Enhanced therapeutic efficacy of Tamoxifen against breast cancer using extra virgin olive oil-based nanoemulsion delivery system

Breast cancer remains a leading cause of cancer-related deaths worldwide, requiring innovative therapeutic approaches. This study investigated the development and characterization of an olive oil-based nanoemulsion system for enhanced tamoxifen (TMX) delivery in breast cancer treatment, pointing to the limitations of poor water solubility and bioavailability of free TMX. Extra virgin olive oil (EVOO) was initially characterized by high-performance liquid chromatography analysis, confirming its high content of oleic acid (65.45%). The oil-in-water nanoemulsion system [NE(OST) + TMX] was successfully formulated using EVOO (oil phase) with surfactants, i.e., Tween-80 and Span-20. NE(OST) + TMX exhibited excellent physical stability with a particle size of 179.76 ± 9.6 nm, a polydispersity index of 0.184, and a zeta potential of −30.52 mV. NE(OST) + TMX demonstrated high entrapment efficiency (97.5 ± 4.25%) and a controlled release profile, achieving complete release within 24 h, to improve drug penetration and cellular uptake in cancer cells while reducing systemic toxicity. NE(OST) + TMX showed reduced in vitro hemolytic activity compared to free TMX, indicating improved biocompatibility. The cytotoxicity test showed a better antiproliferative effect against MCF-7 cells with NE(OST) + TMX (IC₅₀ = 49.23 μg mL⁻¹) compared to free TMX (IC₅₀ = 90.12 μg mL⁻¹), while exhibiting reduced toxicity toward normal HdFn cells. Fluorescence microscopy confirmed superior cellular uptake of NE(OST) + TMX. Flow cytometry analysis demonstrated that NE(OST) + TMX significantly increased apoptosis induction and G₀/G₁ phase cell cycle arrest compared to free TMX. NE(OST) + TMX exhibited enhanced inhibition of cell migration in wound healing assays. NE(OST) + TMX upregulated BAX and Caspase-3 and downregulated BCL-2, confirming its molecular-level apoptotic efficacy. These results demonstrate that the olive oil nanoemulsion system significantly enhances TMX therapeutic efficacy while improving biocompatibility for breast cancer treatment.