Peer-reviewed Publications |
Aldeek, F., Mustin, C., Balan, L., Roques-Carmes, T., Fontaine-Aupart, M. - P., & Schneider, R. (2011). Surface-engineered quantum dots for the labeling of hydrophobic microdomains in bacterial biofilms. BIOMATERIALS, 32(23), 5459–5470.
Résumé: Quantum dots (QDs) nanoprobes are emerging as alternatives to small-molecule fluorescent probes in biomedical technology. This paper reports an efficient and rapid method of producing highly dispersed and stable CdSe-core QDs with a hydrophobic gradient. Amphiphilic core/shell CdSe/ZnS QDs were prepared by ligand exchange at the surface of lipophilic CdSe/ZnS QDs using the dihydrolipoic acid (DHLA) dithiol ligand linked to Leucine or Phenylalanine aminoacids. Contact angle relaxations on a hydrophobic surface and surface tension measurements indicated that aqueous dispersions of CdSe/ZnS@DHLA-Leu or CdSe/ZnS@DHLA-Phe QDs exhibit increased hydrophobicity compared to CdSe-core QDs capped by the hydrophilic 3-mercaptopropionic acid (MPA) ligand. We found that the surface functional groups and the ligand density at the periphery of these QDs significantly dictated their interactions with a complex biological matrix called biofilm. Using fluorescence confocal microscopy and an autocorrelation function (semi-variogram), we demonstrated that MPA-capped QDs were homogeneously associated to the biopolymers, while amphiphilic CdSe/ZnS@DHLA-Leu or CdSe/ZnS@DHLA-Phe QDs were specifically confined allowing identification of hydrophobic microdomains of the biofilms. Results obtained clearly point out that the final destination of QDs in biofilms can properly be controlled by an appropriate design of surface ligands. (C) 2011 Elsevier Ltd. All rights reserved.
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Aubry, G., Kou, Q., Soto-Velasco, J., Wang, C., Meance, S., He, J. J., & Haghiri-Gosnet, A. M. (2011). A multicolor microfluidic droplet dye laser with single mode emission. APPLIED PHYSICS LETTERS, 98(11), 111111.
Résumé: A digital microfluidic dye laser that integrates a Fabry-Perot cavity with two fiber-based mirrors is shown to exhibit a single mode emission. In addition, fast switching is achieved via the alternation of droplet streams that contain two different dyes. Single-longitudinal-mode emission is observed for each dye wavelength (at 565 and 586 nm) with a linewidth narrower than 0.12 nm. This system appears thus well suited for on-chip spectroscopy and flow cytometry. (C) 2011 American Institute of Physics. [doi:10.1063/1.3565242]
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Aubry, G., Wang, C., Soto-Velasco, J., Meance, S., Haghiri-Gosnet, A. - M., & Kou, Q. (2011). On-chip production of liquid optical microcavities. MICROELECTRONIC ENGINEERING, 88(8), 2618–2621.
Résumé: Microfluidic production of droplets acting as optical resonators has been investigated for different liquid materials and cross-junction geometries. Liquid couples are selected to meet the requirements to refractive indexes. The generation of unconfined droplets is studied by monitoring the liquid flow rates and by changing the channel geometry. Such optical resonators used passively or actively can be of great interest as on-chip laser sources or biosensors. (C) 2011 Elsevier B.V. All rights reserved.
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Barroca, T., Balaa, K., Delahaye, J., Leveque-Fort, S., & Fort, E. (2011). Full-field supercritical angle fluorescence microscopy for live cell imaging. OPTICS LETTERS, 36(16), 3051–3053.
Résumé: We introduce a full-field fluorescence imaging technique with axial confinement of about 100nm at the sample/substrate interface. Contrary to standard surface imaging techniques, this confinement is obtained through emission filtering. This technique is based on supercritical emission selectivity. It can be implemented on any epifluorescence microscope with a commercial high numerical aperture objective and offers a real-time surface imaging capability. This technique is of particular interest for live cell membrane and adhesion studies. Using human embryonic kidney cells, we show that one can observe simultaneously the surface and in-depth cell phenomena. (C) 2011 Optical Society of America
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Bulard, E., Guo, Z., Zheng, W., Dubost, H., Fontaine-Aupart, M. - P., Bellon-Fontaine, M. - N., Herry, J. - M., Briandet, R., & Bourguignon, B. (2011). Non-Invasive Vibrational SFG Spectroscopy Reveals That Bacterial Adhesion Can Alter the Conformation of Grafted “Brush” Chains on SAM. Langmuir, 27(8), 4928–4935.
Résumé: Understanding bacterial adhesion on a surface is a crucial step to design new materials with improved properties or to control biofilm formation and eradication. Sum Frequency Generation (SFG) vibrational spectroscopy has been employed to study in situ the conformational response of a self-assembled monolayer (SAM) of octadecanethiol (ODT) on a gold film to the adhesion of hydrophilic and hydrophobic ovococcoid model bacteria. The present work highlights vibrational SFG spectroscopy as a powerful and unique non-invasive biophysical technique to probe and control bacteria interaction with ordered surfaces. Indeed, the SFG vibrational spectral changes reveal different ODT SAM conformations in air and upon exposure to aqueous solution or bacterial adhesion. Furthermore, this effect depends on the bacterial cell surface properties. The SFG spectral modeling demonstrates that hydrophobic bacteria flatten the ODT SAM alkyl chain terminal part, whereas the hydrophilic ones raise this ODT SAM terminal part. Microorganism-induced alteration of grafted chains can thus affect the desired interfacial functionality, a result that should be considered for the design of new reactive materials.
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Habimana, O., Steenkeste, K., Fontaine-Aupart, M. - P., Bellon-Fontaine, M. - N., Kulakauskas, S., & Briandet, R. (2011). Diffusion of Nanoparticles in Biofilms Is Altered by Bacterial Cell Wall Hydrophobicity. APPLIED AND ENVIRONMENTAL MICROBIOLOGY, 77(1), 367–368.
Résumé: Diffusion of entities inside biofilm triggers most mechanisms involved in biofilm-specific phenotypes. Using genetically engineered hydrophilic and hydrophobic cells of Lactococcus lactis yielding similar biofilm architectures, we demonstrated by fluorescence correlation spectroscopy that bacterial surface properties affect diffusion of nanoparticles through the biofilm matrix.
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Marquer, C., Devauges, V., Cossec, J. - C., Liot, G., Lecart, S., Saudou, F., Duyckaerts, C., Leveque-Fort, S., & Potier, M. - C. (2011). Local cholesterol increase triggers amyloid precursor protein-Bace1 clustering in lipid rafts and rapid endocytosis. FASEB JOURNAL, 25(4), 1295–1305.
Résumé: Amyloid peptide (A beta) is generated by sequential cleavage of the amyloid precursor protein (APP) by beta-secretase (Bace1) and gamma-secretase. A beta production increases after plasma membrane cholesterol loading through unknown mechanisms. To determine how APP-Bace1 proximity affects this phenomenon, we developed a fluorescence lifetime imaging microscopy-Forster resonance energy transfer (FLIM-FRET) technique for visualization of these molecules either by epifluorescence or at the plasma membrane only using total internal reflection fluorescence. Further, we used fluorescence correlation spectroscopy to determine the lipid rafts partition of APP-yellow fluorescent protein (YFP) and Bace1-green fluorescent protein (GFP) molecules at the plasma membrane of neurons. We show that less than 10 min after cholesterol exposure, Bace1-GFP/APP-mCherry proximity increases selectively at the membrane and APP relocalizes to raft domains, preceded by rapid endocytosis. After longer cholesterol exposures, APP and Bace1 are found in proximity intracellularly. We demonstrate that cholesterol loading does not increase A beta production by having a direct impact on Bace1 catalytic activity but rather by altering the accessibility of Bace1 to its substrate, APP. This change in accessibility is mediated by clustering in lipid rafts, followed by rapid endocytosis.-Marquer, C., Devauges, V., Cossec, J.-C., Liot, G., Lecart, S., Saudou, F., Duyckaerts, C., Leveque-Fort, S., Potier, M.-C. Local cholesterol increase triggers amyloid precursor protein-Bace1 clustering in lipid rafts and rapid endocytosis. FASEB J. 25, 1295-1305 (2011). www.fasebj.org
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Meance, S., Papin, K., Gamby, J., Aubry, G., Kou, Q., & Haghiri-Gosnet, A. - M. (2011). An integrated on chip organic optical source based on electrochemiluminescence. MICROELECTRONIC ENGINEERING, 88(8), 1798–1800.
Résumé: We report here on an original “glass-PDMS-glass” electrochemiluminescence optofluidic device that integrates 32 electrodes on a large surface. This organic electrically powered light source has been integrated on chip using an alternative process based on a photopatternable silicone resist. Under a continuous flow rate, this device allows electrogenerated chemiluminescence for several minutes which would be very useful for future μTAS systems. (C) 2011 Elsevier B.V. All rights reserved.
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Ros, D., Cassou, K., Cros, B., Daboussi, S., Demailly, J., Guilbaud, A., Kazamias, S., Lagron, J. - C., Maynard, G., Neveu, O., Pittman, M., Zielbauer, B., Zimmer, D., Kuhl, T., Lacombe, S., Porcel, E., du Penhoat, M. - A., Zeitoun, P., & Mourou, G. (2011). LASERIX: An open facility for developments of EUV and soft X-ray lasers and applications-Developments of XUV sources using high power laser facilities: ILE, ELI. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 653(1), 76–79.
Résumé: LASERIX is a high-power laser facility leading to High-repetition-rate XUV laser pumped by Titanium:Sapphire laser. The aim of this laser facility is to offer Soft XRLs in the 30-7 nm range and auxiliary IR beam, which could also be used to produce synchronized XUV sources. In this contribution, the main results concerning both the development of XUV sources and their use for applications (irradiation of DNA samples) are presented, as well the present status and some perspectives for LASERIX. (C) 2011 Elsevier B.V. All rights reserved.
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Sarsa, A., & Le Sech, C. (2011). Variational Monte Carlo Method with Dirichlet Boundary Conditions: Application to the Study of Confined Systems by Impenetrable Surfaces with Different Symmetries. JOURNAL OF CHEMICAL THEORY AND COMPUTATION, 7(9), 2786–2794.
Résumé: Variational Monte Carlo method is a powerful tool to determine approximate wave functions of atoms, molecules, and solids up to relatively large systems. In the present work, we extend the variational Monte Carlo approach to study confined systems. Important properties of the atoms, such as the spatial distribution of the electronic charge, the energy levels, or the filling of electronic shells, are modified under confinement. An expression of the energy very similar to the estimator used for free systems is derived. This opens the possibility to study confined systems with little changes in the solution of the corresponding free systems. This is illustrated by the study of helium atom in its ground state (1)S and the first (3)S excited state confined by spherical, cylindrical, and plane impenetrable surfaces. The average interelectronic distances are also calculated. They decrease in general when the confinement is stronger; however, it is seen that they present a minimum for excited states under confinement by open surfaces (cylindrical, planes) around the radii values corresponding to ionization. The ground (2)S and the first (2)P and (2)D excited states of the lithium atom are calculated under spherical constraints for different confinement radii. A crossing between the (2)S and (2)P states is observed around r(c) = 3 atomic units, illustrating the modification of the atomic energy level under confinement. Finally the carbon atom is studied in the spherical symmetry by using both variational and diffusion Monte Carlo methods. It is shown that the hybridized state sp(3) becomes lower in energy than the ground state (3)P due to a modification and a mixing of the atomic orbitals s, p under strong confinement. This result suggests a model, at least of pedagogical interest, to interpret the basic properties of carbon atom in chemistry.
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Actes de Conférences |
Bridier, A., Tischenko, E., Dubois-Brissonnet, F., Herry, J. - M., Thomas, V., Daddi-Oubekka, S., Waharte, F., Steenkeste, K., Fontaine-Aupart, M. - P., & Briandet, R. (2011). Deciphering Biofilm Structure and Reactivity by Multiscale Time-Resolved Fluorescence Analysis. In BACTERIAL ADHESION: CHEMISTRY (Vol. 715, pp. 333–349).
Résumé: In natural, industrial and medical environments, microorganisms mainly live as structured and organised matrix-encased communities known as biofilms. In these communities, microorganisms demonstrate coordinated behaviour and are able to perform specific functions such as dramatic resistance to antimicrobials, which potentially lead to major public health and industrial problems. It is now recognised that the appearance of such specific biofilm functions is intimately related to the three-dimensional organisation of the biological edifice, and results from multifactorial processes. During the last decade, the emergence of innovative optical microscopy techniques such as confocal laser scanning microscopy in combination with fluorescent labelling has radically transformed imaging in biofilm research, giving the possibility to investigate non-invasively the dynamic mechanisms of formation and reactivity of these biostructures. In this chapter, we discuss the contribution of fluorescence analysis and imaging to the study at different timescales of various processes: biofilm development (hours to days), antimicrobial reactivity within the three-dimensional structure (minutes to hours) or molecular diffusion/reaction phenomena (pico- to milliseconds).
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Bulard, E., Dubost, H., Fontaine-Aupart, M. - P., Zheng, W., Herry, J. - M., Bellon-Fontaine, M. - N., Briandet, R., & Bourguignon, B. (2011). Non invasive SFG spectroscopy: a tool to reveal the conformational change of grafted chains due to bacterial adhesion. In CLINICAL AND BIOMEDICAL SPECTROSCOPY AND IMAGING II (Vol. 8087).
Résumé: In many fields such as biomedical or food industry, surface colonization by micro-organisms leads to biofilms formation that are tridimentional biostructures highly resistant to the action of antimicrobials, by mechanisms still unclear. In order to deepen our understanding of the initial interaction of bacteria cells with a solid surface, we analyze by in situ vibrational Sum Frequency Generation (SFG) spectroscopy the effect of the adhesion of hydrophilic Lactoccocus lactis bacteria and its hydrophobic mutants in distilled water on a self-assembled monolayer (SAM) of octadecanethiol (ODT) on a gold film. When a homogeneous bacterial monolayer is deposited on this ordered surface, SFG spectrum of the ODT SAM shows significant intensity changes from that in air or in water. Its modelling as a function of conformation allows to distinguish optical effects due to the water solution surrounding bacteria from conformational changes of the ODT SAM due to the presence of the bacteria cells. Futhermore, bacterial adhesion induces different measurable effects on the ODT SAM conformation, depending on the hydrophobic / hydrophilic character of the bacterial surface. Such a result deserves to be taken into account for the design of new materials with improved properties or to control biofilm formation.
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Constans, J. M., Collet, S., Guillamo, J. S., Hossu, G., Lacombe, S., Gauduel, Y. A., Levin, C. H., Dou, W., Ruan, S., Barre, L., Rioult, F., Derlon, J. M., Lechapt-Zalcman, E., Valable, S., Chapon, F., Courtheoux, P., Fong, V., & Kauffmann, F. (2011). Effects of reactive oxygen species on metabolism monitored by longitudinal H-1 single voxel MRS follow-up in patients with mitochondrial disease or cerebral tumors. In COST CHEMISTRY CM0603-MELUSYN JOINT MEETING: DAMAGES INDUCED IN BIOMOLECULES BY LOW AND HIGH ENERGY RADIATIONS (Vol. 261).
Résumé: Free radicals, or Reactive Oxygen Species (ROS), have an effect on energy and glycolytic metabolism, mitochondrial function, lipid metabolism, necrosis and apoptosis, cell proliferation, and infiltration. These changes could be monitored longitudinally (every 4 months over 6 years) in humans with glial brain tumors (low and high grade) after therapy, using conventional magnetic resonance imaging (MRI) and spectroscopy (MRS) and MR perfusion. Some examples of early clinical data from longitudinal follow-up monitoring in humans of energy and glycolytic metabolism, lipid metabolism, necrosis, proliferation, and infiltration measured by conventional MRI, MRS and perfusion, and positron emission tomography (PET) are shown in glial brain tumors after therapy. Despite the difficulty, the variability and unknown factors, these repeated measurements give us a better insight into the nature of the different processes, tumor progression and therapeutic response.
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Oubekka, S. D., Briandet, R., Waharte, F., Fontaine-Aupart, M. - P., & Steenkeste, K. (2011). Image-based Fluorescence Recovery After Photobleaching (FRAP) to dissect vancomycin diffusion-reaction processes in Staphylococcus aureus biofilms. In CLINICAL AND BIOMEDICAL SPECTROSCOPY AND IMAGING II (Vol. 8087).
Résumé: The diffusion capabilities of free fluorophores inside the heterogeneous three dimensional structure of Staphylococcus aureus biofilm were studied by an original image-based Fluorescence Recovery After Photobleaching method. The study was extended to BODIPY-vancomycin in order to better understand the mechanisms involved in the high tolerance of the bacteria embedded in a biofilm to the antibiotic.
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Parent, P., Laffon, C., Bournel, F., Lasne, J., & Lacombe, S. (2011). NEXAFS: a unique tool to follow the photochemistry of small organic molecules in condensed water. In COST CHEMISTRY CM0603-MELUSYN JOINT MEETING: DAMAGES INDUCED IN BIOMOLECULES BY LOW AND HIGH ENERGY RADIATIONS (Vol. 261).
Résumé: Soft X ray induced chemistry of simple organic molecules as carbon monoxide (CO), methanol (CH(3)OH) and glycine (NH(3)CH(2)COOH) in water and nitric acid hydrate has been investigated with NEXAFS spectroscopy. In the pure species, extremely high survival rates are observed, a consequence of the back reactions allowed in the condensed phase. When mixed with water, the survival rates are considerably reduced by reaction with the hydroxyl radical (OH). The formation of CO(2) is also enhanced at the expense of CO, the main byproduct in the photolysis of the pure species. Finally, it is shown that water plays no role in the destruction of the amino acid.
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Porcel, E., Kobayashi, K., Usami, N., Remita, H., Le Sech, C., & Lacombe, S. (2011). Photosensitization of plasmid-DNA loaded with platinum nano-particles and irradiated by low energy X-rays. In COST CHEMISTRY CM0603-MELUSYN JOINT MEETING: DAMAGES INDUCED IN BIOMOLECULES BY LOW AND HIGH ENERGY RADIATIONS (Vol. 261).
Résumé: Damage in DNA plasmids (pBR322) loaded with platinum nanoparticles (NP-Pt) DNA-NP and irradiated with monochromatic X-rays tuned to the resonant photoabsorption energy of the L(III) and M(III) electronic inner-shell of platinum – respectively 11556 eV and 2649 eV – and off-resonant X-rays – 11536 eV and 2639 eV- is investigated. In all the experiments, an enhancement of the single and double strand break – SSB and DSB – yields is observed when NP-Pt are present. Amplification effects are almost similar for the irradiations performed at on and off the L or M shell resonance suggesting that a non resonant mechanism is responsible for the major part of the DNA breaks enhancement. The amount of DNA breaks measured in the present work is compared to the results in similar experiments made with complexes of plasmid-DNA containing platinum molecule : chloroterpyridine platinum (PtTC). The average number of PtTC molecules in the solution is the same as in the experiments made with NP-Pt in order to study a possible difference in the radiosensitization efficiency when the high-Z atoms are clustered (NP-Pt) or dispersed in the system (PtTC). A mechanism is suggested involving photoelectrons which can efficiently ionize the platinum atoms. These results are consistent with those observed when DNA-NP complexes are irradiated by fast atomic ions. These findings suggest that any nanoparticle made of high-Z atoms might behaves as radiation enhancer whatever the ionizing radiation is electromagnetic or charged particle source.
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