Biomedical Engineering Reference
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Fig. 9.4 Highly stable polymer coating on MNPs .( a ) Hydrophobic layers on MNPs were
first replaced with TMAH (tetramethylammonium hydroxide) and then further coated with
carboxymethyl polyvinyl alcohol (CMPVA). TEM confirms that the particles are well dispersed
in water after the CMPVA coating. ( b ) The presence of carboxylic acids on polyvinyl alcohol
(PVA) is crucial to the stability of the coating; PVA-coated MNPs aggregated in aqueous solutions.
( c ) Cancer cells (SkBr3) were labeled with fluorescent CMPVA-MNPs by targeting HER2/neu
surface receptors. CMPVA coating displayed remarkably low nonspecific binding to the cells
(Reproduced from [ 46 ]. Copyright 2010 John Wiley and Sons, Inc.)
allow CMPVA to strongly bind to the metal oxide surface. Indeed, when hydropho-
bic MnFe 2 O 4 MNPs were coated with CMPVA, the particles showed excellent,
long-term solubility (>12 months) in aqueous buffers, whereas PVA-coated par-
ticles precipitated spontaneously (Fig. 9.4 b). CMPVA coating also provided free
amine .
NH 2 / groups for bioconjugation.
When tested for cellular labeling, the CMPVA coating exhibited extremely
low nonspecific binding. Figure 9.4 c shows an example of cellular labeling with
CMPVA-MNPs. Cancer cells (SkBr3) were first labeled with biotinylated anti-
HER2/ neu monoclonal antibodies, followed by an incubation with neutravidin-
modified, fluorescent CMPVA-MNPs. Control samples were prepared in the same
way but without antibody injection. Strong fluorescence signal could be visualized
on the surface of targeted cells, whereas the signal from control samples was
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