Use of magnetic field for addressing, grafting onto support and actuating permanent magnetic filaments applied to enhanced biodetection

Abstract

International audienceA 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

Magnetically responsive polypyrrole nanotubes using Ce(III)-stabilized maghemite nanoparticles

“…Based on extensive literature examination, various noncovalent methods have been used for the fabrication of magnetite (Fe 3 O 4 )-CP NCs. Physical non-covalent interactions between the CP-based nanostructure and pre-formed magnetite/maghemite NPs mainly exploited emulsion polymerization [11], self-assembly [12][13][14][15][16], assembly of magnetic NPs into filaments [17,18], various templates [19,20], and template-free methods [21][22][23]. In addition, the CP-based nanostructure might be reacted with in situ generated magnetite/maghemite NPs using the basic hydrolysis of Fe 2+ /Fe +3 cation mixtures [20,24].…”

Elaboration and Grafting of Magnetic Bead-Chains for Detection of Anisotropy With Polarimetric Surface Plasmon Resonance Imaging System

“…In parallel, the characterization and the study of behavior of such objects required new tools adapted to the submicro or nanoscale. Here, we report a methodology based on the use of magnetic particles and their manipulation by a magnetic¯eld to self-assemble them into permanent¯laments 1,2 thanks to amine based chemistry. These permanent magnetic¯laments made from micro (1 m) or nano (200 nm) beads have been collectively addressed onto support on speci¯c area thanks to a selective chemical functionalization.…”