Computer-Aided Design of Nanoceria Structures as Enzyme Mimetic Agents: The Role of Bodily Electrolytes on Maximising Their Activity

Nanoceria, typically used for ‘clean air’ catalytic converter technologies, is the same material that could also be used as a nanomedicine. Specifically, nanoceria, which can capture, store and release oxygen, for oxidative/reductive reactions, can also be used to control oxygen content in cellular environments; as a ‘nanozyme’, nanoceria mimics enzymes by acting as an antioxidant agent. The computational design procedures for predicting active materials for catalytic converters can therefore be used to design active ceria nanozymes. Crucially, the ceria nanomedicine is not a molecule; rather it is a crystal and exploits its unique crystal properties.

Here, we use ab initio and classical computer modelling, together with experiment, to design structures for nanoceria that maximises its nanozymetic activity. We predict that the nanomaterial should have (truncated) polyhedral or cuboidal morphologies to expose (active) CeO2 {100} surfaces. It should also contain oxygen vacancies and surface –OH species. We also show that the surface structures strongly affects the biological activity of nanoceria. Analogous to catalyst poisoning, phosphorus 'poisoning' - the interaction of nanoceria with phosphate, a common bodily electrolyte – emanates from phosphate ions binding strongly to CeO2{100} surfaces, inhibiting oxygen capture and release and hence its ability to act as an nanozyme. Conversely, phosphate interaction with {111} surfaces is weak and therefore these surfaces protect the nanozyme against poisoning.

The atom-level understanding presented here also illuminates catalytic processes and poisoning in ‘clean-air’ or fuel-cell technologies because the mechanism underpinning and exploited in each technology – oxygen capture, storage and release – is identical.