Université PSL



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Surface Reactivity from Electrochemical Lithography: Illustration in the Steady-State Reductive Etching of Perfluorinated Surfaces
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - H. Hazimeh, S. Nunige, R. Cornut, C. Lefrou, C. Combellas, F. Kanoufi
Anal. Chem. - 83(15) :6106-13 - DOI:10.1021/ac201255c - 2011
The scanning electrochemical microscope (SECM) in the lithographic mode is used to assess quantitatively, from both theoretical and experimental points of view, the kinetics of irreversible transformation of electroactive molecular moieties immobilized on a surface as self-assembled monolayers (SAMs). The SECM tip allows the generation of an etchant that transforms the surface locally and irreversibly. The resulting surface patterning is detectable by different surface analyses. The quantification of the surface transformation kinetics is deduced from the evolution of the pattern dimensions with the etching time. The special case of slow etching kinetics is presented; it is predicted that the pattern evolution follows the expansion of the etchant at the substrate surface. The case of a chemically unstable etchant is considered. The model is then tested by inspecting the slow reductive patterning of a perfluorinated SAM. Good agreement is found with different independent SECM interrogation modes, depending on the insulating or conducting nature of the covered substrate. The surface transformation measurements are also compared to the reduction of solutions of perfluoroalkanes. The three-orders-of-magnitude-slower electron transfer observed at the immobilized molecules likely describes the large reorganization associated with the generation of a perfluoroalkyl-centered radical anion.
Feasibility of ultra high performance supercritical neat carbon dioxide. chromatography at conventional pressures
Laboratoire Sciences Analytiques Bioanalytiques et Miniaturisation - C. Sarazin, D. Thiebaut, P. Sassiat,J. Vial
J. Sep. Sci. - 34(19) :2773-8 - DOI:10.1002/jssc.201100332 - 2011
The implementation of columns packed with sub-2 µm particles in supercritical fluid chromatography (SFC) is described using neat carbon dioxide as the mobile phase. A conventional supercritical fluid chromatograph was slightly modified to reduce extra column band broadening. Performances of a column packed with 1.8 µm C18-bonded silica particles in SFC using neat carbon dioxide as the mobile phase were compared with results obtained in ultra high performance liquid chromatography (UHPLC) using a dedicated chromatograph. As expected and usual in SFC, higher linear velocities than in UHPLC must be applied in order to reach optimal efficiency owing to higher diffusion coefficient of solutes in the mobile phase; similar numbers of theoretical plates were obtained with both techniques. Very fast separations of hydrocarbons are presented using two different alkyl-bonded silica columns.
Differential RNA-binding activity of the hnRNP G protein correlated with the sex genotype in the amphibian oocyte
Laboratoire Spectrométrie de masse biologique et protéomique - Kanhoush, R; Praseuth, D; Perrin, C; Chardard, D; Vinh, J; Penrad-Mobayed, M.
Nucleic Acids Res. - 39(10) :4109-21 - DOI:10.1093/nar/gkq1315 - 2011
A proteomic approach has enabled the identification of an orthologue of the splicing factor hnRNP G in the amphibians Xenopus tropicalis, Ambystoma mexicanum, Notophthalmus viridescens and Pleurodeles walt, which shows a specific RNA-binding affinity similar to that of the human hnRN G protein. Three isoforms of this protein with a differential binding affinity for a specific RNA probe were identified in the P. walt oocyte. In situ hybridization to lampbrush chromosomes of P. waltl revealed the presence of a family of hnRNP G genes, which were mapped on the Z and W chromosomes and one autosome. This indicates that the isoforms identified in this study are possibly encoded by a gene family linked to the evolution of sex chromosomes similarly to the hnRNP G/RBMX gene family in mammals.
T Cells Recognizing a Peptide Contaminant Undetectable by Mass Spectrometry
Laboratoire Spectrométrie de masse biologique et protéomique - Brezar V, Culina S, Osterbye T, Guillonneau F, Chiappetta G, Verdier Y, Vinh J, Wong FS, Buus S, Mallone R.
PLoS One - 6(12) :e28866 - DOI:10.1371/journal.pone.0028866 - 2011
Synthetic peptides are widely used in immunological research as epitopes to stimulate their cognate T cells. These preparations are never completely pure, but trace contaminants are commonly revealed by mass spectrometry quality controls. In an effort to characterize novel major histocompatibility complex (MHC) Class I-restricted ß-cell epitopes in non-obese diabetic (NOD) mice, we identified islet-infiltrating CD8+ T cells recognizing a contaminating peptide. The amount of this contaminant was so small to be undetectable by direct mass spectrometry. Only after concentration by liquid chromatography, we observed a mass peak corresponding to an immunodominant islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP)206-214 epitope described in the literature. Generation of CD8+ T-cell clones recognizing IGRP206-214 using a novel method confirmed the identity of the contaminant, further underlining the immunodominance of IGRP206-214. If left undetected, minute impurities in synthetic peptide preparations may thus give spurious results.
Reversed-phase HPLC and hyphenated analytical strategies for peptidomics
Laboratoire Spectrométrie de masse biologique et protéomique - Hesse AM, Ndiaye S, Vinh J.
Methods Mol Biol. - 789 :203-21 - DOI:10.1007/978-1-61779-310-3_13. - 2011
Peptide study and analysis widely involve liquid chromatography. Among the different strategies available, reversed-phase liquid chromatography (RP-HPLC) is one of the methods of choice to separate species in a nontargeted approach. The compounds are sorted according to their hydrophobicity, even though the experimental order of elution could change according to the nature of the mobile phase and the stationary phase. In our work, we have developed protocols to resolve hundred of peptidic species. To overcome the limitations of peak capacity of RP-HPLC alone, it has been coupled downstream to tandem mass spectrometry using two different ionization modes. To overcome the limitations of peak capacity of RP-HPLC MS/MS, it has been coupled upstream to strong cation exchange liquid chromatography. Multidimensional analysis allows for a deeper description of a sample because the limit of detection is often due to a lack of dynamic range of the detection itself rather than due to a lack of sensitivity. In this chapter, different protocols are presented. They should be considered as examples that could be used as starting point for new protocols optimization. Even if RP-HPLC is a universal peptide separation method, it should be optimized according to the specific characteristics of the peptide(s) of interest.
Microchip integrating magnetic nanoparticles for allergy diagnosis
Laboratoire Synthèse Electrochimie Imagerie et Systèmes Analytiques - Teste B, Malloggi F, Siaugue JM, Varenne A, Kanoufi F, Descroix S.
Lab. Chip - 11(24) :4207-13 - DOI:10.1039/c1lc20809h - 2011
We report on the development of a simple and easy to use microchip dedicated to allergy diagnosis. This microchip combines both the advantages of homogeneous immunoassays i.e. species diffusion and heterogeneous immunoassays i.e. easy separation and preconcentration steps. In vitro allergy diagnosis is based on specific Immunoglobulin E (IgE) quantitation, in that way we have developed and integrated magnetic core-shell nanoparticles (MCSNPs) as an IgE capture nanoplatform in a microdevice taking benefit from both their magnetic and colloidal properties. Integrating such immunosupport allows to perform the target analyte (IgE) capture in the colloidal phase thus increasing the analyte capture kinetics since both immunological partners are diffusing during the immune reaction. This colloidal approach improves 1000 times the analyte capture kinetics compared to conventional methods. Moreover, based on the MCSNPs' magnetic properties and on the magnetic chamber we have previously developed the MCSNPs and therefore the target can be confined and preconcentrated within the microdevice prior to the detection step. The MCSNPs preconcentration factor achieved was about 35,000 and allows to reach high sensitivity thus avoiding catalytic amplification during the detection step. The developed microchip offers many advantages: the analytical procedure was fully integrated on-chip, analyses were performed in short assay time (20 min), the sample and reagents consumption was reduced to few microlitres (5 µL) while a low limit of detection can be achieved (about 1 ng mL(-1)).
On-chip multi-electrochemical sensor array platform for simultaneous screening of nitric oxide and peroxynitrite
Laboratoire Synthèse Electrochimie Imagerie et Systèmes Analytiques - Quinton D., Girard A., Kim LTT., Raimbault V., Griscom L., Razan F., Griveau S., Bedioui F.
Lab. Chip - 11 :1342-50 - DOI:10.1039/c0lc00585a - 2011
In this work we report on the design, microfabrication and analytical performances of a new electrochemical sensor array (ESA) which allows for the first time the simultaneous amperometric detection of nitric oxide (NO) and peroxynitrite (ONOO(-)), two biologically relevant molecules. The on-chip device includes individually addressable sets of gold ultramicroelectrodes (UMEs) of 50 µm diameter, Ag/AgCl reference electrode and gold counter electrode. The electrodes are separated into two groups; each has one reference electrode, one counter electrode and 110 UMEs specifically tailored to detect a specific analyte. The ESA is incorporated on a custom interface with a cell culture well and spring contact pins that can be easily interconnected to an external multichannel potentiostat. Each UME of the network dedicated to the detection of NO is electrochemically modified by electrodepositing thin layers of poly(eugenol) and poly(phenol). The detection of NO is performed amperometrically at 0.8 V vs. Ag/AgCl in phosphate buffer solution (PBS, pH = 7.4) and other buffers adapted to biological cell culture, using a NO-donor. The network of UMEs dedicated to the detection of ONOO(-) is used without further chemical modification of the surface and the uncoated gold electrodes operate at -0.1 V vs. Ag/AgCl to detect the reduction of ONOOH in PBS. The selectivity issue of both sensors against major biologically relevant interfering analytes is examined. Simultaneous detection of NO and ONOO(-) in PBS is also achieved.
Magnetic core shell nanoparticles trapping in a microdevice generating high magnetic gradient
Laboratoire Synthèse Electrochimie Imagerie et Systèmes Analytiques - Teste B, Malloggi F, Gassner AL, Georgelin T, Siaugue JM, Varenne A, Girault H, Descroix S.
Lab. Chip - 11(5) :833-40 - DOI:10.1039/c0lc00510j - 2011
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 µm 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 µL h(-1), the nanoparticles trapping/release can be achieved within 20 s with a preconcentration factor of 4000.
Determination of binding parameters between lysozyme and its aptamer by frontal analysis continuous microchip electrophoresis (FACMCE)
Laboratoire Synthèse Electrochimie Imagerie et Systèmes Analytiques - Girardot M, Li HY, Descroix S, Varenne A.
J. Chrom. A - 1218 :4052-8 - DOI:10.1016/j.chroma.2011.04.077 - 2011
An original and simple methodology based on microchip electrophoresis (MCE) in a continuous frontal analysis mode (named frontal analysis continuous microchip electrophoresis, FACMCE) was developed for the simultaneous determination of the binding parameters, i.e. ligand-site dissociation constant (k(d)) and number of binding sites on the substrate (n). This simultaneous determination was exemplified with the interaction between an aptamer and its target. The selected target is a strongly basic protein, lysozyme, as its quantification is of great interest due to its antimicrobial and allergenic properties. A glass microdevice equipped with a fluorescence detection system was coated with hydroxypropylcellulose, reducing the electroosmotic flow and adsorption onto the channel walls. This microdevice allowed the continuous electrokinetic injection of a mixture of fluorescently labelled aptamer and non-labelled lysozyme. By determining the concentration of the free fluorescently labelled aptamer thanks to its corresponding plateau height, mathematical linearization methods allowed to determine a k(d) value of 48.4±8.0 nM, consistent with reported results (31 nM), while the average number of binding sites n on lysozyme, never determined before, was 0.16±0.03. These results seem to indicate that the buffer nature and the SELEX process should influence the number and affinity of the binding sites. In parallel it has been shown that the binding between lysozyme and its aptamer presents two sites of different binding affinities.
Microelectrochemical patterning of gold surfaces using 4-azidobenzenediazonium and scanning electrochemical microscopy
Laboratoire Synthèse Electrochimie Imagerie et Systèmes Analytiques - Coates M., Cabet E., Griveau S., Nyokong T., Bedioui F.
Electrochemistry Communications - 13 :150-3 - DOI:10.1016/j.elecom.2010.11.037 - 2011
This work describes for the first time the possibility of performing local micro electrochemical grafting of a gold substrate by 4-azidobenzenediazonium by SECM in a single and simple one step without complications from adsorption. The electrografted spots of diazonium were performed by positioning a Pt tip at a given distance above the gold substrate and the SECM was used in a three-electrode configuration (the Pt tip serving as the microanode) in acetonitrile containing 5 mM 4-azidobenzenediazonium and 0.1 M Bu4NBF4 during 10 ms. The dimensions of the derivatized areas of the substrates were finely tuned by using different experimental conditions (tip distance above the substrate, tip diameter, presence or absence of supporting electrolyte). The use of the azido-derivated diazonium molecule and these preliminary results open the gate to important applications and developments devoted to the local micro functionalization of electrodes by thin layers that allow the implementation of the emerging and attractive interfacial click reaction.

391 publications.