Effects of serum proteins on intracellular uptake and cytotoxicity of carbon nanoparticles

To explore the effects of the novel properties of carbon nanoparticles (CNPs) on cytotoxicity, the adsorption of serum proteins in cell culture medium on multi-walled carbon nanotubes and three kinds of carbon blacks was investigated. The uptake of CNPs by Hela cells was measured quantitatively using 99mTc radionuclide labeling and tracing techniques, and the dependence of CNPs uptake on serum proteins was examined. The cytotoxicity of CNPs in medium with and without serum was assayed by the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] method. It was found that cellular uptake was much higher in cells exposed to CNPs in serum-free culture medium than those in culture medium with serum. Serum proteins adsorbed on CNPs attenuated the inherent cytotoxicity of CNPs, and the extent of toxicity attenuation increased with increasing amounts of serum proteins adsorbed on CNPs. The possible reasons responsible for the considerable influence of serum proteins on cytotoxicity were indicated.