Antioxidant colloids via heteroaggregation of cerium oxide nanoparticles and latex beads

Antioxidant colloids were developed via controlled heteroaggregation of cerium oxide nanoparticles (CeO₂ NPs) and sulfate-functionalized polystyrene latex (SL) beads. Positively charged CeO₂ NPs were directly immobilized onto SL particles of opposite surface charge via electrostatic attraction (SL/Ce composite), while negatively charged CeO₂ NPs were initially functionalized with poly(diallyldimethylammonium chloride) (PDADMAC) polyelectrolyte and then, aggregated with the SL particles (SPCe composite). The PDADMAC served to induce a charge reversal on CeO₂ NPs, while the SL support prevented nanoparticle aggregation under conditions, where the dispersions of bare CeO₂ NPs were unstable. Both SL/Ce and SPCe showed enhanced radical scavenging activity compared to bare CeO₂ NPs and were found to mimic peroxidase enzymes. The results demonstrate that SL beads are suitable supports to formulate CeO₂ particles and to achieve remarkable dispersion storage stability. The PDADMAC functionalization and immobilization of CeO₂ NPs neither compromised the peroxidase-like activity nor the radical scavenging potential. The obtained SL/Ce and SPCe artificial enzymes are foreseen to be excellent antioxidant agents in various applications in the biomedical, food, and cosmetic industries.