(286d) The Influence of the Stabilizing Polymer Brush On Transverse Relaxation Rates in Magnetic Resonance Imaging: Implications of Interparticle Interactions

There have been significant advances recently in the use of magnetic nanoparticles for various biomedical applications, with one potential use as contrast enhancement agents in magnetic resonance imaging (MRI).¹ In order to study the effect chain formation on MRI contrast enhancement and its relationship with the stabilizing brush length, a matrix of 22nm particles with varied ligand lengths was synthesized using iron oxide particles with poly(ethylene glycol) ligands. These systems were characterized with dynamic light scattering, transmission electron microscopy, dark-field scattering, and proton transverse relaxation measurements. The dark field scattering experiments and transverse relaxation measurements were done in a similar magnetic field under the same time scale to correlate the reduction of the transverse relativity with the formation of linear magnetic chains.  Our results suggest that varying the ligand length has a direct effect on the transverse relaxation mechanism due to the contribution of ligand length to the colloidal stability of the system, including differences in chain formation rate and size.  With increasing ligand length, interparticle interactions are limited, which results in slower chain formation and shorter widespread chains.  This data indicates that understanding the colloidal arrangement of these systems is paramount, and that both particle stability and time dependence both play a key role in determining the effect of iron oxide nanoparticles on surrounding water protons. 

            In this talk we will discuss the synthesis of unique heterobifunctional polymers, magnetite particle synthesis and functionalization, as well as calculations of interparticle interaction based on a modified DLVO theory. 

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2.         Carroll, M. R. J.; Huffstetler, P. P.; Miles, W. C.; Goff, J. D.; Davis, R. M.; Riffle, J. S.; House, M. J.; Woodward, R. C.; St Pierre, T. G., The effect of polymer coatings on proton transverse relaxivities of aqueous suspensions of magnetic nanoparticles. Nanotechnology 2011, 22, (32).

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