Gadofullerenes as nanoscale magnetic labels for cellular MRI.

In this study, anionic gadofullerene {Gd@C60[C(COOH)2](10)} was used as an in vitro cellular magnetic resonance imaging label. The cellular uptake characteristics of this gadofullerene were significant and nonspecific, and excellent labeling efficiency (98-100%) was achieved without a transfecting agent. The average uptake was up to 133.6 +/- 5.5 pg Gd per cell or 10(11) Gd3+ ions per cell. The difference in the longitudinal relaxation time T(1) between labeled and unlabeled cells generated good contrast between labeled and unlabeled cells. A clinical magnetic resonance imaging imager at 1.5 T showed that signal intensity on the T(1) weighted magnetic resonance images was 250% greater in labeled cells. Thus, the anionic gadofullerene {Gd@C60[C(COOH)2](10)} is an attractive candidate for ex vivo labeling and noninvasive in vivo tracking of any mammalian cell via magnetic resonance imaging.