The interaction of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) Langmuir monolayers as a model biomembrane with small silver nanoparticles (AgNPs) similar in size but coated with different capping molecules such as citrate (CIT-AgNPs) and 4-mercaptobenzoic acid (MBA-AgNPs), both negatively charged at physiological pH, is studied using a multi-technique approach. Both CIT-AgNPs and MBA-AgNPs expose carboxyl groups and have similar zeta potentials, but differ in the aliphatic or aromatic nature of the capping agent. Results show that AgNPs exhibit quite different behaviors: CIT-AgNPs weakly adsorb on DMPC, while MBA-AgNPs irreversibly adsorb on the interface and remain there upon monolayer compression. It is also shown that there is a cooperative effect of many ligands in the interactions between MBA-AgNPs and DMPC, as MBA molecules in solution are unable to strongly adsorb on the phospholipid monolayer surface. We propose an explanation based on the surface charge density and on the chemical nature of the capping molecule based on XPS studies and on DFT calculations.

The search for environmentally friendly solutions to effectively control crop pests while safeguarding human health has become a global priority. One promising strategy is to enhance plant defenses by pre-inducing their innate immune system. In this study, we developed rhamnolipid (RL)-stabilized nanoemulsions (NEs) encapsulating essential oils (EOs) as potential biopesticides and biostimulants for agroindustrial applications. These NEs were designed to improve the solubility and stability of EOs while effectively combining their insecticidal and/or repellent activities with the bioactive properties of RLs. In this regard, our interdisciplinary approach involved formulating and characterizing these NEs and evaluating their stability and wettability on plant leaf surfaces. We further evaluated their effects on bacterial growth in vitro and in the model plant Arabidopsis thaliana, along with their impact on beneficial soil microorganisms. We analyzed their ability to stimulate the plant’s immune system and their impact on the viability and reproduction of the aphid Myzus persicae. Additionally, we explored whether RLs stimulate plant defenses through alterations in the leaf cuticle. Our findings demonstrate that RL-stabilized EO-NEs are effective bioprotectants and biostimulants in the model plant, offering a sustainable alternative that could reduce reliance on chemical pesticides in agriculture.