Biomedical Engineering Reference
In-Depth Information
Gadolinium oxide nanocrystals may also be coated using PEG-silane derivatives,
with such treatment resulting in an enhanced relaxivity whilst preventing aggrega-
tion of the oxide cores [26] . A dopamine - PEG - based ligand was synthesized and
used to coat 9 nm magnetite nanoparticles under physiological conditions; this
resulted in the formation of a stable ferrofl uid (Figure 4.2), which was found
subsequently to be a promising contrast agent for MRI [95]. In another study,
trifl uoroethylester - terminal - PEG - silane was self - assembled on iron oxide nano-
particles, allowing subsequent conjugation with cell-targeting agents (in this case,
folic acid) via carboxylic or amine terminal groups [91]. Folic acid was also conju-
gated to bifunctional PEG coatings on SPIONs; this resulted in nanoconjugates
that could serve as MRI contrast agents targeted at the detection of cancer cells
that overexpressed the folate receptor [94] . New antibiofouling polymer - coated iron
oxide nanoparticles have been developed using a copolymeric system comprising
a “ surface anchoring moiety ” (silane group) and a “ protein - resistant moiety ”
(PEG), denoted as poly- (TMSMA - r - PEGMA). These nanomaterials demonstrated
good potential as MRI contrast agents for tumor detection [98]. Other PEG block
copolymers used to stabilize magnetic nanoparticles for MRI applications include
poly(poly(ethyleneglycol) monomethacrylate) [96] and poly(ethylene oxide) - block -
poly(glutamic acid) [99] .
Fe
3
O
4
COOH
Fe
3
O
4
COOH
O
O
X
OH
X
O
COOH
n
O
Oleylamine & oleic acid
OH
OH
NH
Figure 4.2
Surface modifi cation of Fe
3
O
4
nanoparticles via
DPA - PEG - COOH. X = CH
2
NHCOCH
2
CH
2
for PEG3000,
PEG6000, PEG20000. X is not present in PEG600; the bonds
on both sides of the X are directly linked. Reproduced from
Ref. [95] .
