CHITOSAN-TREATED SOLID LIPID NANOPARTICLES LOADED WITH ESSENTIAL OILS: PHYSICOCHEMICAL CHARACTERIZATION AND PRELIMINARY IN VITRO ANTIOXIDANT SCREENING

Abstract

Diseases transmitted by mosquitoes continue to be a public health issue, leading to increased interest in plant-derived substitutes for artificial repellents. Essential oils show potential, yet their volatility restricts the duration of protection, and lipid nanoparticles could assist in transporting them. We formulated solid lipid nanoparticles (SLNs) containing a blend of three oils: Melissa officinalis, Lavandula angustifolia, and Eucalyptus globulus oils, and assessed uncoated SLNs against chitosan-treated SLNs (CSLNs). Chitosan treatment decreased the total hydrodynamic diameter from 410.3 to 245.2 nm, tightened the size distribution (PDI 21.6% to 16.3%), and raised the dominant intensity population from 80.10% to 97.88%. FTIR spectra revealed band displacements that align with interactions between the components. In the DPPH assay at 100–400 µg/mL, CSLNs mitigated 45.4–77.6% of radicals, while uncoated SLNs scavenged 3.6–38.4%. Chitosan treatment consequently altered the antioxidant and protein-stabilizing characteristics of the formulation in various ways, resulting in lower encapsulation estimates for CSLNs. This trade-off highlights chitosan concentration as a design variable to optimize, aiming to enhance both radical scavenging strength and oil retention. Collectively, these findings encourage the continued advancement of chitosan-treated SLNs as a potential environmentally friendly mosquito repellent; their repellent effectiveness has yet to be evaluated.