Rhamnolipids, Nanoemulsions, and Biomimetic Membranes: A biophysical approach to sustainable crop protection

MOTTOLA, MILAGRO; KOURDOVA, LUCILLE TIHOMIROVA; FABRO, GEORGINA; FANANI, MARÍA LAURA

Córdoba

Congreso; LI Congreso Sociedad Argentina de Biofísica; 2023

Sociedad Argentina de Biofísica

Plant pathogens and pests threaten global crop yields, raising concerns about foodsecurity and the environment. Using conventional pesticides has limitations, such asresistance and environmental impact. To address these challenges, we explorebioprotectants as sustainable alternatives. Natural Rhamnolipids (RL-Nat), a class ofbiosurfactants, have emerged as promising bioprotectants capable of inducing plantresistance against diverse pathogens. Our research covers a comprehensive study of howRLs interact with complex biomimetic plant membranes and the development of RL-stabilized oil-in-water nanoemulsions (RL-NEs) for transporting antimicrobial essential oilslike tea tree, rue, and thyme. Dynamic Light Scattering measurements confirmed thestability of RL-NEs over several months, with an average droplet size between 200 - 400nm. Moreover, zeta potential measurements (-25 to -65 mV) demonstrated favorable electrostatic properties for the emulsion´s stability. Additionally, we assessed the RL-NEs wettability on freshly detached Arabidopsis thaliana leaves, revealing low contact anglesand suggesting increased wetting capacity and biological efficiency.On the other hand, to gain a comprehensive understanding of the effect of RLs onbiomimetic plant membranes, we conducted experiments utilizing Large Unilamellar Vesicles (LUVs). We evaluated the membrane permeability using carboxyfluorescein release, obtaining a 50% release at 148 μM RL-Nat concentration. Furthermore, we measured DPH (1,6-diphenyl-1,3,5, hexatriene) anisotropy and Laurdan GeneralPolarization (GP) at different RL-Nat concentrations. These measurements revealed that the interaction of RLs with the LUVs leads to membrane disorganization at a concentration close below its CMC, increasing its fluidity and surface hydration. Overall, these findings advance our understanding of RLs´ potential to enhance plant immunity and offer sustainable solutions for crop protection.