Eugenol-loaded zinc oxide nanoparticles enhance paclitaxel sensitivity in breast Cancer cells: A combined synergistic nanomedicine and theoretical approach

Zinc oxide nanoparticles (ZnO NPs) have emerged as promising nanocarriers for enhancing drug delivery efficiency and reducing the side effects of conventional chemotherapy. Eugenol, a bioactive phenolic compound with anti-inflammatory, antioxidant, and anticancer properties, has shown potential as a therapeutic adjuvant. This study aimed to compare the anticancer efficacy of eugenol-loaded ZnO NPs (ZnO@Eug), alone and in combination with paclitaxel, against breast cancer cells. ZnO NPs were synthesized and characterized using FTIR, XRD, DLS, Zeta potential, FE-SEM, and TEM. The average particle size was 183 nm with a polydispersity index of 0.5 and a zeta potential of −45 mV. Eugenol loading efficiency reached ∼91 %, with a pH-dependent release profile showing enhanced release at pH 4.5. MCF7 and MDA-MB-231 breast cancer cell lines were treated with free eugenol, ZnO NPs, ZnO@Eug, paclitaxel, and their combination. Cell viability (MTT assay), migration (scratch assay), apoptosis (flow cytometry, caspase 3/7), colony formation, and gene expression (KRAS, CDC25A via RT-qPCR) were evaluated. Results showed that ZnO@Eug combined with paclitaxel significantly decreased cell viability, migration, and clonogenic potential while enhancing apoptosis, compared to monotherapies. The combination index (CI < 1) indicated a synergistic effect between ZnO@Eug and paclitaxel. These findings highlight the potential of ZnO NPs as a delivery platform for eugenol and support the use of this combination strategy to improve chemotherapy outcomes in breast cancer. Furthermore, the ground-state configurations and electronic characteristics of ZnO@Eug were optimized using DFT at the B3LYP level. To explore the anticancer activity of ZnO@Eug and paclitaxel, a molecular docking study was carried out targeting the HER2 protein. • ZnO nanoparticles (∼183 nm, −45 mV zeta potential) achieved ∼91 % eugenol loading efficiency with pH-sensitive release. • ZnO@Eug combined with paclitaxel significantly reduced breast cancer cell viability, migration, and colony formation. • Combination index (CI < 1) indicated a -synergistic between ZnO@Eug and paclitaxel, enhancing apoptosis and downregulating -KRAS and CDC25A. • DFT optimization and HER2-targeted molecular docking revealed favorable interactions, supporting ZnO@Eug as an effective nanocarrier.