Biomedical Engineering Reference
In-Depth Information
together with a polymerizable derivative of PEG as a monomer [i.e., maleic
anhydride-modified PEG (MA-PEG)] and
N
,
N
0
-methylene bis acrylamide (MBA)
as crosslinking agent under nitrogen gas. Additional amounts of water may be
added in reverse micellar solution in order to obtain host micellar droplets of
desired size. In a typical experimental protocol, 50 mL of 0.05 M AOT solution
in hexane, 500 mL of magnetite solution (10 mg/mL), 100 mL of MA-PEG (5 mg/
mL), and 10 mL of MBA (0.5 mg/mL) were mixed. The solution was stable and
brownish transparent at this stage. Nitrogen gas was bubbled through this solution
to remove the dissolved oxygen. After 30 min, 20 mL of 2% ammonium persulfate
as an initiator was added. The polymerization of monomers was carried out by a
free radical polymerization mechanism at 37
C for 8 h. After polymerization, the
particles were purified from unreacted monomers.
Surface Modification of Magnetic Nanoparticles
Several surface modification methods have been tried for applications in drug
delivery and for MRI applications. A multifunctional magnetic nanoparticle
probe for deep tissue molecular MRI is shown in Fig.
22
. The magnetic nanoparti-
cle (5-10 nm in diameter) has an oligonucleotide hairpin probe on its surface. Cell-
penetrating peptides (for deep tissue delivery) and ligands (for targeting specific
cell types) are also conjugated on the nanoparticle surface. Binding of two or more
nanoparticle probes on an mRNA target inside a cell should generate a measurable
Fig. 22 Multifunctional magnetic nanoparticle probe for deep tissue molecular MRI. The mag-
netic nanoparticle (5-10 nm in diameter) has an oligonucleotide hairpin probe on its surface. Cell-
penetrating peptides (for deep tissue delivery) and ligands (for targeting specific cell types) are
also conjugated on the nanoparticle surface. Binding of two or more nanoparticle probes on an
mRNA target inside a cell should generate a measurable change in the MRI signal. Cells
expressing specific molecular markers of disease, infection, or injury are detected in this way.
(Credit: Gang Bao)
