AVS 51st International Symposium
    Magnetic Interfaces and Nanostructures Tuesday Sessions
       Session MI-TuA

Invited Paper MI-TuA1
Synthesis and Surface Modification of Monodisperse Magnetic Nanoparticles for Biological Applications

Tuesday, November 16, 2004, 1:20 pm, Room 304A

Session: BioMagnetism
Presenter: S. Sun, IBM T.J. Watson Research Center
Authors: S. Sun, IBM T.J. Watson Research Center
H. Zeng, IBM T.J. Watson Research Center
H. Yu, IBM T.J. Watson Research Center
D. Robinson, IBM T.J. Watson Research Center
G. Li, Stanford University
S. Wang, Stanford University
R. White, Stanford University
Correspondent: Click to Email
We present our chemical synthesis and surface modification of monodisperse magnetic nanoparticles for potential applications in bio-recognition. Biocompatible dispersions of magnetic nanoparticles have been used widely in bimolecular labeling and biological imaging, sensing and separation in recent years. These applications require that the particles be superparamagnetic at room temperature, and monodisperse for uniform biodistribution, bioelimination and contrast effects. The Co and Fe based magnetic nanoparticles, including metallic Co, Fe, CoFe and oxide MFe2O4 nanoparticles, have high magnetic moment, and thus sufficient sensitivity for magnetic detection. With proper functionalization, they can be useful candidates as magnetic probes for biomolecule identification. We have developed various synthetic procedures for making monodisperse magnetic nanoparticles. Using a combination of surfactants, such as oleic acid/oleyl amine, to control nanoparticle growth and stabilization, we can tune the size of the nanoparticles to obtain an optimum magnetic signal for sensor detection. By controlling particle surface chemistry and synthetic conditions, we can also produce multi-functional nanoparticles with either core/shell-structured particles, such as Fe3O4/AgSe or Fe3O4/FePt, or dumbbell-structured particles, such as Fe3O4-Ag. We can further transform the oleic acid/oleylamine capped, hydrophobic nanoparticles into hydrophilic ones by using tetramethylammonium hydroxide, bi-functional thiol molecules, or multi-functional polymeric molecules. These hydrophilic nanoparticles are both chemically and magnetically stable in phosphate buffer solution at neutral pH, and can withstand DNA denaturing and hybridization conditions. They are suitable as magnetic probes for highly sensitive bio-detection. Acknowledgement: The work is supported in part by DARPA under grant No. N00014-01-1-0885.