Biodistribution of 99mTc-C60(OH)x in Sprague–Dawley rats after intratracheal instillation

An increasing number of studies have been devoted to studying the respiratory toxicity of carbon nanomaterials, but little information is known, thus far, on the biodistribution of these nanomaterials after inhalation or intratracheal instillation. We synthesized and labeled a polyhydroxylated derivative of fullerene C60(OH)x (x = 22, 24) with 99mTc. With single photon emission computed tomography imaging and 〈gamma〉-ray counting techniques, the biodistribution of 99mTc-C60(OH)x in Sprague–Dawley rats after intratracheal instillation was studied. It was found that, besides the highest retention in the lung, 99mTc-C60(OH)x is distributed mainly in the liver, bone, and spleen, with no uptake found in brain. The long-term retention in the lung and the very fast clearance from the blood revealed a transient characteristic of penetrating the alveolar-capillary barrier. The dimensions and size distribution, as well as in vivo aggregation of 99mTc-C60(OH)x, may affect the capability and kinetic process of penetrating the alveolar-capillary barrier. The results provide guidance for further study of the respiratory toxicity of carbon nanomaterials.