Phyto-mediated green synthesis of silver nanoparticles for structural characterization, cytocompatibility, antioxidant and anti-inflammatory evaluation

Silver nanoparticles (AgNPs) synthesised via green routes are gaining prominence as sustainable nanotherapeutics due to their reduced environmental burden and enhanced biocompatibility. In the present study, silver nanoparticles were synthesised using leaf extract of Vernonia amygdalina (VA-AgNPs) and comprehensively characterized using UV–Vis spectroscopy, FTIR, FESEM, AFM, DLS, zeta potential analysis, PXRD, and EDX. The VA-AgNPs exhibited a stable surface plasmon resonance (SPR) peak at 420 nm and did not red-shift over four months at neutral pH, indicating strong colloidal stability. Further characterization demonstrated phytochemical capping, predominantly spherical and smooth morphology, with an average nanoparticle size of 49.5 nm. The hydrodynamic diameter was 81.6 nm with a polydispersity index of 0.228 and a zeta potential of −21.3 ± 6.02 mV, suggesting moderate electrostatic stabilization. Nanoparticles were crystalline silver with a face-centred cubic structure and an estimated crystallite size of 45.92 nm. Biological evaluation showed that VA-AgNPs were non-cytotoxic to normal NIH-3T3 fibroblast cells and demonstrated an enhanced antioxidant activity (IC₅₀ = 30.5 ± 1.5 µg/mL). Nanoparticles showed good inhibition of intracellular reactive oxygen species production with IC 50 of 24.57 ± 2.4 μg/mL compared to the standard (11.2 ± 1.9 μg/mL). Collectively, these findings reveal that Malawian V. amygdalina could be an effective reducing and stabilizing agent for the production of stable phytochemical functionalized AgNPs with favourable cytocompatibility and robust redox-modulating bioactivity. The integration of long-term stability profiling with intracellular ROS inhibition provides mechanistic support for the potential of VA-AgNPs as antioxidant and anti-inflammatory nano agents for inflammation associated conditions.