A plug-and-play strategy for agrochemical delivery using a plant virus nanotechnology

Abstract Delivery of agrochemicals into soil presents a challenge, as the active ingredients are often hydrophobic and do not possess adequate soil mobility to reach their target pest. Previously, plant virus nanoparticles have been shown to penetrate soil and deliver agrochemicals for the treatment of plant parasitic nematodes. For example, tobacco mild green mosaic virus (TMGMV) can be functionalized with agrochemicals through bioconjugation, infusion at the coat protein interface, or encapsulation through thermal shapeshifting (rod-to-sphere). There continues to be a need to expand approaches for agrochemical display and delivery with a need for plug-and-play technology to be applicable for multiple nanoparticle platforms and agrochemicals. Toward this goal, we turned toward a bio-specific coupling strategy making use of the biotin-(strept)avidin system. Herein, we conjugated TMGMV with either avidin or biotin using azide-alkyne cycloaddition. The avidin/biotin-functionalized TMGMV nanoparticles were then characterized by gel electrophoresis and electron microscopy to confirm cargo loading and the nanoparticle’s structural integrity. Soil column assays confirmed that soil mobility was maintained upon chemical modification. Ivermectin modified with biotin or streptavidin linkers was then introduced to the TMGMV-avidin/biotin nanoparticles and binding propensity and loading were validated by QCM-D and a competitive ELISA. Finally, the ivermectin-loaded TMGMV nanoparticles were used to treat C. elegans in a gel burrowing assay, demonstrating that either pesticide loading strategy resulted in active TMGMV nanoparticle formulation that significantly reduced the mobility of nematodes, even after passing through soil. In stark contrast, free ivermectin only exhibited efficacy when applied directly to nematodes; the free pesticide was lost in the soil column—highlighting the need for a delivery system. The presented approach provides a facile plug-and-play approach for pesticide loading onto TMGMV nanoparticles. In particular, biotinylated TMGMV with streptavidin-conjugated ivermectin served as the most effective formulation. Importantly this method does not require heat, which contrasts our previous method of thermal reshaping that requires sample and pesticide exposure to temperatures > 96 °C. We envision the bio-specific loading strategy could be extended to other protein or inorganic nanoparticles to advance soil treatment strategies.