Selenium-doped nanoparticles improve fungicide retention, activate plant defenses, and lower toxicity in environmentally safer pesticide formulations.
(Nanowerk Spotlight) Chemical pesticide use is a cornerstone of industrial agriculture, yet most formulations suffer from poor delivery efficiency and unintended ecological consequences. Less than 1% of applied pesticide typically reaches its target, with the remainder lost to drift, runoff, or degradation. This not only drives up input costs but also contributes to widespread environmental contamination and harm to non-target organisms.
Among the challenges in pesticide application are poor leaf adhesion, susceptibility to rain erosion, and limited bioavailability. Improving these properties without increasing ecological risk has been a persistent problem in crop protection chemistry.
Oil-in-water emulsions have gained traction as delivery systems for hydrophobic pesticides, offering better distribution and wettability. However, traditional emulsions often rely on synthetic surfactants and solvents that pose toxicity and degradation issues. In response, Pickering emulsions—stabilized by solid particles rather than surfactants—have emerged as a promising alternative. By using biodegradable particles as stabilizers, these systems can improve emulsion stability while reducing the environmental load of synthetic additives. Materials such as silica, cellulose, and lignin have all been explored for this purpose, but their function is often limited to physical stabilization.
Another largely untapped opportunity is the integration of immune-activating agents into pesticide formulations. Plants naturally deploy complex defense mechanisms regulated by hormones like jasmonic acid and salicylic acid. These internal systems are rarely leveraged in modern crop protection products. Selenium, a trace element essential to both plant and animal physiology, has been shown to enhance plant resistance to environmental stress and disease by modulating antioxidant activity and hormone signaling. However, practical delivery of selenium in a bioavailable and stable form remains a challenge.
A new study published in Advanced Functional Materials (“Selenium‐Doped Biomass‐Based Nanoparticles Drive Agricultural Emulsions toward a Novel “Offense‐Defense Integration” Strategy”) addresses both these needs by engineering a selenium-doped nanoparticle-based Pickering emulsion for agricultural use. Researchers from China Agricultural University developed a formulation in which prochloraz, a common antifungal agent, is emulsified using zein-based nanoparticles doped with selenium. Zein is a biodegradable protein derived from corn byproducts, and in this context serves as both a stabilizing matrix and a delivery vehicle for selenium.
Comprehensive characterization and formation mechanism of Zein-Se NPs and Pro-Pickering emulsions. A) Schematic illustration of the Zein-Se NPs preparation. B) Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the Zein-Se NPs. C) EDS, D) appearance morphology, E) element content, F) DLS, and G) XPS of the Zein-Se NPs. H) XRD, I) FT-IR, and J) TGA of the samples. K) Schematic illustration of the Pro-Pickering preparation process and possible interfacial bonding mechanism of the Zein-Se NPs. (Image: Reprinted with permission by Wiley-VCH Verlag) (click on image to enlarge)
The nanoparticles were synthesized by reducing sodium selenite with ascorbic acid in the presence of zein, forming core-shell structures with embedded selenium. These particles had an average diameter of 124 nanometers and exhibited uniform morphology. Their presence at the oil-water interface enabled the formation of stable emulsions with improved droplet integrity. A 5:95 oil-to-water ratio was found to produce the most stable formulation, with emulsion droplets averaging 4.4 micrometers in size.
Compared to a commercial prochloraz emulsifiable concentrate (Pro-EC), the selenium-doped Pickering emulsion (Pro-Pickering) showed enhanced interfacial behavior. It exhibited significantly lower surface tension and contact angle on cucumber leaves, leading to better spreading and retention. Under simulated rainfall, Pro-Pickering retained 27% more active ingredient than the commercial formulation. Microscopy confirmed stronger adhesion of droplets to leaf surfaces, aided by hydrogen bonding and hydrophobic interactions between the nanoparticles and the waxy cuticle of the leaves.
Biological efficacy was evaluated against *Botrytis cinerea*, a fungal pathogen known for infecting a broad range of crops. In vitro, both formulations showed comparable fungicidal activity. However, in live plant assays, Pro-Pickering reduced disease incidence by nearly 49% more than Pro-EC at equivalent dosages. This enhanced protection was accompanied by a measurable decrease in reactive oxygen species and lipid peroxidation, as well as increased activity of defense-related enzymes such as superoxide dismutase, peroxidase, and polyphenol oxidase.
To probe the underlying mechanisms, the researchers conducted transcriptomic and metabolomic analyses. These revealed that Pro-Pickering treatment upregulated genes involved in jasmonic acid signaling, amino acid metabolism, and glutathione-mediated oxidative stress response. Metabolite profiling supported these findings, showing elevated levels of defense-related compounds including lignin precursors and flavonoids.
The activation of α-linolenic acid metabolism suggested enhanced biosynthesis of jasmonic acid and related oxylipins, which coordinate systemic immune responses. Furthermore, genes associated with photosynthetic efficiency were also upregulated, suggesting that the formulation mitigated pathogen-induced damage to chloroplasts.
Toxicological and environmental assessments indicated that Pro-Pickering had a more favorable safety profile than Pro-EC. In mouse models, selenium and prochloraz were present at low levels in major organs, with the highest selenium concentration in the liver still within a physiologically acceptable range.
Human liver cell assays showed minimal cytotoxicity, and in some cases, selenium nanoparticles appeared to promote cell growth after extended exposure. Soil microbiome analysis showed that Pro-EC disrupted bacterial diversity, while Pro-Pickering had negligible impact. Aquatic toxicity tests using zebrafish embryos confirmed lower mortality and malformation rates for Pro-Pickering compared to the commercial formulation.
By combining improved physical delivery with biochemical activation of plant defenses, the selenium-doped Pickering emulsion offers a multifunctional approach to crop protection. It replaces synthetic surfactants with biodegradable stabilizers and adds a layer of immune stimulation to conventional fungicidal action. The result is a formulation that not only performs better in field-relevant conditions but also minimizes ecological disruption.
While further field trials and regulatory evaluation are needed, this work provides a technically grounded pathway toward more integrated and environmentally responsible pesticide design.
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