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Description
Silver nanoparticles (AgNPs) offer potent oncological potential via tunable SPR, yet conventional toxicity remains a challenge. This study evaluates biogenic synthesis and photoactivation as safer, targeted alternatives for MCF-7 and MDA-MB-231 breast cancer cells. Specifically, plant-mediated (biogenic) and chemically synthesized AgNPs were evaluated as wavelength-activated nanotherapeutics under matched surface plasmon resonance excitation conditions. Biogenic AgNPs exhibited an SPR maximum at ~466 nm, whereas chemically synthesized AgNPs displayed a peak at ~401 nm. Upon irradiation at 470 nm (biogenic) and 405 nm (chemical) with a fluence of 5 J/cm², distinct photophysical and biological responses were observed.
Chemically synthesized AgNPs demonstrated modest photothermal conversion (ΔT ≈ 2.8 °C), while biogenic AgNPs showed negligible thermal elevation (<1 °C), indicating minimal reliance on hyperthermic mechanisms. However, biogenic AgNPs generated substantially higher photoinduced reactive oxygen species (ROS), producing approximately threefold greater total ROS relative to chemically synthesized counterparts under matched irradiation conditions. This enhanced photo-oxidative activity translated into significant reductions in cell viability. In MCF-7 cells, photoactivation of biogenic AgNPs reduced the IC50 to <2 µg/mL, compared with 2.89 ± 0.20 µg/mL under dark conditions. In MDA-MB-231 cells, irradiation lowered the IC50 from 11.26 ± 0.04 µg/mL (dark) to 4.79 ± 0.05 µg/ml. Flow cytometric analysis confirmed apoptosis as the predominant mechanism of cell death, with late apoptotic populations approaching ~40% following photoactivation.
These results indicate that biogenic AgNPs induce ROS-mediated phototoxicity at lower doses, achieving effective cytotoxicity under visible-light activation without significant thermal effects, supporting their translational potential in cancer treatment.
