On shape dependence of the toxicity of rutile nanoparticles

Using DFT treatment based on the B3LYP hybrid functional, the nearly spherical structure of [Ti₇O₂₈H₂₆]²⁻, the rod-like structures of [Ti₂O₁₀H₁₀]²⁻, and [Ti₇O₃₀H₁₀]²⁻ chains in singlet ground spin states and the structures of their neutral complexes with Cu²⁺ ions coordinated at various terminal or bridging oxygen sites in doublet ground spin states are optimized in order to assess the toxicity of rutile nanoparticles of various shapes. For this purpose Cu-ligand interaction energy parameters and Cu charges in the above systems under study are evaluated. Spherical structures are more reactive than the rod-like chains of the (nearly) same size. The reverse relation holds for the degree of their toxicity as indicated by the extent of the electron density transfer to a Cu²⁺ probe. The experimentally observed higher cytotoxicity of the rod-like nanoparticles in comparison with the spherical ones might be explained by the higher electron density transfer to the interacting cells.