Novel keratin-based particles encapsulating essential oils: A step towards developing sustainable biopesticides

Essential oils (EOs) are playing a pivotal role in pest control within biologic farming due to their botanical origin and potential as biocontrol agents. However, their use is still limited by challenges like high volatility, rapid oxidation, and susceptibility to degradation in field conditions. Additionally, EOs might present some health risks to humans through inhalation or direct contact during application. Encapsulation of EOs holds promise by enhancing essential stability and activity, while reducing their volatility and potential cytotoxicity. EOs from Satureja montana (Winter Savory), Mentha piperita (Peppermint) and Thymus vulgaris (Thyme) were investigated, both in their free form or encapsulated into keratin-based particles, representing a novel class of biopesticides. Particles containing 15 mg/mL of keratin encapsulating the EOs were stable over time with sizes below 650 nm and demonstrated particle formation and encapsulation efficiencies higher than 90 %. The keratin-based particles exhibited a release of approximately 12 %, 43 %, and 51 % for M. piperita EO, S. montana EO, and T. vulgaris EO, respectively, during a 48-hour in vitro evaluation. When tested for cytotoxicity in human fibroblast cells, the free EOs exhibited greater cytotoxic effects compared to their encapsulated forms, especially at higher concentrations. Encapsulation of EOs into keratin-based particles significantly reduced their harmful impact on cells, demonstrating the protective effect of these formulations. This reduction in cytotoxicity suggests potential for further exploration of these encapsulated EOs as alternatives to conventional pesticides. However, their efficacy against pests and their toxicity towards non-target species requires further validation.