Biodistribution of intravenously administered amphiphilic β-cyclodextrin nanospheres

Amphiphilic β-cyclodextrin (βCDa) nanospheres (mean diameter 90–110 nm) prepared by the solvent displacement method were developed as a colloidal drug delivery system. In order to survey the fate of these nanoparticles, the amphiphilic β-cyclodextrin was first iodinated by a two-step procedure involving iodination of the primary face followed by an acylation of the secondary face. After radiolabeling of this derivative with 125I, nanospheres made of βCDa/βCDa 125I were formulated. After a single intravenous injection of labeled nanoparticles in mice, the organ distribution was analyzed from 10 min to 6 days. A rapid clearance of 125I-labeled βCDa nanospheres from the blood circulation to the mononuclear phagocyte system was visualized by non-invasive planar imaging study. Radioactivity measurements in organs showed that the nanospheres mainly concentrated in the liver and the spleen where 28 and 24% of the radioactivity per gram of organ was, respectively, found 10 min after injection. At the opposite, the blood activity was low at that time and become negligible thereafter. Finally, the fact that no particular sign of toxicity is observed in injected animals should be emphasized since it is the first report on intravenous administration of βCDa nanoparticles.