Magnetic resonance imaging (MRI) is a powerful and ubiquitous tool for diagnostics. The information provided from MRI can be enhanced with contrast agents that respond to specific chemical events that are indicative of disease. The major limitation with most modern responsive contrast agents for MRI is a concentration-dependent response. Accordingly, contrast agents that respond in a concentration-independent manner are exceedingly important for diagnostic MRI. Here, we report the synthesis and characterization of a concentration-independent, oxidation-responsive liposomal contrast agent for MRI based on the redox chemistry of Eu. T1-weighted (positive) contrast enhancement is observed when Eu2+ is present in liposomes, and chemical exchange saturation transfer is observed after oxidation to Eu3+. Dynamic light scattering data reveal that the size distribution of the liposomes does not change after oxidation of Eu2+ to form Eu3+. Additionally, Eu remains encapsulated within liposomes before and after oxidation. The use of two orthogonal modes of contrast enhancement renders the concentration of Eu to be inconsequential to the molecular information provided through imaging. Concentration-independence coupled with redox response is expected to make redox-specific disease state imaging feasible in vivo.

Oxidation-responsive Eu<sup>2+/3+</sup>�liposomal contrast agent for dual-mode magnetic resonance imaging

248th National Meeting (2014)

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Oxidation-responsive Eu2+/3+�liposomal contrast agent for dual-mode magnetic resonance imaging

Oxidation-responsive Eu^2+/3+�liposomal contrast agent for dual-mode magnetic resonance imaging