Subcellular Distribution of Polyhydroxylated Metallofullerene Gd@C₈₂(OH)₂₂ in Different Tissues of Tumor-Bearing Mice

Endohedral metallofullerenes have unique chemical and physical properties that are essential for biomedical applications. They can be used as a radiotracer in magnetic resonance and X-ray imaging (MRI and XRI). Polyhydroxylated metallofullerene Gd@C₈₂(OH)_x has been studied as a new high efficient contrast agents for MRI and has also shown high efficiency for antitumor growth. Previous studies have shown that Gd@C₈₂(OH)₂₂ mainly accumulated in bone, pancreas, liver and kidney after intraperitoneal administration. However, whether the nanoparticles can enter into cells and the site of their potential action remains unclear. In this work, the distribution patterns of Gd@C₈₂(OH)₂₂ in subcellular compartments were studied using the techniques of differential centrifugation and ICP-MS analysis. The results indicate that the Gd@C₈₂(OH)₂₂ can enter into cells and the subcellular distribution patterns are significantly different from that of GdCl₃. GdCl₃ has much higher bioavailability for mice than Gd@C₈₂(OH)₂₂. Therefore, the present data suggest that Gd@C₈₂(OH)₂₂ in living systems may be not decomposed to release free Gd³⁺ ion and may be metabolized as a pristine carbon cage.