000166945 001__ 166945
000166945 005__ 20180317094724.0
000166945 0247_ $$2doi$$a10.5075/epfl-thesis-5139
000166945 02470 $$2urn$$aurn:nbn:ch:bel-epfl-thesis5139-1
000166945 02471 $$2nebis$$a6492059
000166945 037__ $$aTHESIS_LIB
000166945 041__ $$aeng
000166945 088__ $$a5139
000166945 245__ $$aMagnetic Stationary Phases for Protein Adsorption
000166945 269__ $$a2011
000166945 260__ $$aLausanne$$bEPFL$$c2011
000166945 300__ $$a176
000166945 336__ $$aTheses
000166945 520__ $$aMagnetic beads (MB) have now proven to be a powerful tool       in both research and biomedical applications. They are       available in a wide range of sizes (from nm to several       µm) and their surface can be modified with molecules       having biological specificities and functions. The large       choice of functionalization developed over the last few years       covers non-specific interactions such as ionic or hydrophobic       ones, as well as group-specific interactions, like       immobilized metal affinity chromatography (IMAC) and,       finally, specific interactions such as antigen-antibody       recognition. In microfluidics, where the goals are faster       reaction time and reduced sample consumption, MB offer many       advantages. Firstly, compared to an open microchannel or an       empty capillary, a packed bed of beads increases the specific       surface available for molecule binding. The diffusion pathway       is thus significantly reduced, improving interactions between       molecules. Moreover, in comparison to classical beads, they       are easily manipulated by electromagnets or permanent       magnets. For these reasons, in this work they were chosen to       act as a solid support in a view of performing       immunoassays. As the literature often focuses mainly either on the       applications or on very advanced studies that are not       accessible to a non-specialist, it was difficult to find       information on the magnetic aspects such as the kind of       magnets, their number, their size or their arrangement.       First, a background study was dedicated to the understanding       of some basic magnetic aspects. The effect of the magnet       shape or the size on the magnetic induction and the magnetic       force was explored theoretically. Numerical simulations       showed the strength and location of the magnetic forces       versus three simple magnet configurations: two magnets       in attraction/repulsion or a single magnet and the results       were corroborated by microscopical visualizations. With this knowledge, it was then possible to enhance the       magnetic force. Indeed, if the magnetic force produced is too       weak, magnetic beads are unpredictably lost, resulting in       poorly reproducible results. Concretely, a new magnet       configuration using ring magnets, which are disks drilled       along their magnetization axis, was studied to increase the       magnetic force in a capillary, giving the opportunity to work       at higher flow rates and consequently decrease the       experimental time. This configuration also makes possible the       formation of a chain of magnets alternating with non-magnetic       spacers like a string of pearls, increasing in a controllable       manner the surface available for molecule binding. Adsorption is a fundamental process in immunoassays. As       antibodies are expensive reagents and as diagnostic tests       should be as least invasive as possible for the patient,       volumes should be reduced to their minimum. It is thus       essential to optimize adsorption by choosing the right       experimental parameters. In order to help the experimenter,       an abacus representation was proposed showing, for a given       surface coverage, the required binding time versus the flow       velocity in a microchannel with known dimensions. Then, the       question of knowing if the amount of analyte adsorbed is       increased with a surface divided into small patches relative       to a continuous surface for an equal total length was       raised. Then, the question of the amount of beads trapped was       handled as it also relates to the sensitivity of the       technique. In a capillary, the number of magnetic beads       possibly trapped is limited, particularly in small diameter       capillaries, e.g. 25 µm, as the capillary is       rapidly blocked as the plug size increases. In this work, a       simple bubble cell was used as a very convenient magnetic       bead trap where a large amount of beads can be spatially       immobilized without inducing a strong pressure drop, as it is       the case when magnetic beads are trapped in a standard       capillary. Finally, a sandwich-type immunoassay using magnetic beads       was developed for total IgE quantification in serum using the       Gravi™-Cell device from DiagnoSwiss. After the       determination of the optimal conditions, the method was       successfully applied to the measurement of total IgE in a       patient serum sample with a concentration in the same range       as those determined previously by two other methods.
000166945 6531_ $$amagnetic beads
000166945 6531_ $$aimmunoassays
000166945 6531_ $$acapillary electrophoresis
000166945 6531_ $$aadsorption
000166945 6531_ $$anumerical simulations
000166945 6531_ $$abilles magnétiques
000166945 6531_ $$aimmunoessais
000166945 6531_ $$aélectrophorèse capillaire
000166945 6531_ $$aadsorption
000166945 6531_ $$asimulations numériques
000166945 700__ $$0242742$$aGassner, Anne-Laure$$g167552
000166945 720_2 $$0242739$$aGirault, Hubert$$edir.$$g105258
000166945 8564_ $$s19785290$$uhttps://infoscience.epfl.ch/record/166945/files/EPFL_TH5139.pdf$$yTexte intégral / Full text$$zTexte intégral / Full text
000166945 909CO $$ooai:infoscience.tind.io:166945$$pSB$$pthesis$$pthesis-bn2018
000166945 909C0 $$0252090$$pLEPA$$xU10100
000166945 918__ $$aSB$$cISIC$$dEDCH
000166945 919__ $$aLEPA
000166945 920__ $$b2011
000166945 970__ $$a5139/THESES
000166945 973__ $$aEPFL$$sPUBLISHED
000166945 980__ $$aTHESIS