Use of magnetic field for addressing, grafting onto support and actuating permanent magnetic filaments applied to enhanced biodetection
Résumé
A simple method combining magnetic field and microparticles has been designed for assembling, locating and grafting permanent microfilaments onto a silanised glass surface. Filaments orthogonal to a glass support are implemented by assembling magnetic carboxylatex particles under magnetic field. They exhibit an aspect ratio up to 14. Carboxyl moieties on beads and silanised glass are activated using the carbodiimide method. A further reaction with long chain diamines allows the formation of permanent filaments covalently anchored onto the glass support. Grafted microfilaments can withstand intense washing with detergent solutions under ultrasound. 500 mm diameter filament spots are formed using ferromagnetic tips connected to an electromagnet. After their formation, filaments can be actuated by an external magnetic field: their orientation is tunable in real time within a 2 pi solid angle. Filaments can be biofunctionalised in order to perform biomolecular recognition on the support. We show that nucleic acid probes immobilised onto these filaments hybridize with labelled oligonucleotide targets. Due to an increase of the specific surface, the fluorescence signal of targets is 3-fold higher with filaments than with a planar glass support biofunctionalised with the same oligonucleotides. Our methodology thus provides an easy way to create filaments usable for both actuation and biodetection onto a planar support. We expect our strategy to be compatible with the formation of nanofilaments using nanoparticles.