SURFACE MODIFICATION OF SUPERPARAMAGNETIC NANOPARTICLES (FERROFLUID) STUDIED WITH PARTICLE ELECTROPHORESIS - APPLICATION TO THE SPECIFIC TARGETING OF CELLS

Colloidal aqueous suspension of superparamagnetic nanoparticles (9 nm in diameter) composed of maghemite (gamma Fe2O3) and forming an ionic ferrofluid in aqueous solution are covalently coupled with lectins, en zymes or antibodies, using specific thiol chemistry. The surface charg e modifications of nanoparticles, caused by ligand coupling, were moni tored by measuring their electrophoretic mobilities using laser-Dopple r velocimetry. Particle electrophoretic mobility (PEM) changes are sho wn to correlate well with the amount of ligand fixed on the particles, as probed by its biological activity. The PEM method provides a usefu l tool to optimize ligand immobilization at the surface of nanoparticl es, and may be advantageous when biological activity measurements are not convenient.