Insight into Serum Protein Interactions with Functionalized
Magnetic Nanoparticles in Biological Media
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Abstract
Surface modification with linear polymethacrylic acid (20 kDa),
linear and branched polyethylenimine (25 kDa), and branched oligoethylenimine
(800 Da) is commonly used to improve the function of magnetite nanoparticles
(MNPs) in many biomedical applications. These polymers were shown
herein to have different adsorption capacity and anticipated conformations
on the surface of MNPs due to differences in their functional groups,
architectures, and molecular weight. This in turn affects the interaction
of MNPs surfaces with biological serum proteins (fetal bovine serum).
MNPs coated with 25 kDa branched polyethylenimine were found to attract
the highest amount of serum protein while MNPs coated with 20 kDa
linear polymethacrylic acid adsorbed the least. The type and amount
of protein adsorbed, and the surface conformation of the polymer was
shown to affect the size stability of the MNPs in a model biological
media (RPMI-1640). A moderate reduction in <i>r</i><sub>2</sub> relaxivity was also observed for MNPs suspended in RPMI-1640
containing serum protein compared to the same particles suspended
in water. However, the relaxivities following protein adsorption are
still relatively high making the use of these polymer-coated MNPs
as Magnetic Resonance Imaging (MRI) contrast agents feasible. This
work shows that through judicious selection of functionalization polymers
and elucidation of the factors governing the stabilization mechanism,
the design of nanoparticles for applications in biologically relevant
conditions can be improved