Laboratoire P.A.S.T.E.U.R.

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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.

 

Nanometric emulsions encapsulating solid particles as alternative carriers for intracellular delivery

In the current study we developed a multi-functional platform based on oil-in-water emulsions. These nano-vehicles (360 nm) are composed of an edible oil core stabilised by a biocompatible surfactant and encapsulate hydrophobic-functionalised silica nanoparticles (60 nm). The concept is depicted in Figure 1. The silica nanoparticles were rendered fluorescent by covalent grafting to use fluorescence microscopy to track the particles during cell studies. After characterisation, the particles were incubated with model epithelial cells HeLa to determine the effect of solid particles encapsulation within an oil droplet on their interaction with the cells, their internalisation pathway and subsequent intracellular fate as compared to free solid nanoparticles.

Light-Driven Transport of a Liquid Marble with and against Surface Flows

Angew. Chem. Int. Ed. 2016, 55, 11183 –11187

 

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”.

 

Mechanism and analyses for extracting photosynthetic electrons using exogenous quinones – what makes a good extraction pathway?

Photochem. Photobiol. Sci., 2016,15, 969-979

 

Plants or algae take many bene!ts from oxygenic photosynthesis by converting solar energy into chemical energy through the synthesis of carbohydrates from carbon dioxide and water. However, the overall yield of this process is rather low (about 4% of the total energy available from sunlight is converted into chemical energy). This is the principal reason why recently many studies have been devoted to extraction of photosynthetic electrons in order to produce a sustainable electric current. Practically, the electron transfer occurs between the photosynthetic organism and an electrode and can be assisted by an exogenous mediator, mainly a quinone. In this regard, we recently reported on a method involving "uorescence measurements to estimate the ability of di#erent quinones to extract photosynthetic electrons from a mutant of Chlamydomonas reinhardtii. In the present work, we used the same kind of methodology to establish a zone diagram for predicting the most suitable experimental conditions to extract photoelectrons from intact algae (quinone concentration and light intensity) as a function of the purpose of the study. This will provide further insights into the extraction mechanism of photosynthetic electrons using exogenous quinones. Indeed "uorescence measurements allowed us to model the capacity of photosynthetic algae to donate electrons to an exogenous quinone by considering a numerical parameter called “open center ratio” which is related to the Photosystem II acceptor redox state. Then, using it as a proxy for investigating the extraction of photosynthetic electrons by means of an exogenous quinone, 2,6-DCBQ, we suggested an extraction mechanism that was globally found consistent with the experimentally extracted parameters.

Temperature-Switchable Control of Ligand Display on Adlayers of Mixed Poly(lysine)‑g‑(PEO) and Poly(lysine)‑g‑(ligand-modified poly‑N‑isopropylacrylamide)

Biomacromolecules2016 May 9;17(5):1727-36

 

Adlayers of poly(lysine)-g -PEG comblike copolymer are extensively used to prepare cell-repellant and proteinrepellent surfaces by a straightforward coulomb-driven adsorption that is compatible with diverse substrates (glass, Petri dish, etc.). To endow surfaces with functional properties, namely, controlled ligand-protein binding, comblike poly(lysine) derivatives were used to deposit temperature-responsive poly(NIPAM) macrografts mixed with PEG ones on glass surfaces. Simple surface immersion in mixed solutions of biotin-modifi ed poly(lysine)-g -poly(N -isopropylacrylamide) and poly(lysine)-g -poly(ethylene oxide) yielded robust adlayers whose composition refl ected the ratio between the two polymers in solution. We show by fluorescence imaging, and comparison with repellent 100% PEGylated patterns, that specifi c binding of model avidin/particle conjugates (diameters of ca. 10 or 200 nm) was controlled by temperature switch. The biotin ligand was displayed and accessible at low T , or hidden at T  > LCST. Topography and mechanical mapping measurements by AFM confi rmed the swelling/collapse status of PNIPAM macrografts in the adlayer at low/high T , respectively. Temperature-responsive comblike PLL derivative that can spontaneously cover anionic interfaces is a promising platform enabling good control on the deposition and accessibility of biofunctional groups on various solid surfaces