Microcontact printing process for the patterned growth of individual CNTs

We report an original approach to pattern a substrate with isolated carbon nanotubes. Through the improvement of the microcontact printing technique by the use of a new composite stamp, we were able to produce on flat substrates micrometric features of a catalyst suitable for the localised growth of single-walled carbon nanotubes by catalytic chemical vapour deposition. This catalyst material is for the first time prepared via an original sol–gel process. The growth of straight carbon nanotubes between the patterns was observed and a method to promote the controlled growth of such isolated nanoobjects is thus conceivable

Collective beating of artificial microcilia

We combine technical, experimental and theoretical efforts to investigate the collective dynamics of artificial microcilia in a viscous fluid. We take advantage of soft-lithography and colloidal self-assembly to devise microcapets made of hundreds of slender magnetic rods. This novel experimental setup is used to investigate the dynamics of extended cilia arrays driven by a precessing magnetic field. Whereas the dynamics of an isolated cilium is a rigid body rotation, collective beating results in a symmetry breaking of the precession patterns. The trajectories of the cilia are anisotropic and experience a significant structural evolution as the actuation frequency increases. We present a minimal model to account for our experimental findings and demonstrate how the global geometry of the array imposes the shape of the trajectories via long range hydrodynamic interactions.Comment: 5 pages, 3 figure

Stress Clamp Experiments on Multicellular Tumor Spheroids

The precise role of the microenvironment on tumor growth is poorly understood. Whereas the tumor is in constant competition with the surrounding tissue, little is known about the mechanics of this interaction. Using a novel experimental procedure, we study quantitatively the effect of an applied mechanical stress on the long-term growth of a spheroid cell aggregate. We observe that a stress of 10 kPa is sufficient to drastically reduce growth by inhibition of cell proliferation mainly in the core of the spheroid. We compare the results to a simple numerical model developed to describe the role of mechanics in cancer progression.Comment: 5 pages, 4 figure

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

Microenvironnements pour l’analyse biologique et l’ingéniérie des tissus

National audienceAu sein des tissus vivants, les cellules forment une communauté organisée et en interaction dans d’une matrice extra cellulaire. De ce microenvironnement cellulaire, naissent les mécanismes responsables de l’homéostasie ou de la dégénérescence des tissus qui sont étroitement liés à la topologie ainsi qu’à la distribution spatiale des propriétés physico-chimiques et biologiques. Ainsi, la fabrication de modèles mimétiques permettant de reproduire, en trois dimensions, les paramètres physiques et chimiques essentiels du microenvironnement, est devenu un enjeu majeur en biologie et en médecine. Dans cet objectif, les technologies microfluidiques et de bioimpression apparaissent comme des outils particulièrement performants pour créer des modèles de microenvironnements propices à la manipulation de liquides biologiques, à leur traitement à des fins d’analyse ou d’étude de la prolifération cellulaire. Cette soutenance sera dédiée, dans un premier temps, à une présentation des projets de recherches menés au sein de l’institut Curie puis au sein du LAAS CNRS autour du développement de de concepts microfluidiques pour la réalisation de dispositifs miniaturisés d’analyse (pré-concentration, capture et analyse de biomarqueurs et de cellules) ou de diagnostic cellulaire (capture de cellules tumorales circulantes, analyse génétique). Dans un deuxième temps seront présentées les évolutions de ces activités de recherche vers le développement de modèles standardisés de microenvironnements cellulaires sur la base de technologies d’impression 3D et de bioimpression

Dispositifs ultra-sensibles pour le nano-adressage electrique. Application a la detection de biomolecules

" Because technology provides the tools and biology the problems, the two should enjoy a happy marriage ! " 1. This sentence perfectly summarizes the spirit of the project underling this thesis. Indeed, the so-called fiNanobiotechnologies, that couple Micro and Nanotechnologies with biotechnologies, is an emerging domain, potentially vector of many applications as for example in the field of biodetection. The main objective of this work is dedicated to the development of new strategies for addressing biomolecules at the nanometer scale for the development of biodetection applications. The first aspect of this work is technological. Using a planar process on silicon involving high-resolution electron beam lithography and lift-off, we have demonstrated the possible fabrication of nanoelectrodes based devices presenting gaps with controlled dimensions ranging from 100nm down to 15nm. An alternative method to electron beam lithography called NanoImprint Lithography is also presented as a possible way to replicate these devices. The second part is dedicated to the implementation of a nanosystem capable to detect metallic nanoparticles using interdigitated nanoelectrodes array based device. Before applying this procedure to a biodetection application, we have studied the electrical response of these devices versus the immobilization of gold nanoparticles on their active surface. The results indicate that the response is highly sensitive and that the detection of a single nanoparticle is possible using a direct conductance measurement. Finally, these devices were used to achieve the electrical detection of biomolecules labeled with gold nanoparticles. This approach was successfully applied to the electrical detection of antigene/antibody interactions. Combining this method with a conventional detection scheme based on the interaction between a target and a probe molecules, we have demonstrated that the selectivity of the biomolecular recognition can be revealed by the im mobilization of nanoparticles on the surface and finally translated into a drastic modification of the electrical transport through the device. The integration capacities and the compatibility of this detection schema with microfluidics open very interesting perspectives for the development of high sensitive integrated biochips. 1 S. Fields, Proc. Natl. Acad. Sci. USA, vol 98, pp 10051-10054 (2001)" Because technology provides the tools and biology the problems, the two should enjoy a happy marriage ! "1 . Cette phrase resume parfaitement l'esprit du projet qui a motive ces travaux de these. En effet, le couplage des biotechnologies et des micro et nano technologies, resume sous le vocable est une activite en plein essor qui laisse presager de nombreuses applications en particulier dans le domaine de la biodetection. Lobjectif principal de ces travaux est dedie au developpement de strategies d'adressage de biomolecules a l'echelle nanometrique pour des applications de biodetection. Le premier aspect de ce travail est d'ordre technologique. Il concerne la fabrication de dispositifs d'adressage bases sur des reseaux de nanoelectrodes planaires. En utilisant un procede reposant sur lutilisation de la lithographie electronique haute resolution sur un microscope TEM/STEM, nous avons pu demontrer la fabrication de dispositifs a base de nanoelectrodes presentant des espaces inter-electrodes controlables entre 100 et 15nm. Une technique de lithographie alternative, la Nano-Impression est egalement presentee comme une solution possible a la replication de nanodispositifs fabriques par lithographie electronique. La deuxieme partie des travaux est dediee a la mise en place dun schema de detection de nanoparticules que nous avons developpe autour de dispositifs bases sur des reseaux delectrodes inter-digitees. Avant de nous interesser a l'utilisation de ces dispositifs pour une application biologique, nous avons etudie leur reponse electrique vis-a-vis de l'absorption de nanoparticules d'Or par interaction electrostatique. Les premiers resultats obtenus montrent que le schema de detection permet d'atteindre un niveau de sensibilite ultime au travers d'une mesure directe de la conductance des dispositifs. Certaines experiences montrent en effet la possibilite de mesurer electriquement l'adsorption d'une seule nanoparticule. Enfin, la derniere partie de ces travaux est dediee a l'adaptation de ce protocole pour la detection de biomolecules fonctionnalisees par des nanoparticules d'Or. Pour cela, nous avons employe une approche simple basee sur un systeme de reconnaissance entre une molecule cible et une molecule sonde. Ce schema a ete applique a la detection d'interaction antigene/anticorps et nous a permis de transcrire la selectivite de la reconnaissance entre les anticorps dans le depot des nanoparticules qui se traduit par une modification importante de la conductance du dispositif. Les possibilites d'integration ainsi que la compatibilite des dispositifs avec des systemes de microfluidique rendent ce schema de detection particulierement adapte pour le developpement d'un systeme integre de biodetection a tres haute sensibilite. 1 S. Fields, Proc. Natl. Acad. Sci. USA, vol 98, pp 10051-10054 (2001

Dispositifs ultra-sensibles pour le nano-adressage électrique (application à la détection de biomolécules)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

In vitro models of intestinal epithelium: towards bioengineered systems.

International audienceThe intestinal epithelium, the fastest renewing tissue in human, is a complex tissue hosting multiple cell types with a dynamic and multiparametric microenvironment, making it particularly challenging to recreate in vitro. Convergence of recent advances in cellular biology and microfabrication technologies have led to the development of various bioengineered systems to model and study the intestinal epithelium. Theses microfabricated in vitro models may constitute an alternative to current approaches for studying the fundamental mechanisms governing intestinal homeostasis and pathologies, as well as for in vitro drug screening and testing. Herein, we review the recent advances in bioengineered in vitro intestinal models