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A new environmentally friendly method produces cerium oxide nanodots with antioxidant, antimicrobial, and anticancer activity through the use of debranched starch derived from Curcuma longa.
Study: Curcuma longa debranched starch assisted synthesis of cerium oxide nanoparticles and its antioxidant, anticancer, antimicrobial, and anti-biofilm activities. Image Credit:ultramansk/Shutterstock.com
The work, published in Scientific Reports, demonstrates how plant-based materials can be harnessed to create highly functional nanomaterials while reducing reliance on harsh chemicals and energy-intensive processes.
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Nanoparticles are increasingly used in medicine, catalysis, and environmental applications, but many conventional synthesis methods rely on high temperatures, toxic solvents, and complex processing steps.
Green synthesis approaches aim to reduce these drawbacks by using biodegradable, renewable materials that can act as both reducing and stabilizing agents.
Cerium oxide nanoparticles (CeO2NPs), also known as nanoceria, are of particular interest because their biological activity depends strongly on particle size, surface chemistry, and oxidation state.
Previous studies have shown that green-synthesized nanoceria can exhibit selective toxicity toward cancer cells while sparing healthy cells, motivating efforts to develop safer and more controllable production routes.
The First Use of Debranched Curcuma longa Starch
In this study, researchers report for the first time the use of debranched Curcuma longa starch to synthesize cerium oxide nanodots via a sol-gel-based green approach. Debranched starch plays multiple roles: it reduces cerium ions, stabilizes growing nanoparticles, and prevents aggregation during synthesis.
This strategy produced well-dispersed, spherical cerium oxide nanodots with a narrow size distribution of 2-4 nm, dimensions that are difficult to achieve consistently using traditional chemical routes.
Careful Characterization of the Nanodots
The researchers used a comprehensive set of analytical techniques to confirm nanoparticle formation and structure. UV/Vis spectroscopy revealed characteristic absorption features associated with cerium oxide nanostructures, reported between 315 nm and approximately 350 nm across different sections of the study.
Fourier transform infrared spectroscopy (FTIR) identified chemical interactions between cerium oxide and starch-derived functional groups, while X-ray diffraction (XRD) confirmed the crystalline, cubic fluorite structure of CeO2.
High-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) showed uniformly spherical nanodots in the 2-4 nm range. X-ray photoelectron spectroscopy (XPS) demonstrated the coexistence of Ce3+ and Ce4+ oxidation states, along with oxygen vacancies, features known to drive nanoceria’s redox activity.
Biological testing showed that the cerium oxide nanodots possess strong antioxidant activity. In standard radical scavenging assays, the nanoparticles exhibited IC50 values of 3.2 ± 0.23 µg/mL for DPPH and 3.66 ± 0.18 µg/mL for ABTS, outperforming common antioxidant references.
This activity is linked to reversible cycling between Ce3+ and Ce4+ ions on the nanoparticle surface. The authors emphasize that this redox behavior is context-dependent: cerium oxide nanoparticles can act as antioxidants or pro-oxidants depending on their environment, concentration, and biological target.
Antibacterial and Anti-Biofilm Effects
The nanodots also demonstrated antibacterial activity against a range of clinically relevant pathogens, including Corynebacterium diphtheriae, Escherichia coli, Klebsiella pneumoniae, and Salmonella typhi.
More notably, anti-biofilm activity was observed primarily against E. coli and C. diphtheriae, organisms known for forming persistent biofilms that resist conventional antibiotics. Microscopy and mechanistic analysis suggest that reactive oxygen species generation and membrane disruption play key roles in this effect.
To explore anticancer potential, the researchers evaluated cytotoxicity against HepG2 human hepatocellular carcinoma cells using the MTT assay. The cerium oxide nanodots showed a clear dose-dependent response, with an IC50 of 178 ± 14 µg/mL.
The proposed mechanism involves modulation of oxidative stress, mitochondrial dysfunction, and activation of apoptotic pathways. While prior studies suggest that nanoceria may preferentially affect cancer cells over normal cells, the authors note that this selectivity was not directly tested here.
Encouraging Safety Signals with Clear Limits
Beyond efficacy, the study also examined hemocompatibility. Red blood cell hemolysis assays showed that the nanodots reduced membrane damage caused by disruptive agents, indicating favorable blood compatibility.
However, the authors are careful to stress that all findings are based on in vitro experiments. Further mechanistic studies, in vivo testing, and long-term safety assessments will be required before biomedical or clinical applications can be considered.
By combining plant-derived starch chemistry with cerium oxide nanotechnology, the work highlights a viable path toward more sustainable nanoparticle synthesis without sacrificing functionality. The results reinforce the idea that green synthesis methods can produce nanomaterials with precise size control, rich surface chemistry, and broad biological activity.
The study offers both a new synthesis strategy and a reminder that sustainability and performance need not be at odds.
Journal Reference
Sana S.S. et al. (2026). Curcuma longa debranched starch-assisted synthesis of cerium oxide nanoparticles and their antioxidant, anticancer, antimicrobial, and anti-biofilm activities. Scientific Reports (2026). DOI: 10.1038/s41598-026-35249-3, https://www.nature.com/articles/s41598-026-35249-3