Preparation and medical application of magnetic beads conjugated with bioactive molecules

Ferrite nanobeads were synthesized from an aqueous solution utilizing Fe2+ to Fe3+ oxidation for use as magnetic carriers in bioscreening, bio-molecular recognition and anti-cancer diagnosis and therapy. The beads had a crystal structure that was intermediate between Fe3O4 and gamma-Fe2O3. Functional biomolecules were strongly conjugated onto the surfaces of the ferrite beads via COOH and SH groups. The addition of ferrite seed crystals (3-8 nm in size) together with a disaccharide enabled the synthesis of monodisperse, spherical ferrite beads with average diameters ((d) over bar) between 50 and 150 nm and relative deviation Delta d/(d) over bar = 9-16%. Hollow ferrite nano-spheres ((d) over bar 150-450 nm, Delta d/(d) over bar approximate to 10%) were prepared using silica spheres as templates, which were dissolved in NaOH solution. Ferrite beads 40 nm in size were encapsulated in polymer spheres of styrene and polymerized glycidyl methacrylate (poly-GMA), 18479 nm in diameter. They were used for high throughput bioscreening system for affinity purification of target proteins which make specific bindings to anti-cancer drugs, porphyrins, environment hormones, etc. (C) 2008 Elsevier B. V. All rights reserved.