Synthesis and characterization of Terminalia arjuna bark extract-based silver nanoparticles: process parameters optimization using response surface methodology and evaluation of antibacterial activity

Nanoparticles (NPs) synthesized by the green synthesis approach have appeared as an environmentally friendly and sustainable strategy in the past decade. In this process, the bark extract of Terminalia arjuna (T. arjuna) functions as a reducing and capping agent for synthesizing silver nanoparticles (AgNPs). Different bioactive compounds, such as saponins, tannins, and flavonoids from bark extract, play an essential role in nanoparticle synthesis and stabilization. The appearance of a dark brown color in the solution visually confirms the nanoparticle formation. Furthermore, an absorbance peak at 410 nm wavelength confirms the biosynthesis of AgNPs. Moreover, process parameters (temperature, stirring time, and silver nitrate concentration) for nanoparticle synthesis were statistically optimized by using the response surface methodology (RSM) tool. The maximum synthesis of nanoparticles was achieved at 5 mM silver nitrate, 80° C temperature, and 40 minutes of stirring time. The spherical structure of AgNPs, with a size range of 10-120 nm and an average particle size of 36 nm, was discovered from transmission electron microscopy (TEM). Also, the X-ray diffraction (XRD) technique indicated the crystalline nature of synthesized AgNPs. Moreover, the antibacterial potential of silver nanoparticles was tested against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), which exhibit significant inhibition zones and advocate using AgNPs against antibiotic-resistant strains. This study reveals the capability of T. arjuna bark extracts in the biogenic synthesis of NPs with high antibacterial potential, which can be employed in different biomedical applications.

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