged while that of HRP was slightly improved inside the nanogels. We demonstrate that, for HRP, it is not the DNA-to-enzyme ratio but the physical density of the functionalized DNA nanogels that is responsible for the improvement of its enzymatic activity.

Based on the remarkably specific antibody-antigen interaction, immunoassays have emerged as indispensable bioanalytical tools for both fundamental research and biomedical applications but necessitate long preliminary steps for the selection, production and purification of the antibody(ies) to be used. Here, we adopt a paradigm shift exploring the concept of creating a rapid and purification-free assay where the antibody is replaced by its coding DNA as a starting material, while exploiting a drop microfluidic format to dramatically decrease sample volume and accelerate throughput and sorting capability. The methodology consists in the co-encapsulation of a DNA coding for the variable domain of the heavy chain of heavy-chain only antibodies (VHH), a reconstituted cell-free expression medium, the target antigen and a capture scaffold where VHH:antigen accumulate to create a detectable signal, inside picoliter drop compartments. We first demonstrate successful synthesis of a functional hemagglutinin (HA)-tagged anti-GFP VHH, referred to as NanoGFP, at a high yield (15.3 ± 2.0 µg·mL-1) in bulk and in less than 3 h using PURExpress cell-free expression medium. We then use a microfluidic device to generate stable water-in-oil drops (30 pL) encapsulating NanoGFP-coding DNA, PURExpress medium, EGFP antigen and HA tag-specific magnetic nanoparticles prior to incubating at 37 °C the resulting emulsion under a magnetic field, inducing both in situ synthesis of NanoGFP and accumulation of NanoGFP:EGFP complexes on magnetically assembled particles. This allows us to assess, for the first time and in less than 3 hours, the binding of an antigen to a cell-free synthesized antibody, in a large number of picoliter drops down to a DNA concentration as low as 12 plasmids per drop. We also show that the drops of this immunoassay can be further sequentially analyzed at high throughput (500 Hz), thus offering capability for library screening, sorting and/or rare event detection. We finally demonstrate the versatility of this method by using DNA coding for different VHH (e.g., anti-mCherry protein), by characterizing VHH specificity in the presence of antigen mixtures, and by showing that antigens can be either inherently fluorescent or not. We thus anticipate that the ultraminiaturized format (pL), rapidity (3 h), programmability (DNA-encoded approach) and versatility of this novel immunoassay concept will constitute valuable assets for faster discovery, better understanding and/or expanded applications of antibodies.

Background Opioid-free anesthesia (OFA) is a new method of anesthesia based on a paradigm shift. Under general anesthesia, the physiology and/or the pathophysiological variations clinically observed are more a reflection of a systemic reaction to the stress (surgical and anesthesia stresses) than a true reflection of pain. Objective To report the results of a large monocenter, retrospective, non-interventional observational study of all consecutive patients who received a total intravenous (IV)-OFA protocol for the surgical management of major open abdominal and urological surgery. Patients and Methods We retrospectively extracted the anesthesia files of 311 consecutive patients (regional anesthesia excluded). No opioids were administered to any of these patients during the surgery. IV morphine administered in the recovery room was the primary endpoint of the study. The secondary endpoints included the amount of opioid required during the first two postoperative days, as well as the maximum pain intensity. Results Only very small doses of IV morphine were administered. The mean total morphine titration was 2 mg (1.9 ± 2.9 mg), corresponding to control of the maximal level of pain to 2.1 ± 2.6 as evaluated with a numerical scale in the postoperative care unit. Similarly, we observed a very low level of morphine consumption during the first two postoperative days. Conclusions These results highlight the safety and the feasibility of our total IV-OFA protocol, thus confirming this new paradigm. Under general anesthesia, the cardiovascular and inflammatory response to the stress could be reliably managed through a multimodal approach without a need for opioids. In the postoperative period, very low doses of opioids were required. Electronic supplementary material The online version of this article (10.1007/s40801-020-00218-3) contains supplementary material, which is available to authorized users.

The text proposes a protocol for a scoping review to explore what culturally safe forensic mental health services look like, identify its key components, and the best practices for implementation. The review aims to answer these two questions: What do we know about what culturally safe forensic mental health services may or should look like? How can culturally safe forensic mental health services be implemented? A Qualitative Framework Synthesis method, using the Indigenous Allied Health Association Cultural Responsiveness Capability Framework, will be used to conduct data analysis, which emphasizes the knowing, the being, and the doing, both at the individual and the organisational level.

Self-assembly is both an advantageously spontaneous process to organize molecular or colloidal entities into synthetic functional superstructures and a key-feature of how life builds its components. However, compared to their living counterparts, synthetic materials made by self-assembly usually lack some of the interesting properties of living systems such as multicomponent character or capability to adapt, transform and evolve. Here we describe an isothermal multicomponent DNA self-assembly method that recapitulates all these characteristics and leads to user-defined objects with programmable shape, site-specific function, intrinsic reconfigurability and unprecedented capacity of major transformation and shape evolution. Using a generic magnesium-free buffer containing NaCl, we show that a complex cocktail of hundreds of different DNA strands can spontaneously assemble at room or body temperature to form desired DNA origamis of various shapes with site-specific protein functionalization, extended nanogrids or single-strand tile-assemblies. In situ atomic force microscopy allows us to follow the self-assembly process and demonstrate that DNA origami assembly proceeds through multiple folding pathways, the system escaping kinetic traps until it reaches its equilibrium target structure. We also show that, under thermodynamic control, this method allows a given system to self-select its most stable shape in a large pool of competitive DNA strands. We finally demonstrate the first giant morphological transformation of DNA origamis spontaneously evolving at constant temperature from one shape to a radically different one by the massive exchange of all its constitutive staple strands. This method greatly expands the repertoire of shapes and functions attainable by isothermal self-assembly as well as provides tools to design evolutive DNA assemblies, with applications ranging from directed or self-adaptive morphological changes to nanostructure optimization by evolution.

International audience; Self-propelled drops are capable of motion without external intervention. As such, they constitute attractive entities for fundamental investigations in active soft matter, hydrodynamics, and surface sciences, as well as promising systems for autonomous microfluidic operations. In contrast with most of the examples relying on organic drops or specifically treated substrates, here we describe the first system of nonreactive water drops in air that can propel themselves on a commercially available ordinary glass substrate that was used as received. This is achieved by exploiting the dynamic adsorption behavior of common n-alkyltrimethylammonium bromide (C n TAB) surfactants added to the drop. We precisely analyze the drop motion for a broad series of surfactants carrying n = 6 to 18 carbon atoms in their tail and establish how the motion characteristics (speed, probability of motion) are tuned by both the hydrophobicity and the concentration of the surfactant. We show that motion occurs regardless of the n value but only in a specific concentration range with a maximum speed at around one tenth of the critical micelle concentration (CMC/10) for most of the tested surfactants. Surfactants of intermediate hydrophobicity are shown to be the best candidates to power drops that can move at a high speed (1−10 cm s −1), the optimal performance being reached with [C 12 TAB] = 800 μM. We propose a mechanism where the motion originates from the anisotropic wettability of the substrate created by the electrostatic adsorption of surfactants beneath the moving drop. Simply drawing lines with a marker pen allows us to create guiding paths for drop motion and to achieve operations such as complex trajectory control, programmed drop fusion, drop refilling, as well as drop moving vertically against gravity. This work revisits the role of surfactants in dynamic wetting and self-propelled motion as well as brings an original strategy to build the future of microfluidics with lower-cost, simpler, and more autonomous portable devices that could be made available to everyone and everywhere.

International audience; Programmable DNA base pairing is a powerful way to build user-defined nanostructured assemblies, such as DNA origamis and DNA nanogrids. Although two-dimensional (2D) origamis of virtually any desired shape can now be quickly and easily produced, attaining further levels of organization, actuation or dynamics is still a desired challenge. Here we report that, upon adsorption on a soft cationic substrate prepared by layer-by-layer deposition of polyelectrolytes, both 2D origamis and DNA nanogrids undergo a rapid higher-order transition of folding into threedimensional (3D) compact structures (origamis) or well-defined µmlong ribbons (nanogrids), a process we refer to as supra-folding. We show that the supra-folding mechanism is mainly of electrostatic nature through on-surface inter-polyelectrolyte complexation, thus requiring enough fuzziness of the substrate to allow 3D reconfiguration instead of conventional flat adsorption. Interestingly the electrostatic nature of this actuation makes it reversible: once supra-folded, origamis can be switched back on the surface into their 2D original shape through addition of heparin, a highly charged anionic polyelectrolyte known as an efficient competitor of DNApolyelectrolyte complexation. Orthogonal to DNA base-pairing principles, this reversible structural reconfiguration is also versatile; we show in particular that i) it is compatible with various origami shapes, ii) it perfectly preserves fine structural details as well as sitespecific functionality, and iii) it can be applied to dynamically address the spatial distribution of origami-tethered proteins.

International audience; Optically addressable colloidal assembly at fluid interfaces is a highly desired component to generate reconfigurable 2D materials, but has rarely been achieved and only with specific interface engineering. Here we describe a generic method to get optically reconfigurable colloidal crystals at the air/water interface and emphasize a new mechanism to convert light into tunable lattice properties. We use light-absorbing anionic particles adsorbed at the air/water interface in the presence of minute amounts of cationic surfactant, which self-assembled into closely-packed polycrystalline structures by collectively deforming the surrounding interface. Low-intensity irradiation of these colloidal crystals results in unprecedented control of the interparticle spacing (IPS) in a preserved crystalline state while, at a higher intensity, cycles of melting/recrystallization with a controllable transition kinetics can be achieved upon successive on/off stimulations. We show that this photoreversible melting originates from an initial thermocapillary stress, expanding the colloidal assembly against the local confinement, and an increase in particles diffusivity imposing the transition kinetics. With this mechanism, local irradiation leads to highly dynamic patterns, including self-healing or self-fed "living" crystals, while multi-responsive assembly is also achieved by controlling particle organization with both light and magnetic stimuli.

The “flipping method” is a new straightforward way to both adsorb and organize microparticles at a liquid interface, with ultralow amounts of a surfactant and no other external forces than gravity. Here we demonstrate that it allows the adsorption of a variety of inorganic nanoparticles at an air/water interface, in an organized way, which is directly controlled by the surfactant concentration, ranging from amorphous to highly crystalline two-dimensional assemblies. With micromolar amounts of a conventional cationic surfactant (dodecyltrimethylammonium bromide, DTAB), nanoparticles of different compositions (silica, silver, and gold), sizes (down to 100 nm) and shapes (spheres and cubes) adsorb from the bulk and directly organize at the air/water interface, resulting in marked optical properties such as reflectivity or intense structural coloration.

International audience; The so-called coffee-ring effect (CRE) is extraordinarily common, problematic in industry and attractively puzzling for researchers, with the accepted rule that it requires two key-ingredients: solvent evaporation and contact line pinning. Here, we demonstrate that the CRE also occurs when the solvent of a pinned sessile drop transfers into another liquid, without involving any evaporation. We show that it shares all characteristic features of the evaporative CRE: solvent transfer-driven transport of solutes to the contact line, ring-shaped deposit, closely-packed particle organization at the contact line, and sizedependent particle sorting. We thus suggest expanding the definition of the coffee-ring effect to any pinned drop having its solvent transferring to an outer medium where the drop compounds cannot be dissolved.

International audience; Control over particle interactions and organization at liquid interfaces is of great importance both for fundamental studies and practical applications. Rendering these systems stimulus-responsive is thus a desired challenge both for investigating dynamic phenomena and realizing reconfigura-ble materials. Here, we describe the first reversible photo-control of two-dimensional colloidal crystallization at the air/ water interface, where millimeter-sized assemblies of micro-particles can be actuated through the dynamic adsorption/ desorption behavior of a photosensitive surfactant added to the suspension. This allows us to dynamically switch the particle organization between a highly crystalline (under light) and a disordered (in the dark) phase with a fast response time (crystallization in % 10 s, disassembly in % 1 min). These results evidence a new kind of dissipative system where the crystalline state can be maintained only upon energy supply.

International audience; Liquid marbles, that is, liquid drops coated by a hydrophobic powder, do not wet any solid or liquid substrate, making their transport and manipulation both highly desirable and challenging. Herein, we describe the light driven transport of floating liquid marbles and emphasize a surprising motion behavior. Liquid marbles are deposited on a water solution containing photosensitive surfactants. Irradiation of the solution generates photoreversible Marangoni flows that transport the liquid marbles toward UV light and away from blue light when the thickness of the liquid substrate is large enough (Marangoni regime). Below a critical thickness, the liquid marbles move in the opposite direction to that of the surface flow at a speed increasing with decreasing liquid thickness (anti Marangoni). We demonstrate that the anti Marangoni motion is driven by the free surface deformation, which propels the non-wetting marble against the surface flow. We call this behavior "slide effect".

International audience; We precisely measure the effect of moderate magnetic field intensity on the surface tension of liquids, by placing pendant drops inside uniform fields where bulk forces due to gradients are eliminated. The surface tension of water is unaffected while that of paramagnetic salt solutions slightly decreases with increasing field strength.

International audience; Self-assembled nucleobases, such as G-quartets or quadruplexes, have numerous applications, but light-responsive structures are limited to small, noncrystalline motifs. In addition, the assembly of the widely exploited azobenzene photochromic compounds can produce fluorescent crystals of extended dimensions but at the prize of sacrificing their photoswitchability. Here, we overcome inherent limitations of self-assembly with a new concept of supramolecular coassembly leading to materials with unprecedented properties. We show that the coassembly of guanosine monophosphate (GMP) with an azobenzene-containing DNA intercalator produces supramolecular crystals arranged through a combination of π–π, electrostatic, and hydrogen-bond interactions. The resulting crystals are 100 μm long, pH-sensitive, fluorescent, and can be photoreversibly disassembled/reassembled upon UV/blue irradiation. This allows us to perform operations such as dynamic photocontrol of a single-crystal growth, light-gated permeability in membrane-like materials, and photoswitchable fluorescence. We believe this concept critically expands the breadth of multifunctional materials attainable by self-assembly.

Opioid-free anesthesia (OFA) is more than a new anesthesia practice. It is indeed a true paradigm shift based on the concept that, under general anesthesia (GA), there is no real pain but rather a cardiovascular reaction to surgical and anesthesia stress. We retrospectively recorded data (2015-2018) from patients who underwent long-duration open abdominal surgery using a total intravenous (IV) OFA (i.e. without epidural or other regional anesthesia or local anesthetic infiltration). This study included consecutively 311 patients. No opioids were administered during surgery to any of these patients. IV morphine administered in the recovery room (PACU) was the primary endpoint of the study. Only very small doses of IV morphine were administered. The mean morphine titration was 2 mg (1.9 +/- 2.9 mg) corresponding of control maximal level of pain 2.1 +/- 2.67 evaluated with numerical scale (NRS) in PACU. Similar results were observed during the two postoperative days. These results confirmed the safety and efficacy of our total IV OFA protocol. Overall, this data confirmed the proposed paradigm. Under GA, a control of cardiovascular and inflammatory response to the stress could be reliably obtained through a multimodal approach without the need of opioids. In the postoperative period, very low doses of opioids were required. These promising results may hopefully lead to a decreased incidence of postoperative persistent pain as well as a decreased risk of tumor recurrence and metastasis. Funding Statement: The authors stated: "None." Declaration of Interests: The authors stated: "None." Ethics Approval Statement: The study was approved by our National Ethic committee (Comite d’Ethique en Anesthesie Reanimation = CERAR, Pr. Jean Etienne Bazin; IRB number 00010254-2016-0007).

We study the effect of surfactants on the deposits formed after the evaporation of colloidal suspension drops, at initial concentrations lower than the critical micellar concentrations, for various particle/surfactant mixtures. We show that the surfactant-mediated interactions between particles and the liquid-gas (LG) and liquid-solid (LS) interfaces, rather than the flow patterns, primarily define the morphology of the dry deposit in a robust and reproducible manner. For like-charged particle/surfactant mixtures, most of the particles form a ring-shaped deposit (according to the so-called "Coffee-Ring Effect"), but some particles can also be deposited inside the ring in a way that is modulated by electrostatic interactions between the particles and the LS interface. For oppositely charged systems, surfactant adsorption to the particle surface strongly affects particle-LG interface interactions, which in turn control the deposition pattern. For low surfactant concentrations, coffee-rings are systematically observed. For intermediate concentrations, the charge of surfactant-decorated particles becomes nearly neutral, and their hydrophobicity is enhanced, which promotes particle trapping at the LG interface. A particle skin is formed and its deposition upon drying leads to homogeneous disk-like patterns. For high surfactant concentrations, particle charge is reversed, and coffee-rings are observed again. Notably, this ring-disk-ring evolution of the deposition behavior as a function of surfactant concentration is observed in a variety of mixtures, regardless of particle absolute charge and surface chemistry as well as of surfactant charge and hydrophobicity. Its apparent universal character makes it a promising strategy for a robust control of particle deposition from evaporating drops.

International audience; We have recently devised the evaporative optical Marangoni assembly (eOMA), a novel and versatile interfacial flow-based method for directing the deposition of colloidal nanoparticles (NPs) on solid substrates from evaporating sessile drops along desired patterns using shaped UV light. Here, we focus on a fixed UV spot irradiation resulting in a cylinder-like deposit of assembled particles and show how the geometrical features of the single deposit can be tailored in three dimensions by simply adjusting the optical conditions or the sample composition, in a quantitative and reproducible manner. Sessile drops containing cationic NPs and a photosensitive surfactant at various concentrations are allowed to evaporate under a single UV beam with a diameter much smaller than that of the drop. After complete evaporation, the geometrical characteristics of the NP deposits are precisely assessed using optical profilometry. We show that both the volume and the radial size of the light-directed NP deposit can be adjusted by varying the diameter or the intensity of the UV beam or alternatively by changing the concentration of the photosensitive surfactant. Notably, in all these cases, the deposits display an almost constant median height corresponding to a few layers of particles. Moreover, both the radial and the axial extent of the patterns are tuned by changing the NP concentration. These results are explained by the correlation among the strength of Marangoni flow, the particle trapping efficiency, and the volume of the deposit, and by the role of evaporation-driven flow in strongly controlling the deposit height. Finally, we extend the versatility of eOMA by demonstrating that NPs down to 30 nm in diameter can be effectively patterned on glass or polymeric substrates.

DNA micro- and nanogels—small-sized hydrogels made of a crosslinked DNA backbone—constitute new promising materials, but their functions have mainly been limited to those brought by DNA. Here a new way is described to prepare sub-micrometer-sized DNA gels of controllable crosslinking density that are able to embed novel functions, such as an enzymatic activity. It consists of using proteins, instead of traditional base-pairing assembly or covalent approaches, to form crosslinks inside individual DNA molecules, resulting in structures referred to as intramolecularly protein-crosslinked DNA gels (IPDGs). It is first shown that the addition of streptavidin to biotinylated T4DNA results in the successful formation of thermally stable IPDGs with a controllable crosslinking density, forming structures ranging from elongated to raspberry-shaped and pearl-necklace-like morphologies. Using reversible DNA condensation strategies, this paper shows that the gels can be reversibly actuated at a low crosslinking density, or further stabilized when they are highly crosslinked. Finally, by using streptavidin–protein conjugates, IPDGs with various enzymes are successfully functionalized. It is demonstrated that the enzymes keep their catalytic activity upon their incorporation into the gels, opening perspectives ranging from biotechnologies (e.g., enzyme manipulation) to nanomedicine (e.g., vectorization).

International audience; The magnetic actuation of deposited drops has mainly relied on volume forces exerted on the liquid to be transported, which is poorly efficient with conventional diamagnetic liquids such as water and oil, unless magneto-sensitive particles are added. Herein, we describe a new and additive-free way to magnetically control the motion of discrete liquid entities. Our strategy consists of using a paramagnetic liquid as a deformable substrate to direct, using a magnet, the motion of various floating liquid entities, ranging from naked drops to liquid marbles. A broad variety of liquids, including diamagnetic (water, oil) and nonmagnetic ones, can be efficiently transported using the moderate magnetic field (ca. 50 mT) produced by a small permanent magnet. Complex trajectories can be achieved in a reliable manner and multi-plexing potential is demonstrated through on-demand drop fusion. Our paramagnetofluidic method advantageously works without any complex equipment or electric power, in phase with the necessary development of robust and low-cost analytical and diagnostic fluidic devices.

France still remembers well the major flood which happened in 1910 and the dramatic damages it created at that time. Today with 17 million people and nine million jobs potentially impacted by the key rivers floods, France is very exposed to flooding hazards and particularly the Paris and the Ile de France Basin. Several EU Member States share similar significant flood risk and experienced, indeed, in UK,Germany and Central Europe very large floodings creating several Billion Euro of damages and a significant number of casualties. The recognition of this important flood risk across many EU Member countries led to the establishment of the October 2007, European Directive which provided a general framework for public management of floods. And Member States were required to incorporate this Directive into national law by 2010.To benefit from its International competences a Review of Risk Management Policies was conducted by the OECD Directoriate for Public Governance and Territorial Development.This review was supported by the French Ministry of Ecology, Sustainable Development and Energy and EU and led to a very comprehensive report published in 2014 providing a set of important recommendations on: governance of flood risk, on increasing resilience and on financing prevention. Based on the 2010 French law and helped by the recommendations of the OECD report the French government launched a National Flood Risk Management Strategy associating all flood management parties through the Joint Flood Commission (CMI). After a national public consultation the project of national strategy has been adopted on the 7th October 2014 by the Ministers of Environment, Interior, Agriculture and Housing. This document is the basis of the French Flood Management Policy at national, district, basin and local levels and actions plans have been devolopped accordingly over the whole country..To test the effectiveness of the Policies and actions put in place the Secretary General of the Paris Defense and Safety Zone (SGZDS) covering the whole Ile-de-France area organized an exercise simulating major Seine flooding in Ile-de-France basin.This exercise called EU SEQUANA lasted two whole weeks in 2016, March 7th–March 18th. More than 90 national and EU partners were involved in this project, most of them from vital importance sectors such as energy,water, transport, telecommunications….

International audience; The coffee-ring effect denotes the accumulation of particles at the edge of an evaporating sessile drop pinned on a substrate. Because it can be detected by simple visual inspection, this ubiquitous phenomenon can be envisioned as a robust and cost-effective diagnostic tool. Toward this direction, here we systematically analyze the deposit morphology of drying drops containing polystyrene particles of different surface properties with various proteins (bovine serum albumin (BSA) and different forms of hemoglobin). We show that deposit patterns reveal information on both the adsorption of proteins onto particles and their reorganization following adsorption. By combining pattern analysis with adsorption isotherm and zeta potential measurements, we show that the suppression of the coffee-ring effect and the formation of a disk-shaped pattern is primarily associated with particle neutralization by protein adsorption. However, our findings also suggest that protein reorganization following adsorption can dramatically invert this tendency. Exposure of hydrophobic (respectively charged) residues can lead to disk (respectively ring) deposit morphologies independently of the global particle charge. Surface tension measurements and microscopic observations of the evaporating drops show that the determinant factor of the deposit morphology is the accumulation of particles at the liquid/ gas interface during evaporation. This general behavior opens the possibility to probe protein adsorption and reorganization on particles by the analysis of the deposit patterns, the formation of a disk being the robust signature of particles rendered hydrophobic by protein adsorption. We show that this method is sensitive enough to detect a single point mutation in a protein, as demonstrated here by the distinct patterns formed by human native hemoglobin h-HbA and its mutant form h-HbS, which is responsible for sickle cell anemia.

Synthetic gene circuits are emerging as a versatile means to target cancer with enhanced specificity by combinatorial integration of multiple expression markers. Such circuits must also be tuned to be highly sensitive because escape of even a few cells might be detrimental. However, the error rates of decision-making circuits in light of cellular variability in gene expression have so far remained unexplored. Here, we measure the single-cell response function of a tunable logic AND gate acting on two promoters in heterogeneous cell populations. Our analysis reveals an inherent tradeoff between specificity and sensitivity that is controlled by the AND gate amplification gain and activation threshold. We implement a tumor-mimicking cell-culture model of cancer cells emerging in a background of normal ones, and show that molecular parameters of the synthetic circuits control specificity and sensitivity in a killing assay. This suggests that, beyond the inherent tradeoff, synthetic circuits operating in a heterogeneous environment could be optimized to efficiently target malignant state with minimal loss of specificity.

The OECD report “Boosting Resilience through Innovative Risk Governance” examines the efforts of OECD countries to prevent or reduce future disaster impacts, and highlights several key areas where improvements can be made. International collaboration is insufficiently utilised to address shocks that have increasingly global consequences. Institutional design plays a significant role in facilitating or hampering the engagement and investments of governmental and non-governmental stakeholders in disaster risk prevention and mitigation. To inform the design of “better” institutions, the OECD proposes the application of a diagnostic framework that helps governments identify institutional shortcomings and take actions to improve them. The goal of the case study on the Rhone River is to conduct an analysis of the progress, achievements and existing challenges in designing and implementing disaster risk reduction strategies through the Rhone Plan from a comparative perspective across a set of selected countries of this study, like Austria and Switzerland, will inform how to improve institutional frameworks governing risk prevention and mitigation. The case study will be used to identify examples of successful practice taking into account their specific country contexts, and analyse their potential for policy transfer.

With 17, 1 million people and 9 million jobs exposed to river flood, 1, 4 million people and over 850 000 jobs exposed to flood from the sea, France is very exposed to flood hazards. To face this issue, French government launches a National Flood Risk Management Strategy associating all flood management parties through the Joint Flood Commission (CMI). After a national public consultation the project of national strategy has been adopted on the 7th October 2014 by the Ministers of Environment, Interior, Agriculture and Housing. This document is the basis of the French Flood Management Policy at national, district, basin and local level.

International audience; External control of DNA melting and hybridization, a key step in bio- and DNA nanotechnology, is commonly achieved with temperature. The use of light to direct this process is a challenging alternative, which has been only possible with a DNA modification, such as covalent grafting or mismatch introduction, so far. Here we describe the first photocontrol of DNA melting that relies on the addition of a molecule that noncovalently interacts with unmodified DNA and affects its melting properties in a photoreversible and highly robust manner, without any prerequisite in the length or sequence of the target DNA molecule. We synthesize azobenzene-containing guanidinium derivatives and show that a bivalent molecule with a conformation-dependent binding mode, AzoDiGua, strongly increases the melting temperature (Tm) of DNA under dark conditions because its trans isomer intercalates in the DNA double helix. Upon UV irradiation at 365 nm, the trans–cis isomerization induced the ejection of AzoDiGua from the intercalation binding sites, resulting in a decrease in Tm up to 18 °C. This illumination-dependent Tm shift is observed on many types of DNA, from self-complementary single-stranded or double-stranded oligonucleotides to long genomic duplex DNA molecules. Finally, we show that simply adding AzoDiGua allows us to photoreversibly control the assembly/disassembly of a DNA nanostructure at constant temperature, as demonstrated here with a self-hybridized DNA hairpin. We anticipate that this strategy will be the key ingredient in a new and generic way of placing DNA-based bio- and nanotechnologies under dynamic control by light.

Controlled particle deposition on surfaces is crucial for both exploiting collective properties of particles and their integration into devices. Most available methods depend on intrinsic properties of either the substrate or the particles to be deposited making them difficult to apply to complex, naturally occurring or industrial formulations. Here we describe a new strategy to pattern particles from an evaporating drop, regardless of inherent particle characteristics and suspension composition. We use light to generate Marangoni surface stresses resulting in flow patterns that accumulate particles at predefined positions. Using projected images, we generate a broad variety of complex patterns, including multiple spots, lines and letters. Strikingly, this method, which we call evaporative optical Marangoni assembly (eOMA), allows us to pattern particles regardless of their size or surface properties, in model suspensions as well as in complex, real-world formulations such as commercial coffee.

Difficulties in culturing cells inside microchannels is a major obstacle for the wide use of microfluidic technology in cell biology. Here, we present a simple and versatile method to interface closed microchannels with cellular and multicellular systems. Our approach, based on microfluidic stickers which can adhere to wet glass coverslips, eliminates the need to adapt cell culture conditions to microchannels and greatly facilitates the methods required to position cells into microcircuits. We demonstrate the simplicity and efficiency of the method with HeLa cells, primary cultured neurons and Drosophila tissues.

In this paper we first introduce a novel fabrication process, which allows for easy integration of thin track-etched nanoporous membranes, within 2D or 3D microchannel networks. In these networks, soluble chemical compounds can diffuse out of the channels through well-defined and spatially organized microfabricated porous openings. Interestingly, multiple micron-scale porous areas can be integrated in the same device and each of these areas can be connected to a different microfluidic channel and reservoir. We then present and characterize several membrane-based microdevices and their use for the generation of stable diffusible concentration gradients and complex dynamic chemical landscapes under shear free conditions. We also demonstrate how a simple flow-focusing geometry can be used to generate “on-demand” concentration profiles. In turn, these devices should provide an ideal experimental framework for high throughput cell-based assays: long term high-resolution video microscopy experiments can be performed, under multiple spatially and temporally controlled chemical conditions, with simple protocols and in a cell-friendly environment.

International audience; Nerve growth cones (GCs) are chemical sensors that convert graded extracellular cues into oriented axonal motion. To ensure a sensitive and robust response to directional signals in complex and dynamic chemical landscapes, GCs are presumably able to amplify and filter external information. How these processing tasks are performed remains however poorly known. Here, we probe the signal-processing capabilities of single GCs during ?-Aminobutyric acid (GABA) directional sensing with a shear-free microfluidic assay that enables systematic measurements of the GC output response to variable input gradients. By measuring at the single molecule level the polarization of GABA A chemoreceptors at the GC membrane, as a function of the external GABA gradient, we find that GCs act as i), signal amplifiers over a narrow range of concentrations, and ii), low-pass temporal filters with a cutoff frequency independent of stimuli conditions. With computational modeling, we determine that these systems-level properties arise at a molecular level from the saturable occupancy response and the lateral dynamics of GABA A receptors. Cop. 2012 Biophysical Society.

Fundamental and applied biomedical research increasingly relies on the quantitative analysis of the response of individual cells to controlled stimulations. The advent of microfluidics has revolutionized the methods to tailor the chemical environment of live cells, allowing stimulations to be applied with high spatiotemporal control and using minute amounts of reagents. It has been shown that Dictyostelium Discoideum cells (D.D.) can sense cAMP gradients on scales smaller than their size (a few tens of microns) and can adapt to very rapid concentration changes on sub second timescales. Classical methods to apply chemical stimulations, which are often based on the diffusion of solutes released by micropipettes, suffer from a poor spatial and temporal resolution and cannot discriminate the different timescales involved in the gradient sensing mechanism of D.D. Here we take advantage of a recently developed microfluidic toolbox based on microfluidic stickers made out of stiff polymers to stimulate adherent D.D. cells within microchannels. Microfluidic stickers allow for periodic chemical stimulation at the subcellular scale at frequencies up to 10Hz.We will present the dependence of the gradient sensing response as a function of both the temporal and spatial frequency. We will show how the microfluidic framework used in this study overcomes several experimental limitations and thus considerably extends previous investigations on the chemotaxis of D.D. by giving a new insight on previously proposed gradient sensing models.

Sensitivity to weak directional signals is a striking feature of chemotactic systems. In eukaryotic cells, it is often attributed to spatial amplification in the detection of the gradient of guidance cues due to an asymmetric distribution of signaling molecules of the signaling pathway. By combining single-quantum dot imaging with a guidance assay, we probed the dynamics of GABAA receptors (GABAARs) in nerve growth cones. In presence of a GABA gradient, we observed a lateral redistribution of the receptors towards the GABA source. This effect was both reversible and specific of GABA signals. Its functional implication was established by calcium imaging which showed that the redistribution was accompanied by an enhanced asymmetry of the calcium response. Furthermore, single quantum-dot tracking of GABAARs revealed a “conveyor-belt” type of motion in which receptors randomly alternated between periods of free diffusion and of microtubule-dependent directed movement.We therefore propose a model in which an asymmetric activation by the signaling gradient leads to oriented growth of the MTs which, in turn, contributes to an asymmetric distribution of the receptors and amplification in gradient sensing. This simple model for the formation of polarity at the cell membrane is supported by numerical simulations that describe with minimal hypothesis the results of our experiments. These simulations also provide predictions on the dependence of the formation of polarity as a function of gradient parameters. We will finally show our current effort to place neurons in microfluidic devices, to generate controlled gradients and to characterize the growth cone as a sensing, amplifying and filtering module.

During development of the nervous system, the tip of a growing axon, the growth cone (GC), must respond accurately to stimuli that direct its growth. This axonal navigation depends on extracellular concentration gradients of numerous guidance cues, including GABA. GCs can detect even weak directional signals, yet the mechanisms underlying this sensitivity remain unclear. Past studies in other eukaryotic chemotactic systems have pointed to the role of the spatial reorganization of the transduction pathway in their sensitive response. Here we have developed a single-molecule assay to observe individual GABA A receptors (GABA A Rs) in the plasma membrane of nerve GCs subjected to directional stimuli. We report that in the presence of an external GABA gradient GABA A Rs redistribute asymmetrically across the GC toward the gradient source. Single-particle tracking of GABA A Rs shows that the redistribution results from transient interactions between the receptors and the microtubules. Moreover, the relocalization is accompanied by an enhancement in the asymmetry of intracellular calcium concentration. Altogether, our results reveal a microtubule-dependent polarized reorganization of chemoreceptors at the cell surface and suggest that this polarization serves as an amplification step in GABA gradient sensing by nerve GCs.

El proceso de reconstrucción después del sismo que afectó al Perú el 15 de agosto de 2007 resulta siendo profundamente desigual. En efecto, a más de un año del desastre, muy pocas familias están en capacidad de reconstruir sus viviendas. Están excluidos de la reconstrucción los más pobres y sobre todo aquellos que no pudieron apoyarse en buenas redes sociales y de poder. Es lo que revela una encuesta realizada dirigida a 1 703 familias damnificadas de la provincia de Chincha. La encuesta muestra también que la vulnerabilidad de la población, ya elevada antes del sismo, se ha incrementado desde entonces, en razón del aumento de la precariedad de las familias, del incremento de la vulnerabilidad de las construcciones y de una cohesión social debilitada. Le processus de reconstruction ayant fait suite au séisme qui a affecté le Pérou le 15 août 2007 s’avère profondément inégalitaire. En effet, très peu de familles sont en mesure de reconstruire plus d’un an après la catastrophe. Les plus pauvres et, surtout, ceux qui n’ont pas été en mesure de s’appuyer sur les bons réseaux sociaux et de pouvoir, se voient exclus du processus de reconstruction. C’est ce que révèle une enquête réalisée auprès de 1 703 familles sinistrées de la province de Chincha. L’enquête montre également que la vulnérabilité de la population, déjà élevée avant le séisme, s’est accrue depuis, en raison du renforcement de la précarité des familles, de l’accroissement de la vulnérabilité du bâti et d’une cohésion sociale remise en cause. The rebuilding process following the seismic event which affected Peru on August 15, 2007 was deeply inegalitarian. Indeed, very few families were able to rebuild even more than one year after the disaster. The poorest, especially the ones who were not able to rely on the support of the social and power networks, were excluded from the rebuilding process. A survey was carried out with 1703 disaster victim families of the Chincha province and it shows that the population vulnerability, which was already high before the earthquake, increased because of the reinforcement of family precariousness, of the increase in vulnerability of constructions, and the fact that the social cohesion has been weakened.

International audience; We describe the first method to control, in a single microfluidic device, the generation, fusion, and mixing of pico- to nanoliter water-in-oil drops using a straightforward LED light stimulus. This is achieved by implementing a photosensitive surfactant in the water phases of a novel dual flow-focusing microfluidic configuration. UV illumination at 365 nm enables dynamic switch of the flow behavior between a stable dual jet regime (−UV) and a stable dual drop regime (+UV), thus allowing us to generate on-demand two distinct populations of water drops. These drops are fused and mixed downstream inside expansion chambers, offering both a dynamic control by light stimulation and a controllable degree of fusion and mixing by the positions of chambers. The mixing inside the fused drops is found to be much faster than diffusion due to the chaotic advection inside the moving drops.; Grâce à l’introduction d’un tensioactif photosensible dans les phases aqueuses d’un nouveau type de dispositif microfluidique à double focalisation de flux, nous décrivons pour la première fois le contrôle de la génération, de la fusion et du mélange de microgouttes aqueuses dispersées dans une phase d’huile, à l’aide d’un stimulus lumineux produit par une simple diode électroluminescente. Une illumination UV à 365 nm fait basculer réversiblement l’écoulement entre un régime à double jet (−UV) et un régime à double train de gouttes (+UV), nous permettant ainsi de générer à la demande, et de manière dynamique, deux populations de gouttes de compositions distinctes. Des chambres d’expansion permettent d’induire la fusion des gouttes générées par la lumière et de contrôler ainsi le mélange de leurs composants. Nous montrons que la position des chambres définit le degré de fusion et de mélange. Ce mélange s’opère de manière bien plus rapide que le temps caractéristique de diffusion des composants, grâce à l’advection chaotique créée au sein des gouttes en mouvement.