Microneedle-based precision payload delivery in plants

Traditional crop delivery methods, such as foliar spray and soil application, face significant limitations, including nutrient loss, environmental impacts, and low delivery efficiency. Recent advances in nanomaterials have offered novel molecular delivery platforms, but challenges such as synthesis complexity, long-term stability, and compliance with rigorous biosafety regulations persist. To provide a simpler, lower-cost, and safer alternative, we developed a polyvinyl alcohol (PVA)-based microneedle (MN) delivery system that can be precisely applied to various plant tissues (e.g., stem, lateral branch, or petiole), which demonstrates high delivery efficiency compared to the conventional methods (3.5x higher tissue accumulation) while reducing application dose (>90% less). This MN system facilitates the delivery of diverse small molecules, ranging from fluorescent dyes, growth promoters, to antiviral hormones, into plant tissues, on the other hand showing limited wounding stress to the plant. By applying fluorescent dye-loaded MNs onto tomato stems, we demonstrated effective molecular diffusion through vascular tissues. Additionally, MNs loaded with gibberellic acid (GA3) enhanced stem and branch growth in tomatoes and restored the lateral flowering phenotype in Arabidopsis ft-10 mutants, with significant upregulation of GA receptor gene expression. Lastly, salicylic acid (SA) injections with MNs induced resistance to tomato spotted wilt virus (TSWV) in Nicotiana benthamiana , comparable to conventional spray and infiltration-based approaches. This easily fabricated and cost-effective MN system offers a promising tool for precision agriculture, enhancing plant health and productivity while significantly reducing the use of agrochemicals.