Rice husk-derived lignin-coated mesoporous silica nanoparticles for fungicide delivery: Enhancing leaf adhesion/distribution and translocation of prochloraz in plants

In this study, an innovative and sustainable nanocarrier system that was made of rice husk-derived lignin and biosilica was developed for smart delivery of prochloraz (Pro), a widely used fungicide. Mesoporous silica nanoparticles (MSNPs) were first synthesized from rice husk ash using hexadecyltrimethylammonium bromide (CTAB) as the structural agent through an acid precipitation method. The resulting MSNPs were further functionalized with amino groups (MSNPs-NH₂) to enhance the loading of Pro onto the nanocarrier, likely due to a combination of hydrogen bonds, π–π interactions, and electrostatic interactions (Pro@MSNPs-NH₂). Lignin, recovered after an acid-catalyzed organosolv pretreatment of rice husk, was coated to Pro@MSNPs-NH₂ (Pro@MSNPs-NH₂-lignin). The rice husk-derived nanocarrier system was evaluated in terms of its capacity to distribute, adhere to, and translocate within model plants (cotton, soybean, and tomato) as well as its efficacy against Fusarium oxysporum. The results revealed that lignin coating imparted hydrophobicity to hydrophilic MSNPs-NH₂, enhancing their foliar distribution and adherence as well as washout resistance onto hydrophobic plant leaves. Moreover, translocation of Pro was improved because of the nano-scale size of MSNPs, overcoming the challenges in poor absorption by plant leaves. Bioactivity trial results showed that the Pro@MSNPs-NH₂-lignin delivery system exhibited effective fungicidal performance, which led to 80.5% of fungal growth inhibition at 0.125 mg Pro/mL on Day 4, comparable to 75.0% of growth inhibition with the use of pure prochloraz at the same loading. Overall, this study demonstrated the significant potential of rice husk-derived sustainable nanocarriers for efficient delivery of agrochemicals, supporting the development of sustainable and resilient agriculture.