Novel Nanoparticle Formulations with Enhanced F Relaxation

Introduction Fluorine MRI is receiving increasing attention, primarily due to the high NMR sensitivity of F nuclei, the physiological absence of fluorine containing substances and the availability of contrast materials based on bio-compatible perfluorinated carbon (PFC) nanostructures. The applicability of F MR as a molecular and cellular imaging technique has been demonstrated in a number of studies ranging from in vivo cell tracking to detection and imaging of tumors in small animals. Besides applications, developing new contrast materials with improved relaxation properties has also been a core research topic in the field, since the inherently low longitudinal relaxation rates of PFC compounds result in to relatively low imaging efficiencies. Borrowed from H MRI, the incorporation of Lanthanides, specifically Gd(III)-complexes, as signal modulating ingredients into the nanoparticle formulation has emerged as a promising approach towards improvement of the Fluorine signal. In this paper we present three different F nanoparticle formulations where perfluoro-15-crown-5-ether has been used as the core material and Gd(III)-DOTADSPE, Gd(III)-DOTA-C6-DSPE and Gd(III)-DTPA-BSA (Figure 1) as the relaxation altering components. Single voxel spectroscopy based T1 measurements conducted at 3.0T revealed enhanced relaxation in all three compositions with respect to a reference sample consisting of Gadolinum-free PFCE nanoparticles.