The effective application of magnetic nanoparticles in-vivo requires a complete understanding of their behavior and interactions in differing environments. Superparamagnetic nanoparticles are promising candidates for biomedical applications due to their high susceptibility and zero coercivity, by definition. In the presence of an applied magnetic field superparamagnetic nanoparticles are known to form chains, where the giant coherent spins align with the direction of the field. In the absence of an applied field superparamagnetic nanoparticles have been shown to form rings, or flux closure loops; however, these are typically discovered upon drying and do not necessarily represent behavior in solution. Recent analysis using small angle neutron scattering (SANS) showed that superparamagnetic Fe3O4 nanoparticles coated in a hydrophilic polymer exist as dimers or higher order aggregates in solution. To further investigate this we performed cryogenic transmission electron microscopy (cryo-TEM) experiments to capture a snapshot of the behavior in solution. We show that dimers and longer chain length structures do exist, confirming the observation in SANS. Furthermore, we observe unique arrangements of the nanoparticles which are not captured in scattering experiments, indicating cryo-TEM is a powerful tool for investigating nanoparticle interactions in solution.

Investigating magnetic nanoparticle interactions with Cryo-TEM

2019 Spring National Meeting

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