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

Dispersion stability of nanoparticles of C-60 under a model condition simulating a physiological environment was studied by dynamic light scattering. Although the C-60 nanoparticles at a concentration of 9.3 x 10(-6) M (6.7 mu g/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 C-60 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 C-60 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 C-60 nanoparticles in which no such effect has been considered.