Green silver nanoparticles: enhanced antimicrobial and antibiofilm activity with effects on DNA replication and cell cytotoxicity

Biofabricated metal nanoparticles are biocompatible, inexpensive and eco-friendly. They find immense utility in the domain of biomedical and materials science. The present work focuses on the 'green' synthesis of silver nanoparticles (AgNPs) using the methanolic extract of Syzygium cumini leaf. AgNPs showed the characteristic surface plasmon resonance peak at 442 nm. The XRD pattern confirmed the formation of face centered cubic AgNPs. The nanoparticles were uniformly distributed within a narrow size range of 10-20 nm. The particles exhibited significant antimicrobial activity against a panel of pathogens like Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Mycobacterium smegmatis, Trichophyton rubrum, Aspergillus sp and Candida albicans. Alterations in membrane permeability of AgNP treated microbial cells were evident from scanning electron microscope images. The replication fidelity of small (1500 bp) DNA fragments in the presence of AgNPs was compromised in a dose-dependent fashion and addition of bovine serum albumin (BSA) to PCR reactions reversed the effect of AgNPs. Besides, the prepared nanoparticles inhibited biofilm formation in a wide range of AgNP concentrations. Significantly, cytotoxicity assays showed good compatibility of AgNPs with human embryonic kidney cells (HEK 293). In summary, the study suggests an eco-friendly, cost effective and biocompatible approach for synthesizing AgNPs, which may act as a potential template for designing novel antibacterial, antifungal and antibiofilm agents.