BackgroundIt is well-established that specific herbal plants contain natural active ingredients that have demonstrated anti-cancer potential. Therefore, they are considered highly beneficial as a potential adjuvant, alternative or complementary agent in anti-cancer therapy. However, the low chemical stability and limited bioavailability of 3, 3′-Diindolylmethane (DIM), a plant-derived compound used in clinical settings, limit its therapeutic applications. To overcome this challenge, researchers have focused on developing innovative approaches to improve DIM's biological activity, such as utilizing nanoformulations. Here, we investigated the potential benefits of coating DIM nanoparticles (DIM-NPs) with PEG/chitosan in the treatment of breast cancer. Our results demonstrate the molecular mechanism underlying the activity of DIM-NPs, highlighting their potential as an effective therapeutic strategy for breast cancer treatment. MethodsDIM-PLGA-PEG/chitosan NPs were synthesised and characterised using dynamic light scattering (DLS) and evaluated the impact of these NPs on two breast cancer cell models. ResultsDIM-NPs had an average diameter of 102.3 nm and a PDI of 0.182. When treated with DIM-NPs for 48 h, both MCF7 and MDA-MB-231 cells displayed cytotoxicity at a concentration of 6.25 g/mL compared to untreated cells. Furthermore, in MDA-MB-231 cells, treatment with 2.5 μg/mL of DIM-NPs resulted in a significant decrease in cell migration, propagation, and angiogenesis which was further enhanced at 10 μg/mL. In chicken embryos, treatment with 5 μg/mL of DIM-NPs on day 2 led to a significant reduction in angiogenesis. Furthermore, this treatment induced cell death through a regulatory pathway involving the upregulation of Bax and p53, as well as the downregulation of Bcl-2. These results were supported by in-silico analysis of DIM's binding affinity to key proteins involved in this pathway, namely Bax, Bcl-2, and p53. ConclusionOur findings show that DIM-NPs induces apoptosis, inhibit migration, and reduce angiogenesis in breast cancer. However, further research using a preclinical cancer model may be necessary to determine the pharmacokinetics of DIM-NPs and ensure their safety and efficacy in vivo.