Stabilization of C60 nanoparticles by protein adsorption and its implications for toxicity studies

Dispersion stability of nanoparticles of C60 under a model condition simulating a physiological environment was studied by dynamic light scattering. Although the C60 nanoparticles at a concentration of 9.3 x 10(-6) M (6.7 microg/mL) coagulated and precipitated out rapidly in phosphate buffered saline, coagulation was suppressed completely when HSA was present at concentrations above 1 mg/mL. DLS results show that the HSA molecules adsorb onto the surfaces of the C60 nanoparticles, thereby forming a protective layer, and prevent salt-induced coagulation. DLS results also indicate that the HSA molecules take an expanded conformation on the surface. Our findings suggest that C60 nanoparticles can be stabilized in the physiological environment even if they are not deliberately stabilized by using stabilizers and are of significant implications for the on-going efforts to evaluate the cytotoxicity of C60 nanoparticles in which no such effect has been considered.