Nigella sativa L. essential oil-loaded chitosan nanoparticles: Physicochemical characterization, biological activities, and in silico insights

Nigella sativa essential oil (NSEO), rich in the bioactive compound thymoquinone (TQ), possesses potent antioxidant and anticancer properties; however, its practical utility is hindered by high volatility and poor aqueous solubility. To overcome these limitations, NSEO was encapsulated within chitosan-tripolyphosphate (Ch-TPP) nanoparticles via oil-in-water emulsification and ionic gelation. The resulting nanocarriers exhibited mean diameters of 167.0–209.5 nm, narrow polydispersity (PDI ≤ 0.391), and high positive surface charges (> +30 mV), ensuring robust colloidal stability. Functionally, nanoencapsulation significantly amplified the essential oil's antioxidant capacity, yielding maximal DPPH and CUPRAC values of 2.888 and 3.665 mM Trolox equivalents, respectively. Furthermore, in vitro evaluations demonstrated enhanced cytotoxic efficacy, reducing SH-SY5Y neuroblastoma cell viability to below 20% after a 48 hours exposure. Mechanistically, molecular docking revealed strong binding affinities of TQ and the chitosan matrix toward the VEGFR2 and Keap1 Kelch domains. These high-affinity interactions were comprehensively validated by 100 ns molecular dynamics simulations, confirming the enduring structural stability of the functional complexes. Overall, this integrated experimental and in silico study establishes Ch-TPP nanoencapsulation as a highly effective strategy to preserve and potentiate the therapeutic efficacy of NSEO for advanced pharmaceutical applications.