Influence of abiotic conditions on synthesis of silver nanoparticles using Verbascum scamandri

Green synthesis involves the biological production of metallic nanoparticles using plants or plant extracts. In our study, we investigated the effect of altitude on synthesizing silver nanoparticles (AgNPs) from Verbascum scamandri plants collected at two distinct altitudes in Bayramiç, Çanakkale, Türkiye (V1: 675 m, V2: 800 m) and from in vitro grown samples (V3), using a green synthesis method. UV-Vis spectroscopy confirmed the formation of AgNPs with peak absorption between 428-432 nm. Zeta potential analysis showed that AgNPs had negative surface charges, indicating stability. The sizes of nanoparticles varied significantly, with V3-AgNPs exhibiting the largest average size of 242.7 nm, and V2-AgNPs the smallest at 125.1 nm. FTIR analysis revealed functional groups responsible for reduction, including -OH, -CN, and C=O bonds. SEM and TEM analyses confirmed spherical AgNPs with sizes ranging from 20-97 nm. EDX analysis indicated high Ag content, with V3-AgNPs showing 87.79% Ag. The antimicrobial activity of AgNPs was assessed against various bacterial and fungal strains. The minimum inhibition concentrations (MIC) ranged from 0.62 to 5.0 µg/mL, with V3-AgNPs showing the highest activity against Acinetobacter baumanii (MIC = 0.62 µg/mL). The biofilm inhibition percentage varied, with V3-AgNPs demonstrating the highest inhibition against A. baumanii (82.05%) and Escherichia coli (76.12%). Altitude and environmental factors influenced AgNP synthesis, with the highest particle sizes from lower altitudes and roadside samples.