Plant‑mediated silver quantum dots from Drimia maritima: antioxidant modulation and ROS‑induced apoptosis in breast...

Green nanotechnology offers a sustainable approach to improving the therapeutic efficacy of plant‑derived bioactive compounds while reducing environmental and biological toxicity. In this study, silver quantum dots (Ag QDs) were synthesized via an eco‑friendly green route using the aqueous bulb extract of Drimia maritima (L.) Stearn (D. maritima), which served as a natural reducing and stabilizing agent. Physicochemical characterization confirmed the successful formation of well‑defined nanoscale Ag QDs with appropriate structural features. The antioxidant potential of the biosynthesized Ag QDs was systematically evaluated using various in vitro assays, including DPPH, ABTS, nitric oxide scavenging, ferric reducing antioxidant power (FRAP), and metal‑chelating activity. The results revealed a dual antioxidant behavior: Ag QDs showed enhanced free‑radical scavenging capacity, whereas the crude extract exhibited stronger reducing and chelating activities. The anticancer efficacy of Ag QDs was assessed in MCF‑7 human breast cancer cells. MTT assay results revealed a significant cytotoxic effect, with an IC₅₀ value of approximately 14.7 µg/mL, approaching that of cisplatin and markedly lower than that of the crude extract. Mechanistic studies indicated that Ag QDs induced excessive intracellular ROS generation, leading to mitochondrial dysfunction and activation of the intrinsic apoptotic pathway, characterized by pronounced caspase‑9 and caspase‑3 activation. These effects were accompanied by modulation of apoptosis‑ and redox‑related gene expression, favoring pro‑apoptotic signaling. Confocal microscopy further confirmed apoptotic morphology, including chromatin condensation and cytoskeletal disruption. Overall, D. maritima‑derived Ag QDs emerge as potent pro‑oxidant nanostructures capable of inducing ROS‑mediated mitochondrial apoptosis, highlighting their promise as a sustainable nanotherapeutic platform for breast cancer treatment.