UMR 8640 : Microfluidics

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Magnetic actuation of discrete liquid entities with a deformable paramagnetic liquid substrate

Angewandte Chemie (2017) 


Because miniaturization is accompanied by an increase in the surface-over-volume ratio, most strategies for controlled manipulation of small-sized drops on substrates have relied on exploiting interfacial energy gradients, making it possible to actuate drops with various stimuli, including electrical or optical ones, but requiring adequate stimulus-responsive systems. In contrast, 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 or oil, unless magnetosensitive particles are added. Here, we describe a new way to magnetically control the motion of discrete liquid entities, in an additive-free and surface tension-independent manner. 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. We demonstrate that, in our configuration, it is the substrate deformation that mainly dictates the behaviour of the floating liquid entity. We show that a broad variety of liquids, including diamagnetic (water, oil) and nonmagnetic ones can be efficiently transported using the moderate magnetic field (≈ 50 mT) produced by a cost-effective, cmsized permanent magnet. Complex trajectories can be achieved in a reliable manner and multiplexing potential is demonstrated through on-demand drop fusion. Our paramagnetofluidic method advantageously works without any complex equipment nor electric power, in phase with the necessary development of robust and lowcost analytical and diagnostic fluidic devices.

Human Pluripotent Stem Cell-Derived Cardiac Tissue-like Constructs for Repairing the Infarcted Myocardium

Stem Cell Reports, 2017, 9, 1546–1559


High-purity cardiomyocytes (CMs) derived from human induced pluripotent stem cells (hiPSCs) are promising for drug development and myocardial regeneration. However, most hiPSC-derived CMs morphologically and functionally resemble immature rather than adult CMs, which could hamper their application. Here, we obtained high-quality cardiac tissue-like constructs (CTLCs) by cultivating hiPSC-CMs on low-thickness aligned nanofibers made of biodegradable poly(D,L-lactic-co-glycolic acid) polymer. We show that multilayered and elongated CMs could be organized at high density along aligned nanofibers in a simple one-step seeding process, resulting in upregulated cardiac biomarkers and enhanced cardiac functions. When used for drug assessment, CTLCs were much more robust than the 2D conventional control.We also demonstrated the potential of CTLCs for modeling engraftments in vitro and treating myocardial infarction in vivo. Thus, we established a handy framework for cardiac tissue engineering, which holds high potential for pharmaceutical and clinical applications.


Intramolecularly Protein-Crosslinked DNA Gels: New Biohybrid Nanomaterials with Controllable Size and Catalytic Activity

Small 2017, 1700706


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 submicrometer-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).

Protein Adsorption and Reorganization on Nanoparticles Probed by the Coffee- Ring Effect: Application to Single Point Mutation Detection

J. Am. Chem. Soc 2016, 138, 11623–11632


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 diff erent 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 fi ndings 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. 


Induction and differentiation of human induced pluripotent stem cells into functional cardiomyocytes on a compartmented monolayer of gelatin nanofibers

Nanoscale, 2016, 8, 14530


Extensive efforts have been devoted to develop new substrates for culture and differentiation of human induced pluripotent stem cells (hiPSCs) toward cardiac cell-based assays. A more exciting prospect is the construction of cardiac tissue for robust drug screening and cardiac tissue repairing. Here, we developed a patch method by electrospinning and crosslinking of monolayer gelatin nanofibers on a honeycomb frame made of poly(ethylene glycol) diacrylate (PEGDA). The monolayer of the nanofibrous structure can support cells with minimal exogenous contact and a maximal efficiency of cell–medium exchange whereas a single hiPSC colony can be uniformly formed in each of the honeycomb compartments. By modulating the treatment time of the ROCK inhibitor Y-27632, the shape of the hiPSC colony could be controlled from a flat layer to a hemisphere. Afterwards, the induction and differentiation of hiPSCs were achieved on the same patch, leading to a uniform cardiac layer with homogeneous contraction. This cardiac layer could then be used for extracellular recording with a commercial multi-electrode array, showing representative field potential waveforms of matured cardiac tissues with appropriate drug responses.