(650f) Understanding and Controlling the Plant Antifungal Activity of New Classes of Environmentally Benign Nanoparticles

Our group has introduced a class of environmentally benign nanoparticles (EbNPs) for biotechnology (Nature Nanotechn. 10:817, 2015). These nanoparticles made of lignin can biodegrade after use, with low potential for nanotoxic impact. We use a semi-continuous synthesis system to produce large amounts of EbNPs by a non-LaMerian mechanism, and we investigate these nanoparticles as delivery vehicles of actives to biological surfaces. These EbNPs have already been proven to be efficient antibacterial agents when loaded with silver ions and coated with polyelectrolyte. We are now using the biopolymer chitosan as a nanocoating, allowing us to control the surface charge of the EbNPs. The charge due to chitosan enables the EbNPs to adhere to plants, which usually have an intrinsic negative charge. We evaluate the ability of uncoated and coated EbNPs to prevent damage from the fungus Botrytis to roses compared to the industry standard chemical fludioxonil. While chitosan coated nanoparticles have improved adherence to petals, the uncoated EbNPs prevent fungal growth more efficiently. The lignin nanoparticles appear to protect the petals by disrupting the interaction between them and spores, and by adhering to spores, impeding their development and causing aggregation. Using brightfield, fluorescence, and scanning electron microscopy, we study the fundamental interactions between spores, EbNPs, and rose petals to understand the origins of the antifungal activity of the lignin nanoparticles. We observe the effects of EbNP treatment before and after the inoculation of rose petals with spores to understand how the timing and physical characteristics of lignin nanoparticles and spores impact growth and development of germ tubes and hyphae. We will report our conclusions about the correlation of the colloidal interactions, “coffee ring” formation, and infectivity to rose petals. By understanding these interactions, one can formulate novel, efficient, and environmentally benign antifungal products.