Green biosynthesis of silver nanoflowers using the Tithonia diversifolia leaf extract: in vitro anticancer activity, antimetastatic effects, and crystal violet photodegradation

Abstract

The convergence of cancer incidence, persistent infectious wounds, and environmental contamination by industrial dyes such as crystal violet underscores the need for sustainable nanomaterials that can support both biomedical and environmental applications. In this study, silver nanoflowers (AgNFs) were synthesized through a green aqueous route using the Tithonia diversifolia leaf extract (TDLE) as a reducing and stabilizing medium. This plant-mediated strategy was selected to minimize chemical input while exploiting the phytochemical constituents of TDLE for silver-ion reduction, surface capping, and hierarchical nanostructure formation. Ultraviolet-visible (UV-vis) spectroscopy showed a characteristic silver plasmonic absorption band, while Fourier transform infrared (FT-IR) spectroscopy supported the involvement of extract-derived hydroxyl, carbonyl, and carboxyl-containing functional groups in surface capping. X-ray diffraction (XRD) confirmed crystalline face-centered cubic silver with preferential reflection features, and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed radially assembled flower-like architectures composed of petal-like silver plates. Selected area electron diffraction (SAED) further supported the polycrystalline nature of the NFs, while zeta-potential analysis and dynamic light scattering (DLS) analysis indicated aqueous dispersion behaviour consistent with phytochemical-assisted electrosteric stabilization. Thermogravimetric analysis (TGA) confirmed the presence of surface-associated organic capping components, and Brunauer–Emmett–Teller (BET) analysis showed mesoporous textural features with a surface area of 36.7 m² g⁻¹, supporting accessible interfacial surface sites. Functionally, the TDLE-derived AgNFs (TD-AgNFs) showed concentration-dependent anticancer activity, with IC₅₀ values of 160, 230, and 260 µg mL⁻¹ against Huh7, THP-1, and SiHa cancer cell models, respectively. TD-AgNFs also reduced in vitro cancer cell migration under scratch and transwell assay conditions at 50 µg mL⁻¹. In addition, TD-AgNFs enabled rapid sunlight-assisted crystal violet photodegradation across 5–25 ppm, as estimated from UV-vis absorbance changes. Overall, the findings support TD-AgNFs as plant-derived hierarchical silver nanostructures with preliminary in vitro biomedical activity and sunlight-assisted dye-degradation performance, while further mechanistic, selectivity, and mineralization studies are required for deeper validation.