Influence of copper oxide nanoparticle shape on bioaccumulation, cellular internalization and effects in the estuarine sediment-dwelling polychaete, Nereis diversicolor

CuO nanoparticles (NPs) released into the aquatic environment will likely accumulate in the sediment. Here we synthesized and characterized CuO NPs with different shapes and thus sizes: spheres, rods and spindles. Nereis diversicolor were exposed for 10 days to control sediment or sediment spiked with CuO NPs or aqueous Cu (Cu-Aq, CuCl₂) at 7, 70 and 140 μg Cu g^-1 dw sediment. Cu from all Cu treatments accumulated in worms in a concentration-dependent manner. Only Cu-Aq decreased burrowing, suggesting that worms avoid Cu when added to sediment as Cu-Aq, but not CuO NPs. Transmission Electron Microscopy of gut sections indicated limited presence of CuO NP-like objects in the gut lumen, but evidence on whether accumulated Cu from CuO NP exposure was internalized as particles was not conclusive. Overall, bioavailability and avoidance was not influenced by particle shape or size, whereas Cu form (Cu-Aq vs particulate) and exposure concentration had significant impact.