Comparative study using spheres, rods and spindle-shaped nanoplatelets on dispersion stability, dissolution and toxicity of CuO nanomaterials

Copper oxide nanoparticles with different shapes were used to examine the effect of shape on the various physicochemical properties (reactivity, aggregation, suspension stability) and to examine the behaviour by which CuO nanoparticles exhibit their biological response towards alveolar type-I cells. The different shapes examined in this study include spherical-, rod- and spindle-shaped platelet particles. In vitro dissolution studies (7 days) in 1 mM NaNO3 matrix showed a marked difference in dissolved Cu release between the nanoparticles. However, in serum-free cell-culture media (exposure media to cells), the particles' dissolution was found to be significantly enhanced with close to complete dissolution reported for all particle types. Biological studies showed both shape and size of the CuO nanoparticles tested to have a significant effect on TT-1 cell viability and release of pro-inflammatory cytokines IL-6 and IL-8. This study shows a complex interplay between particulate and dissolved species triggering the biological response. Upon immediate exposure of CuO nanoparticles of different shapes, the particulate form contributes towards the toxicity. However, for any biological response observed over and beyond a period of 24 h, the dissolved fraction becomes significant.