Regular poly(para-phenylene) films bound to gold surfaces through the electrochemical reduction of diazonium salts followed by electropolymerization in an ionic liquid

International audienceBy combining the electroreduction of diazonium salts and the electropolymerization of conducting polymers in an ionic liquid, the electrografting of a regular poly(para-phenylene) film on a gold substrate is achieved, leading to the strong and robust anchoring of the PPP polymers on the substrate (Au-PPP hybrid). A thin layer covalently bound to the substrate is first prepared by the reduction of benzenediazonium salt (BD), then, on top of this layer, a thicker layer of poly(para-phenylene) (PPP) is easily grown by the electrochemical oxidation of biphenyl in the [BMIm][PF6] ionic liquid. The resulting material is thoroughly characterized by IR, ToF-SIMS and fluorescence spectroscopies. The analyses show the formation of well regular PPP layers that are wired to the substrate. The key role of the [BMIm][PF6] ionic liquid in the structuration of the polymer is emphasized

Mathematical modelling of oxygen transport in a muscle-on-chip device

Muscle-on-chip devices aim to recapitulate the physiological characteristics of in vivo muscle tissue and so maintaining levels of oxygen transported to cells is essential for cell survival and for providing the normoxic conditions experienced in vivo. We use finite-element method numerical modelling to describe oxygen transport and reaction in a proposed three-dimensional muscle-on-chip bioreactor with embedded channels for muscle cells and growth medium. We determine the feasibility of ensuring adequate oxygen for muscle cell survival in a device sealed from external oxygen sources and perfused via medium channels. We investigate the effects of varying elements of the bioreactor design on oxygen transport to optimize muscle tissue yield and maintain normoxic conditions. Successful co-culturing of muscle cells with motor neurons can boost muscle tissue function and so we estimate the maximum density of seeded neurons supported by oxygen concentrations within the bioreactor. We show that an enclosed bioreactor can provide sufficient oxygen for muscle cell survival and growth. We define a more efficient arrangement of muscle and perfusion chambers that can sustain a predicted 50% increase in maximum muscle volume per perfusion vessel. A study of simulated bioreactors provides functions for predicting bioreactor designs with normoxic conditions for any size of perfusion vessel, muscle chamber and distance between chambers

In-capillary immuno-preconcentration with circulating bio-functionalized magnetic beads for capillary electrophoresis

International audienceThis study reports on the conception of magneto-Capillary Electrophoresis (magneto-CE), an approach integrating immuno-capture on circulating bio-functionalized magnetic beads into a unique capillary for preconcentration and electrokinetic separation. This hybrid mode is an evolution of in-capillary magnetic bead-based operation from static cluster format to dynamic configuration where beads are allowed to controllably circulate inside a CE capillary for interaction improvement. To implement the magneto-CE operation, a purpose-made instrument was constructed, allowing visual observation of the movement of the magnetic beads. We applied a new methodological strategy for determination of the amyloid β peptide (Aβ 1–42), which is as an established biomarker for molecular diagnosis of Alzheimer's disease (AD). The methodology is based on magneto-immuno-capture of fluorescently labeled Aβ 1–42 followed by a chemical elution with a basic solution prior to CE separation with laser induced fluorescent (LIF) detection. The superiority of this dynamic configuration of magneto-CE was demonstrated for this target analyte, with sample pretreatment and separation being performed in-capillary without any delay in between and without any waste of pretreated sample, which otherwise would not be the case with offline/batch-wise operation

Combining Microfluidics, Optogenetics and Calcium Imaging to Study Neuronal Communication In Vitro

International audienceIn this paper we report the combination of microfluidics, optogenetics and calcium imaging as a cheap and convenient platform to study synaptic communication between neuronal populations in vitro. We first show that Calcium Orange indicator is compatible in vitro with a commonly used Channelrhodopsine-2 (ChR2) variant, as standard calcium imaging conditions did not alter significantly the activity of transduced cultures of rodent primary neurons. A fast, robust and scalable process for micro-chip fabrication was developed in parallel to build micro-compartmented cultures. Coupling optical fibers to each micro-compartment allowed for the independent control of ChR2 activation in the different populations without crosstalk. By analyzing the post-stimuli activity across the different populations, we finally show how this platform can be used to evaluate quantitatively the effective connectivity between connected neuronal populations

Magnetic Core Shell Nanoparticles Trapping in a Microdevice Generating High Magnetic Gradient

Magnetic core shell nanoparticles (MCSNPs) 30 nm diameter with a magnetic weight of 10% are usually much too small to be trapped in microfluidic systems using classical external magnets. Here, a simple microchip for efficient MCSNPs trapping and release is presented. It comprises a bed of micrometric iron beads (6–8 mm diameter) packed in a microchannel against a physical restriction and presenting a low dead volume of 0.8 nL. These beads of high magnetic permeability are used to focus magnetic field lines from an external permanent magnet and generate local high magnetic gradients. The nanoparticles magnetic trap has been characterised both by numerical simulations and fluorescent MCSNPs imaging. Numerical simulations have been performed to map both the magnetic flux density and the magnetic force, and showed that MCSNPs are preferentially trapped at the iron bead magnetic poles where the magnetic force is increased by 3 orders of magnitude. The trapping efficiency was experimentally determined using fluorescent MCSNPs for different flow rates, different iron beads and permanent magnet positions. At a flow rate of 100 mL h1, the nanoparticles trapping/release can be achieved within 20 s with a preconcentration factor of 4000

L' électrophorèse capillaire en milieu non aqueux (contribution à la compréhension des phénomènes physico-chimiques impliqués et applications)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Design of experiments as tools to tailor impregnated polymers specific for radionuclides separation in microsystems

An experimental design is described for optimization of the microscopic morphology of a methacrylate monolith that was elaborated for chromatographic separation of radionuclides in nitric acid media. This paper presents a systematic study of the synthesis of the polymeric porous monolith poly(ethylene glycol dimethacrylate-co-allyl methacrylate) used as solid-phase support and a post-functionalization of the monolith in microsystem with tributyl phosphate extractant. Polymerization time and chemical composition of the polymerizable mixture that comprises water, 1,4-butanediol, 1-propanol, monomers were chosen as the most relevant experimental factors of the photochemical process. Using the globules area as a significant response of an experimental design, the monolith morphology can be predicted. A new versatile and robust impregnation process was developed in microsystem. The designed micro chromatographic system showed a good resistance in concentrated nitric acid and a great loading capacity compared to commercially available solution (150 mg U versus 75 mgU/g resin)

Influence of electrolyte nature on the separation selectivity of amphetamines in nonaqueous capillary electrophoresis: Protonation degree versus ion pairing effects

The simultaneous analysis of Ecstasy and its derivatives in an acetonitrile-methanol (80:20 v/v) mixture was previously shown to be strongly dependent on the nature of the electrolyte (acetate versus formate). To elucidate the phenomena involved, systematic experiments were conducted in this solvent medium. Conductivity measurements allowed to evaluate the ion-pairing rate in the background electrolyte (BGE) and thereby distinguish between electrolyte concentration and ionic strength. The influence of electrolyte concentration on analyte effective mobilities micro(eff)) was studied by capillary electrophoresis (CE). As micro(eff) extrapolated to infinite dilution proved to be independent of the nature of the electrolyte, selectivity changes could not be attributed to a modification in the protonation degree of amphetamines. Experimental mobility data were then confronted to existing theoretical mobility models to discriminate between ion pairing or simple ionic strength effect. Ion-pair formation in a BGE containing acetate was highlighted with an ion-pairing model and ion-pair formation constants between each amphetamine and acetate ion were calculated