Plant‐Mediated Silver Nanoparticles From Thymus vulgaris and Citrus sinensis : Comparative Antibacterial Activity, Cytocompatibility, and In Vitro TMPRSS2 Inhibitory Activity

ABSTRACT Green‐synthesized silver nanoparticles (AgNPs) have attracted interest due to their favorable physicochemical properties and broad‐spectrum biological activities. This study comparatively synthesized and characterized AgNPs using aqueous extracts of Thymus vulgaris (TV) and Citrus sinensis (CS), evaluating their antibacterial activity, cytocompatibility, and in vitro inhibitory activity against transmembrane serine protease 2 (TMPRSS2). Phenolic profiles were analyzed by HPLC, and physicochemical characterization (UV–vis, FTIR, XRD, TEM, DLS) confirmed the formation of crystalline face‐centered cubic silver nanostructures. XRD revealed average crystallite sizes of 7.37 ± 2.53 nm for TV_AgNPs and 4.18 ± 1.60 nm for CS_AgNPs, while TEM showed particle diameters of 11.77 ± 2.32 nm and 11.02 ± 1.97 nm, respectively; DLS yielded hydrodynamic diameters of 92.04 nm and 98.40 nm. Both nanoparticle systems exhibited concentration‐dependent antibacterial activity against Escherichia coli , with TV_AgNPs showing greater inhibition, and demonstrated high cytocompatibility in L929 fibroblasts. Furthermore, TV_AgNPs and CS_AgNPs inhibited TMPRSS2 by 62.0% and 70.0%, respectively, at 100 µg/mL. These findings indicate that plant‐mediated AgNPs exhibit promising antibacterial activity, favorable cytocompatibility, and in vitro TMPRSS2 inhibitory activity, highlighting the influence of botanical sources on their physicochemical and biological characteristics.