Preparation and biodistribution of radiolabeled fullerene C60 nanocrystals

The present study describes for the first time a procedure for the radiolabeling of fullerene (C-60) nanocrystals (nanoC(60)) with Na I-125, as well as the biodistribution of radiolabeled nanoC(60) (I-125-nanoC(60)). The solvent exchange method with tetrahydrofuran was used to make colloidal water suspensions of radiolabeled nanoC(60) particles. The radiolabeling procedure with the addition of Na I-125 to tetrahydrofuran during dissolution of C-60 gave a higher radiochemical yield of radiolabeled nanoC(60) particles in comparison to the second option, in which Na I-125 was added after C-60 was dissolved. Using photon correlation spectroscopy and transmission electron microscopy, I-125-nanoC(60) particles were found to have a crystalline structure and a mean diameter of 200-250 nm. The I-125-nanoC(60) had a particularly high affinity for human serum albumin, displaying 95% binding efficiency after 1 h. Biodistribution studies of I-125-nanoC(60) in rats indicated significant differences in tissue accumulation of I-125-nanoC(60) and the radioactive tracer Na I-125. The higher accumulation of radiolabeled nanoC(60) was observed in liver and spleen, while accumulation in thyroid, stomach, lungs and intestines was significantly lower in comparison to Na I-125. In addition to being useful for testing the biological distribution of nanoC(60), the described radiolabeling procedure might have possible applications in cancer radiotherapy.