000166945 001__ 166945
000166945 005__ 20190316235145.0
000166945 0247_ $$2doi$$a10.5075/epfl-thesis-5139
000166945 02470 $$2urn$$aurn:nbn:ch:bel-epfl-thesis5139-1
000166945 02471 $$2nebis$$a6492059
000166945 037__ $$aTHESIS
000166945 041__ $$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 909C0 $$0252090$$pLEPA$$xU10100
000166945 909CO $$ooai:infoscience.tind.io:166945$$pthesis-bn2018$$pDOI$$pSB$$pthesis$$qDOI2$$qGLOBAL_SET
000166945 918__ $$aSB$$cISIC$$dEDCH
000166945 919__ $$aLEPA
000166945 920__ $$b2011
000166945 970__ $$a5139/THESES
000166945 973__ $$aEPFL$$sPUBLISHED
000166945 980__ $$aTHESIS