A Flexible, Digital Light Processing (DLP) 3D Printed and Coated Microneedle Array (CμNA) for Precision Delivery of Novel Nanotherapeutics to Plant Tissue

This work reports on the design, fabrication, and characterization of a flexible digital light processing (DLP) 3D-printed and coated microneedle patch, which is utilized in transporting copper-based novel nanotherapeutics to the stem tissue of Huanglongbing (HLB)-affected trees. HLB has decimated the previously robust a nd profitable citrus industry in the state of Florida and is caused by a phloem -limited bacterium "Candidatus Liberibacter asiaticus" (CLas). Any treatment for HLB must be precision delivered to phloem tissue, demanding an innovative delivery mechanism that is user friendly and can bridge the gap between the lab and the grove. It is hypothesized that a coated microneedle array (cμNA) will efficiently create penetrations into the stem tissue by which treatments can reach the underlying thin phloem tissue. Based on multiple therapeutic selection criteria, metallic copper was selected and used for this study. Copper is formulated in a way that follows sustained release kinetics and can travel through the plant vascular system without causing phytotoxicity. The microneedles were designed to have an optimized surface area for maximizing the uptake of the formulated copper coating. These microneedles were subsequently characterized in a series of in vitro water studies that shows the sustained release of copper over time.