Authors: Pierluigi Lasala | Tiziana Latronico | Umberto Mattia | Rosa Maria Matteucci | Antonella Milella | Matteo Grattieri | Grazia Maria Liuzzi | Giuseppe Petrosillo | Annamaria Panniello | Nicoletta Depalo | Maria Lucia Curri | Elisabetta Fanizza
Source: Antioxidants (article, 2025-07-25)
Field: Materials Science — Materials Chemistry

Enhancing Antioxidants Performance of Ceria Nanoparticles in Biological Environment via Surface Engineering with o-Quinone Functionalities The development of ceria (CeO<sub>2-x</sub>)-based nanoantioxidants requires fine-tuning of structural and surface properties for enhancing antioxidant behavior in biological environments. In this contest, here ultrasmall water-dispersible CeO<sub>2-x</sub> nanoparticles (NPs), characterized by a high Ce<sup>3+</sup>/Ce<sup>4+</sup> ratio, were synthesized in a non-polar solvent and phase-transfer to an aqueous environment through ligand-exchange reactions using citric acid (CeO<sub>2-x</sub>@Cit) and post-treatment with dopamine hydrochloride (CeO<sub>2-x</sub>@Dopa). The concept behind this work is to enhance via surface engineering the intrinsic antioxidant properties of CeO<sub>2-x</sub> NPs. For this purpose, thanks to electron transfer reactions between dopamine and CeO<sub>2-x</sub>, the CeO<sub>2-x</sub>@Dopa was obtained, characterized by increased surface Ce<sup>3+</sup> sites and surface functionalized with polydopamine bearing <i>o</i>-quinone structures as demonstrated by complementary spectroscopic (UV-vis, FT-IR, and XPS) characterizations. To test the antioxidant properties of CeO<sub>2-x</sub> NPs, the scavenging activity before and after dopamine treatment against artificial radical 1,1-diphenyl-2-picrylhydrazyl (DPPH<sup>·</sup>) and the ability to reduce the reactive oxygen species in Diencephalic Immortalized Type Neural Cell line 1 were evaluated. CeO<sub>2-x</sub>@Dopa demonstrated less efficiency in DPPH<sup>·</sup> scavenging (%radical scavenging activity 13% versus 42% for CeO<sub>2-x</sub>@Cit before dopamine treatment at 33 μM DPPH<sup>·</sup> and 0.13 mg/mL loading of NPs), while it markedly reduced intracellular ROS levels (ROS production 35% compared to 66% of CeO<sub>2-x</sub>@Cit before dopamine treatment with respect to control-<i>p</i> < 0.001 and <i>p</i> < 0.01, respectively). While steric hindrance from the dopamine-derived polymer layer limited direct electron transfer from CeO<sub>2-x</sub> NP surface to DPPH<sup>·</sup>, within cells the presence of <i>o</i>-quinone groups contributed with CeO<sub>2-x</sub> NPs to break the autoxidation chain of organic substrates, enhancing the antioxidant activity. The functionalization of NPs with <i>o</i>-quinone structures represents a valuable approach to increase the inherent antioxidant properties of CeO<sub>2-x</sub> NPs, enhancing their effectiveness in biological systems by promoting additional redox pathways. Chemistry ; DPPH ; Antioxidant ; Nanoparticle ; Catechol ; Electron transfer ; Ascorbic acid ; Nuclear chemistry ; Crystallinity ; Dopamine ; Organic chemistry ; Nanotechnology ; Materials science ; Crystallography Advanced Nanomaterials in Catalysis ; Electrochemical sensors and biosensors ; Nanoparticles: synthesis and applications