PVA-based microneedle systems for precise molecular 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 enabled novel molecular delivery platforms; however, 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-based microneedle (MN) delivery system that can be precisely applied to various plant tissues, including stems, lateral branches, or petioles. This system demonstrates high delivery efficiency compared with conventional methods (3.5× higher tissue accumulation) while reducing the application dose (>90% reduction). It facilitates the delivery of diverse small molecules, ranging from fluorescent dyes to growth promoters and antiviral hormones, into plant tissues while causing minimal wounding stress. In particular, salicylic acid injection using MNs induced resistance to tomato spotted wilt virus in Nicotiana benthamiana, opening a new possibility for plant immunity engineering without gene editing. Overall, 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.