Synergistic anti-breast cancer activity of simvastatin and thymoquinone encapsulated in nanostructured lipid carriers for enhanced therapeutic outcomes.

This study aims to study the combined anti-cancer effects of Simvastatin (SIM) and Thymoquinone (THY) against breast cancer cell lines and to develop and evaluate nanostructured lipid carriers (NLCs) encapsulating Simvastatin and Thymoquinone. Nanostructured lipid carriers (NLCs) co-loaded with Simvastatin and Thymoquinone were successfully formulated for enhanced anticancer activity. The formulations were characterised using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD) to determine particle morphology and crystallinity. Key physicochemical parameters, including mean particle size, polydispersity index (PDI), zeta potential, and drug loading capacity, were systematically evaluated. Encapsulation efficiency and in vitro drug release profiles were assessed using the dialysis bag diffusion method, while formulation stability was monitored at 4 °C, 25 °C, and 40 °C over a defined period. In vitro biological evaluations were conducted on MCF-7 and MDA-MB-231 breast cancer cell lines. Cytotoxic potential was determined through MTT assay and IC50 value estimation. Cellular uptake was visualised using fluorescence microscopy, and apoptosis induction was quantified via flow cytometry using Annexin V-FITC/PI dual staining. The results suggest that the co-delivery of Simvastatin and Thymoquinone via NLCs enhances intracellular drug accumulation and promotes apoptosis, highlighting their potential as a synergistic nanocarrier-based therapy for breast cancer treatment. The optimised SIM-THY-NLCs were spherical with mean diameter of 105.6 ± 4.2 nm, PDI of 0.214 ± 0.03, and zeta potential of -28.6 ± 2.1 mV. Encapsulation efficiencies were 89 ± 1.59% (SIM) and 91 ± 1.45% (THY). Sustained drug release over 24 h was observed (SIM: 40%, THY: 65%). The NLCs showed significantly improved cytotoxicity with IC₅₀ values of 2.56 µg/ml (MCF-7) and 1.23 µg/ml (MDA-MB-231), alongside enhanced cellular uptake and apoptosis. SIM-THY-NLCs significantly improve drug stability, release, and anticancer efficacy on breast cancer cells establishing them as a promising nanocarrier system for effective breast cancer therapy.