An evaluation of the activity of biologically synthesized silver nanoparticles against bacteria, fungi and mammalian cell lines

Biogenic silver nanoparticles are used for a number of applications due to their size, surface characteristics and strong antimicrobial properties. The present study aimed to investigate the synthesis of silver nanoparticles from the indigenous bacterial strain Bacillus sp. MB353 (PRJNA357966). Detailed characterization of silver nanoparticles was performed by UV–vis Spectrophotometer, FTIR, SEM and XRD. Biogenic silver nanoparticles were crystalline with average size 49−53 nm. These silver nanoparticles demonstrated good antibacterial activity against Gram-positive and Gram-negative bacteria (E. coli, Bacillus subtilis, Staphylococcus aureus, Klebsiella pneumoniae, Enterococcus faecium, Enterococcus faecalis and Streptomyces laurentii). The nanoparticles also showed excellent antifungal activity against Aspergillus niger, Aspergillus fumigatus, Fusarium soleni. The silver nanoparticles showed negligible antioxidant activity, but ROS generation pointed to a possible mode of antimicrobial activity. Incubation of silver nanoparticles with mammalian cell lines (Rhabdomyosarcomas and fibroblast) showed cell death and inhibition of proliferation. Cytotoxicity was most likely a result of ROS generation and changes in intracellular calcium levels. These findings suggested that biogenic silver nanoparticles could be used as alternative agents for biomedical purposes such as antibacterial and antifungal agents. However, given the effects on normal mammalian cells, it is probable that they could be used as anticancer agents if applied in targeted therapies