Behavior of nanoceria in biologically-relevant environments

Cerium oxide nanoparticles (nanoceria) have gained considerable attention in biological research due to their anti-oxidant like behaviour and regenerative nature. The current literature on nanoceria reports many successful attempts on harnessing the beneficial therapeutic properties in biology. However studies have also shown toxicity with some types of nanoceria. This article discusses issues associated with the behaviours of nanoceria in biological systems and identifies key knowledge gaps. We explore how salient physico-chemical properties (size, surface chemistry, surface stabilizers) of nanoceria corresponds to its behaviour in biological relevant buffers and cell culture media, and this can provide guidelines for potential positive and negative aspects of nanoceria in biological systems. Based on variations of results reported in the literature, important issues need to be addressed. Are we really studying the same particles with slight variations in size and physico-chemical properties or do the particles being examined have fundamentally different behaviours? Are the variations observed the result of differences in the initial properties of the particles or the results of downstream effects that emerge as the particles are prepared for specific studies and they interact with biological or other environmental moieties? How should particles be appropriately prepared for relevant environmental/toxicology/safety studies? It is useful to recognize that nanoparticles encompass some of the same complexities and variability associated with biological components.