The Crucial Role of Intrinsic Properties in Determining the Biological Effects of Ceo2 Nanocrystals

Abstract

Nano ceria (nano-CeO2) has been widely applied in various fields of industry and daily life, however, knowledge regarding the biological effects of nano-CeO2 with different intrinsic physicochemical properties remains limited. In this study, we investigated the impact of nano-CeO2 with different properties (shape, size, surface charge, etc.) on the growth of a typical environmental species (romaine lettuce, Lactuca sativa L.) by exposing the plant to four types of CeO2 (rod-like nano-CeO2 (RNC), cubic nano-CeO2 (CNC), spherical nano-CeO2 (SNC) and bulk CeO2 (BC)) during the germination stage. The results showed that different types of CeO2 exhibited distinct inhibitory effects on plant growth, with root and shoot elongation decreasing by 19.2%/24.9% under RNC treatment and by 32.2%/27.3% under SNC treatment, while CNC and BC showed no significant effects. We further examined the distribution and biotransformation of the four types of CeO2 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. Additionally, the absolute contents of Ce(III) in the roots of the RNC, SNC and CNC groups were calculated to be 7988.8, 5297.7, and 961.9 mg/kg, respectively, while BC showed minimal transformation within the romaine lettuce roots. The size and shape (i.e., exposed crystal surface) of the materials affected their reactivity and dissolution ratios, and surface charge affected their bioavailability, both of which influenced the overall contents of Ce3+ 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-CeO2 when assessing their environmental and biological effects.

Keywords: nano-CeO2, biological effects, intrinsic properties, biotransformation, bioavailability