Biosynthesis of silver and gold nanoparticles using Annona squamosa seed extract: Insights into antibacterial and anticancer activities

This study reports on the green synthesis of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) using Annona squamosa seed extract and the evaluation of their antibacterial and anticancer activities. The synthesized NPs were characterized by UV‑Vis spectroscopy, transmission electron microscopy, particle size and size distribution analysis, X‑ray diffraction, Fourier‑Transform Infrared Spectroscopy and Inductively Coupled Plasma‑Optical Emission Spectrometry. Characterization results confirmed the successful synthesis of spherical, crystalline NPs with mean hydrodynamic diameters of AgNPs and AuNPs determined as 40.60 and 72.65 nm, respectively. Antibacterial activity was assessed against Staphylococcus aureus and Escherichia coli, while anticancer activity was evaluated using MCF‑7 breast cancer cells and 293 cells. AgNPs exhibited significant antibacterial activity against both bacterial species, showing bacteriostatic activity against S. aureus and bactericidal activity against E. coli. By contrast, AuNPs showed no detectable antibacterial effect. AgNPs also demonstrated selective anticancer activity, inhibiting MCF‑7 cell proliferation in a dose‑ and time‑dependent manner with IC₅₀ values of 106.704 and 79.519 µg/ml after 48 and 72 h of treatment, respectively, while exhibiting minimal toxicity toward 293 cells. Furthermore, AgNPs modulated the expression of several cancer‑related genes, suppressed oncogenic markers and induced apoptosis through activation of p53‑associated pathways, as evidenced by increased apoptotic cell populations and an elevated BAX/BCL2 ratio. Conversely, AuNPs displayed limited biological activity under the tested conditions. These findings highlight the potential of A. squamosa‑mediated AgNPs as promising antibacterial and selective anticancer agents for future biomedical applications.