Green synthesis, characterization and antibacterial activity of silver nanoparticles using Acanthus ilicifolius leaf extract

The green biosynthesis of silver nanoparticles (AgNPs) using plants has become a promising approach for developing potent agents against fatal pathogens. The present study evaluated the green production of silver nanoparticles (AgNPs) from the extract of Acanthus ilicifolius leaves and their antibacterial properties as a sustainable solution to bacterial challenges in shrimp aquaculture. The synthesis of AgNPs was confirmed after 6 hours by monitoring a color change. Ultraviolet–visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) analysis were employed to characterize the synthesized particles. The UV-vis spectrum of the synthesized silver nanoparticles exhibited a characteristic absorption peak at λmax = 400 nm, confirmed the successful formation of AgNPs. FTIR analysis indicated potential interactions between silver and bioactive compounds in A. ilicifolius leaf extracts, which may facilitate the formation and stabilization of silver nanoparticles. SEM imaging revealed that the particles were spherical and exhibited no aggregation. AFM topography showed that the AgNPs were spherical, polydisperse particles with an average size of 86.86 nm. The nanoparticles demonstrated stronger antibacterial efficacy against harmful bacteria through disk diffusion assays, with inhibition zones of 15±0.8 mm for Vibrio parahaemolyticus at a 1000 mg/mL concentration, 12±0.4 mm for Pseudoalteromonas ostreae at 250 mg/mL, and 13±0.7 mm for Shewanella khirikhana at 250 mg/mL. Vibrio parahaemolyticus exhibited the greatest vulnerability at this dose, while showing resistance to the antibiotic oxytetracycline at 30 μg. The strong bioactivity of the green produced AgNPs from this plant suggests their application in biomedicine as antibacterial agents in shrimp aquaculture.