Magnetofluorescent micellar complexes of terbium(III) as potential bimodal contrast agents for magnetic resonance and optical imaging

Terbium(III) was coordinated to four novel 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) amphiphilic bisamide ligands. The complexes were assembled intomono-disperse micellar nano-aggregates and for the first time Tb-III has been evaluated as a single lanthanide negative bimodal contrast agent for MRI/OI. The complexes show characteristic Tb-III emission with quantum yields reaching 7.3% and transverse relaxivity r(2) per Tb-III micelle at 500 MHz and 310 K reaches maximum values up to 60 s(-1) micelle(-1). The efficient T-2 relaxation at high magnetic field strengths is sustained by the increased rotational correlation time of the nano-aggregates and high magnetic moment of the terbium ion.