Gazania rigens (L.) gaertn leaf extract-inspired innovative synthesis of silver nanoparticles and promising applications as antibacterial and cytotoxic agents

Introduction: Silver nanoparticles are potent nanomaterials with significant applications in combating microbial infections and cancer. In this study, the extract of Gazania rigens var. uniflora was evaluated as a biogenic agent for the synthesis (G-AgNPs), and their biological activity was systematically assessed. Additionally, association of the antibiotic ampicillin and biogenic silver nanoparticles was developed to explore potential additive antibacterial effects, which has not been previously reported for this species. Methods: Silver nanoparticles were synthesized using a combination of the plant leaf extract and silver nitrate solution. Several characterization techniques, including dynamic light scattering (DLS), transmission electron Microscope (TEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FTIR) spectroscopy, were employed to analyze the synthesized nanoparticles. Results: DLS results indicated the presence of spherical, monodispersed nanoparticles with a mean diameter of 135.4 nm and a polydispersity index of 0.223, while TEM revealed sizes ranging from 14 to 44 nm. FTIR and EDX analyses confirmed the presence of phytochemical capping agents and elemental silver, supporting successful green synthesis. Both biogenic silver nanoparticles and ampicillin-associated G-AgNPs demonstrated antibacterial activity against Staphylococcus aureus, Streptococcus mutans, and Escherichia coli, with the ampicillin-associated G-AgNPs exhibiting a partial additive effect. Cytotoxicity assays demonstrated that G-AgNPs exerted significantly higher toxicity toward the breast cancer cell line MDA-MB-231 compared to non-cancerous breast epithelial cells. Discussion: Overall, this work distinguishes itself by integrating detailed physicochemical characterization with both antibacterial and anticancer evaluations, as well as by examining antibiotic-associated G-AgNPs synthesized using G. rigens. These findings support the potential biomedical relevance of G. rigens-derived AgNPs and justify further mechanistic and in vivo investigations.