(546b) Flash Nanoprecipitation As an Agrochemical Nanocarrier Formulation Platform: Phloem Uptake and Translocation after Foliar Administration

The increasing severity of pathogenic and environmental stressors that negatively affect plant health has led to interest in developing next-generation agrochemical delivery systems capable of precisely trafficking active agents to specific sites within plants. Many agrochemicals of interest stand to benefit from formulation into colloidal suspensions for improved wettability, flowability, and possibly uptake into plants, but the techniques used to prepare such formulations (cost, scale, etc.) must be carefully considered. In this work, we adapt Flash NanoPrecipitation (FNP), a scalable antisolvent precipitation technology driven by rapid turbulent mixing, to prepare organic core-shell nanocarriers to evaluate for uptake and translocation in tomato plants following foliar or root administration.

NCs ranging in diameter from 55nm to 200nm, with surface zeta potentials from -40mV to +40mV, and with seven different shell material properties were prepared and studied. Shell materials included synthetic polymers poly(acrylic acid), poly(ethylene glycol), and poly(2-(dimethylamino)ethyl methacrylate), naturally-occurring compounds fish gelatin and soybean lecithin, and semisynthetic hydroxypropyl methylcellulose acetate succinate (HPMCAS). NC cores contained a gadolinium tracer for tracking by mass spectrometry, a fluorescent dye for tracking by confocal microscopy, and model hydrophobic compounds (alpha tocopherol acetate, polystyrene) that could be replaced by agrochemical payloads in subsequent applications. After foliar application onto tomato plants with Silwet L-77 surfactant, internalization efficiencies up to 85% and NC translocation efficiencies up to 32% were observed. Significant NC trafficking to stem and roots suggests a high degree of phloem loading for these materials. Results were corroborated by confocal microscopy and synchrotron X-ray fluorescence mapping. NCs stabilized by cellulosic HPMCAS exhibited the highest degree of translocation, followed by formulations with significant surface charge. The results from this work indicate that an industrially-viable pharmaceutical nanoformulation process (FNP) using biocompatible materials like HPMCAS are promising agrochemical delivery vehicles, and shed light on the optimal properties of organic NCs for efficient foliar uptake, translocation, and delivery.