Mechanistic insights into apoptosis induced by green synthesized liposomal gold nanoparticles enhancing photodynamic therapy in triple-negative breast cancer

Breast cancer still presents a major challenge in oncology, even with treatment advances. Its complexity is attributed to high mortality, late-stage diagnosis, and the development of resistance to conventional therapies such as surgery, chemotherapy, radiation, and hormone therapy. As many patients continue to experience treatment failure, recurrence, and disease progression, novel therapeutic approaches are urgently needed. This study investigates the potential of green-synthesized, liposome coated gold nanoparticles encapsulating pheophorbide-a (AuNPs-LIP-PPBa) to enhance photodynamic therapy (PDT) in triple-negative breast cancer (MDA-MB-231) cells. Pheophorbide-a (PPBa), a chlorophyll derivative, is a potent photosensitizer with strong absorption in the 650–700 nm range, enabling deeper tissue penetration. However, its clinical application is limited by poor cellular uptake and rapid clearance. To overcome these limitations, AuNPs were incorporated into liposome-PPBa complexes to improve photostability, uptake, and controlled release, while liposomes provided biocompatibility and targeted delivery. UV–Vis spectroscopy confirmed that the nanoformulation remained photostable for six weeks. Subcellular localization studies demonstrated preferential accumulation in lysosomes, mitochondria, and the endoplasmic reticulum, indicating efficient intracellular delivery. Live/dead assays showed strong phototoxicity under 660 nm laser irradiation with minimal dark toxicity. Apoptosis induction was confirmed by cytochrome c ELISA, caspase-3, −8, and − 9 activity assays, and flow cytometry, suggesting activation of both intrinsic and extrinsic pathways. Further validation through immunofluorescence and real-time PCR revealed regulation of apoptotic and anti-apoptotic markers. One-way ANOVA demonstrated significant differences between treated and control groups.