Multifunctional Ag/MgO Nanocomposite from Marine Bacterium Bacillus tequilensis MYG163 EPS Triggers Metalloptosis in HepG2 Cells Through p53-Mediated DNA Damage and Caspase-3 Activation.

Contemporary cancer therapies encounter fundamental obstacles such as resistance development, systemic toxicity thresholds, inadequate tumor discrimination, and restricted treatment efficacy ranges. To synthesize biogenic Ag/MgO nanocomposite using marine bacterium Bacillus tequilensis MYG163 exopolysaccharide and evaluate its multifunctional therapeutic properties. Ag/MgO nanocomposite was synthesized via bacterial EPS-mediated biogenic route and characterized by UV-Vis, FT-IR, TEM, XRD, EDX, DLS, and zeta potential. Hemocompatibility, antioxidant capacity (DPPH, ABTS•+), anti-inflammatory activity (COX-1/COX-2 inhibition), and cytotoxicity against WI38 fibroblasts and four cancer cell lines, HepG2 (hepatocellular carcinoma), MCF-7 (breast cancer), HeLa (cervical cancer), and PC-3 (prostate cancer) were evaluated. Apoptotic mechanisms were examined through qRT-PCR, comet assay, diphenylamine assay, and flow cytometry. Biogenic synthesis using B. tequilensis MYG163 EPS yielded spherical Ag/MgO nanocomposite (10–50 nm), negative surface charge (-26.8 mV), hydrodynamic size of 56.8 nm containing 29.6 wt% silver and 8.8 wt% magnesium with face-centered cubic silver reflections and cubic periclase MgO structure. XRD confirmed crystalline phases at 38.04°, 43.32°, 62.65° (Ag) and 59.27°, 75.05° (MgO). Hemolysis remained ≤ 1.6% at 1000 µg/mL. Antioxidant IC₅₀: 22.22 µg/mL (DPPH), 17.38 µg/mL (ABTS•+). Anti-inflammatory IC₅₀: 110.67 µg/mL (COX-1), 167.47 µg/mL (COX-2). Cancer cell IC₅₀ ranged 61.12–149.51 µg/mL vs. 369.53 µg/mL (WI38). HepG2 treatment triggered p53 (378%), p21 (487%), Bax (297%), Caspase-3 (654%) upregulation, Bcl-2 (64%) downregulation, DNA damage (73% increase), S-phase arrest (42.80%), and G2/M block (8.35%). Bacterial EPS enables single-step synthesis of biocompatible Ag/MgO nanocomposite with integrated antioxidant, anti-inflammatory, and cancer-selective apoptotic properties, offering potential for targeted therapy development.