Chitosan-coated cerium oxide nanoparticles: enhanced antioxidant activity with increased hemolytic activity

Cerium oxide nanoparticles (CeO₂ NPs) have attracted considerable interest because of their redox-related antioxidant properties, while surface modification with chitosan may alter their physicochemical and biological behavior. However, the balance between antioxidant activity and hemocompatibility following chitosan association remains insufficiently characterized. In this study, CeO₂ NPs were synthesized using a chemical precipitation method and subsequently associated with chitosan. The physicochemical characteristics of the synthesized CeO₂ NPs were evaluated using transmission electron microscopy (TEM), atomic force microscopy (AFM), UV-visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and zeta-potential analysis. The antioxidant activity of bare CeO₂ and chitosan-associated CeO₂ (CS-CeO₂) NPs was comparatively evaluated at concentrations of 62.5-1000 µg/mL using free-radical scavenging assays. Hemolytic activity was assessed using human erythrocytes over the same concentration range. The synthesized CeO₂ NPs exhibited heterogeneous particle-size distributions, with TEM-observed particle sizes ranging from approximately 52 to 450 nm and an AFM-derived mean diameter of 64.71 nm. The CeO₂ NPs showed a positive zeta potential of + 13.5 mV. CS-CeO₂ NPs generally exhibited higher antioxidant activity than bare CeO₂ NPs, although statistically significant differences were observed only at selected concentrations. The antioxidant activity of CS-CeO₂ NPs ranged from 6.1 ± 1.2% to 36.9 ± 1.2% and increased with increasing concentration. In contrast, hemolysis also increased in a concentration-dependent manner, with CS-CeO₂ NPs producing greater hemolytic responses than bare CeO₂ NPs. Hemolysis of CS-CeO₂ NPs ranged from 3.0 ± 0.6% to 11.8 ± 1.3%, with values exceeding 5% at 500 and 1000 µg/mL. Under the conditions tested, chitosan-associated CeO₂ NPs demonstrated a potential trade-off between antioxidant activity and hemocompatibility, showing higher antioxidant activity but also greater concentration-dependent hemolysis than bare CeO₂ NPs. However, the chitosan-associated nanoparticles were not subjected to direct surface-specific characterization; therefore, the mechanisms responsible for the observed differences cannot be conclusively established. Additional studies using direct surface characterization, cellular models, and in vivo assessments are required to determine the safety, mechanism, and biomedical applicability of CS-CeO₂ NPs.

This image explains the synthesis and analysis of cerium oxide nanoparticles (CeO2 NPs) coated with chitosan (CS). The synthesis involves chemical precipitation of Ce3+ solution to form CeO2 NPs, which are then coated with chitosan, resulting in positively charged CS-CeO2 NPs.Physicochemical characterization includes:- Atomic force microscopy showing an average nanoparticle diameter of 64.71 nanometers.- UV-Vis absorption spectrum with peaks at 210 nanometers and between 300 to 350 nanometers.- FTIR spectrum confirming the presence of Ce-O bonds.- Zeta potential measurement indicating a positive charge of plus 13.5 millivolts.- Transmission electron microscopy showing the morphology of nanoparticles around 100 nanometers in size.Functional assays compare antioxidant activity and hemolysis effects between CS-CeO2 NPs and uncoated CeO2 NPs:- Antioxidant activity measured by DPPH radical scavenging increases with concentration for both, with CS-CeO2 NPs showing significantly higher activity at all concentrations up to 500 micrograms per milliliter.- Hemolysis assay on human red blood cells shows that CS-CeO2 NPs induce more hemolysis than uncoated CeO2 NPs across all tested concentrations, with hemolysis percentage rising up to nearly 90 percent at the highest concentration.Overall, the image presents the synthesis, characterization, and comparative biological activities of chitosan-coated versus uncoated cerium oxide nanoparticles. Graphic abstract (GA) Fig 1.

The online version contains supplementary material available at https://doi.org/10.1007/s10616-026-01099-0.