Extracellular Biosynthesis, Characterization and Cytotoxic Effect of Silver Nanoparticles by KS-3.

The present work aimed to investigate extracellular biosynthesis of silver nanoparticles (AgNPs) mediated by an actinomycete strain and their cytotoxic effects compared with silver ions. The selected strain was identified as Streptomyces coelicoflavus KS-3 by phenotypical characteristics and 16S rRNA analysis. The formation of biosynthesized AgNPs was proved by an absorption peak observed at 437 nm. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) analyses revealed that the prepared AgNPs were spherical or approximately spherical followed by a small amount of truncated triangular, quadrangular and hexagonal with the particle diameters ranging from 2.33 to 91.3 nm. X-ray diffraction (XRD) pattern confirmed that the AgNPs presented a face-centered cubic (FCC) structure of crystalline silver. Energy dispersive of X-ray (EDX) spectrum and Fourier transform infrared spectroscopy (FTIR) analyses verified the existence of biomolecules, such as proteins, that participated in the formation and stabilization of AgNPs. Furthermore, the comparative study on cytotoxic effect of AgNPs indicated that the AgNPs exhibited higher biocompatibility towards human bronchial epithelial (HBE) cells than silver ions and exerted potent cytotoxic effect in a dose-dependent manner against human lung squamous cell carcinoma cells (HTB-182) and human lung adenocarcinoma cells (A549) with the concentrations ranging from 1 to 50 μg/mL.