Determination of equilibrium constant of C₆₀ fullerene binding with drug molecules

We report a new analytical method that allows the determination of the magnitude of the equilibrium constant of complexation, K_h, of small molecules to C₆₀ fullerene in aqueous solution. The developed method is based on the up-scaled model of C₆₀ fullerene-ligand complexation and contains the full set of equations needed to fit titration datasets arising from different experimental methods (UV-Vis spectroscopy, ¹H NMR spectroscopy, diffusion ordered NMR spectroscopy, DLS). The up-scaled model takes into consideration the specificity of C₆₀ fullerene aggregation in aqueous solution and allows the highly dispersed nature of C₆₀ fullerene cluster distribution to be accounted for. It also takes into consideration the complexity of fullerene-ligand dynamic equilibrium in solution, formed by various types of self- and hetero-complexes. These features make the suggested method superior to standard Langmuir-type analysis, the approach used to date for obtaining quantitative information on ligand binding with different nanoparticles.