Eco-friendly Fabrication of Silver Nanoparticles Using Echinops spinosissimus Seeds Extract: Optimization, Characterization, Antibacterial Efficacy, and Nano- Induced Red Blood Cell Hemolysis

Abstract

     The silver nanoparticles (AgNPs) were synthesized in aqueous media by means of an aqueous extract from Echinops spinosissimus seeds, and the optimization of the synthesis conditions was carried out at: 10 mL of extract + 10 mL of AgNO₃ (0.02 M), pH = 7, T = 70 °C during 60 minutes. The characterization of the product was performed through techniques such as UV-Vis spectroscopy, infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The UV-Vis spectroscopy spectra showed a surface plasmonic resonance band characteristic of the metallic core of the nanomaterials; the FTIR data provided evidence of the presence of phytochemical molecules capping the AgNPs; finally, the SEM micrographs showed that the majority of the synthesized AgNPs had a spherical morphology, while some of them exhibited a rod-like shape (diameter range 46.69–71.99 nm). To evaluate the antimicrobial potential of the AgNPs synthesized, agar diffusion assays were conducted against three strains of bacteria (Escherichia coli, Klebsiella spp., Staphylococcus aureus) and two strains of fungi (Candida spp.). The results obtained from these assays showed a concentration-dependent inhibition of bacterial and fungal growth, and the mean diameters of the inhibition zones ranged approximately from 14–18 mm for both types of microorganisms tested. The hemocompatibility of the AgNPs was assessed using purified human red blood cells exposed to different doses of the synthesized AgNPs. A progressive increase in hemolysis was observed as a function of the increasing dose of AgNPs, which enabled to determine a "safe" window of application for the use of AgNPs as antimicrobial agents, balancing their efficacy against bacteria and fungi with their potential toxicity to humans.