Co/Au Core-shell
Structures in Biomedical Application
Funding: NSF (DMR-0203069)
Project Summary:
Magnetic nanoparticles (NPs)
have potential applications in many biological
and medical applications such as drug delivery,
hyperthermia, magnetic resonance contrast enhancement
and cell separation. Even though biomcompatible
iron oxide NPs are the materials of choice,
there is significant interest in developing
alternative high moment cobalt (and related
alloys) for specific applications. The challenge
here is to prepare uniform, un-agglomerated
particles with controlled shapes and narrow
size distribution and coat them with an inert
shell for biocompatibility.
We have recently developed
a synthesis route involving the rapid decomposition
of metallorganic precursors in a surfactant
environment to prepare cobalt nanocrystals with
tailored sizes (dia ~ 5-25 nm) and controlled
shapes (spheres or disks)[1]. The latter is
accomplished by a judicious choice of surfactants
that adhere selectively to certain crystallographic
planes promoting anisotropic particle shapes.
Detailed magnetometry confirms the smaller particles
(d<10nm) to be superparamagnetic whilst the
larger ones (d >10 nm), and the disks, are
ferromagnetic.
To achieve biocompatibility
and water solubility, as well as explore the
potential application of these cobalt nanoparticles
in biology, we are synthesizing core-shell structures
of Cobalt-gold (core/shell ~ Au/Co or Co/Au).
Initial results on Au/Co and Co/Au are promising.
In addition chemical exchange of the surfactant
on the surface of the cobalt particles with
a functionalized polymer, such as polyethylene
glycol, to make them hydrophilic[2] has also
been accomplished.
[1] V. F. Puntes, Kannan M.
Krishnan and P.A. Alivisatos, Science, 291,
2115 (2001)
[2] Unpublished work in collaboration with Prof.
P. Stayton group, UW
Recent oral presentations:
Y. Bao, "Potential Applications
and Synthesis of Magnetic Nanoparticles",
Sept. 29, 2004, Nanoseminar Class, Chem 560B (UW).
Y. Bao, "A general approach
to synthesis of magnetic nanoparticles with different
morphologies", Sept. 16, 2004, Nanoscale
science and technology workshop (UW & PNNL)
Y. Bao, "Controlled synthesis
and self-assembly of cobalt-based nanoparticles",
May 24, 2004, UW Mat. Sci. Dept. Seminar
Kannan M. Krishnan, International
conference on Scientific and Clinical Applications
of Magnetic Carriers, Lyon, France, "Tailored
and functionalized cobalt nanocrystals for biomedical
applications", May 2004
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