Targeted Delivery of Thymoquinone‐Encapsulated Polyethyleneimine/Poly (Lactic Acid) Nanoparticles Into Breast Cancer Cells

Breast cancer is the most commonly diagnosed cancer globally, predominantly affecting older women. Thymoquinone (TQ) is a natural therapeutic agent that exerts anticancer efficacy. However, its pharmacological effects are restricted by inadequate aqueous solubility and bioavailability. The present study aimed to develop TQ-encapsulated polyethyleneimine/poly(lactic acid) nanoparticles (TQ-PEI/PLA-NPs) to enhance the delivery of TQ into breast cancer cells. The solvent evaporation-emulsification method was employed to synthesize TQ-PEI/PLA-NPs, and their physicochemical properties were subsequently examined. TQ-PEI/PLA-NPs had a crystalline structure, a zeta potential of +1 mV, and a spherical shape with a diameter of 80-90 nm. The encapsulation efficiency was 85.77 ± 2.21% (w/w), while the drug loading capacity was 9.32 ± 1.14% (w/w). The release rate of TQ from TQ-PEI/PLA-NPs was marginally elevated at pH: 5.8 (81.21 ± 0.87%) compared to pH 3.5 and 7.2. MTT assay using TQ-PEI/PLA-NPs confirmed concentration-dependent cytotoxicity against MCF-7 cells after 24 h of treatment, and IC₅₀ was found to be 21.99 μg/mL. The intracellular delivery of TQ in MCF-7 cells caused cell death, as indicated by AO/EBr staining, mitochondrial transmembrane potential assay, and Caspase-3 and -9 investigations. The observed MCF-7 cell death attributed to TQ was induced by reactive oxygen species (ROS) and impaired mitochondrial membrane potential. The ROS potentially damaged the mitochondrial membrane, and further studies supported the induction of apoptosis. Our results indicated that TQ-PEI/PLA-NPs, which cause cytotoxicity to breast cancer cells, as evidenced by the decreased MCF-7 cell counts, may exhibit significant therapeutic potential for breast cancer therapies.