  Magnetic nanoparticles have a broad spectrum of biomedical applications
including cell separation, diagnostics and therapy. One key issue is little
explored: how do the engineered nanoparticles interact with blood components
after injection? The formation of bioconjugates in the bloodstream and
subsequent reactions are potentially toxic due to the ability to induce an
immune response. The understanding of the underlying processes is of major
relevance to design not only efficient, but also safe nanoparticles for
targeted drug delivery applications. In this study, we report on maghemite
nanoparticles functionalized with citrate, dextran and polyethylene glycol
coatings and their interaction with the clotting protein fibrinogen. Further,
we investigate using biophysical tools (e.g. dynamic light scattering, circular
dichroism spectroscopy and quartz crystal microbalance) the interaction of the
magnetic nanoparticles-fibrinogen bioconjugates with artificial cell membranes
as a model system for blood platelets. We found that fibrinogen corona
formation provides colloidal stability to maghemite nanoparticles. In addition,
bioconjugates of fibrinogen with dextran and citrate coated NPs interact with
integrin containing lipid bilayer, especially upon treatment with divalent
ions, whereas PEG-coating reveals minor interaction. Our study at the interface
of protein-conjugated nanoparticles and artificial cell membranes is essential
for engineering safe nanoparticles for drug delivery applications.
