The crucial role of intrinsic properties in determining the biological effects of CeO2 nanocrystals

Nano ceria (nano-CeO 2 ) has been widely applied in various fields of industry and daily life, however, knowledge regarding the biological effects of nano-CeO 2 with different intrinsic physicochemical properties remains limited. In this study, we investigated the impact of nano-CeO 2 with different properties on the growth of a typical environmental species (romaine lettuce, Lactuca sativa L.) by exposing the plant to four types of CeO 2 (rod-like nano-CeO 2 (RNC), cubic nano-CeO 2 (CNC), spherical nano-CeO 2 (SNC) and commercial irregular CeO 2 (CIC)) during the germination stage. The results indicated that different types of CeO 2 exhibited varying inhibitory effects on plant growth. RNC and SNC significantly inhibited the elongation of roots and shoots, while CNC and CIC did not have a significant impact. We further examined the distribution and biotransformation of the four CeO 2 in plant tissues using transmission electron microscopy (TEM) and synchrotron X-ray absorption near edge structure (XANES). Specifically, the positively charged RNC and SNC were more readily adsorbed onto the root surface, and needle-like nanoclusters were deposited in the intercellular space inside the roots. The absolute content of Ce(III) in the roots romaine lettuce was in the order of RNC > SNC >> CNC >> CIC. The size and shape (i.e., exposed crystal surface) of the materials affected their reactivity and dissolution ratios, and zeta potentials affected their bioavailability, both of which influenced the overall contents of Ce 3+ ions in plant tissues. Thus, these characteristics together led to different biological effects. These findings highlight the importance of considering the intrinsic properties of nano-CeO 2 when assessing their environmental and biological effects. • The impact of four types of nano-CeO 2 on the growth of typical environmental species was studied. • RNC and SNC inhibited the plant growth, while CNC and CIC had no significant effect. • RNC and SNC showed higher adsorption and biotransformation in the roots. • Size, shape and surface chemistry of nano-CeO 2 together affect its biological effects.