Biofabrication of gold nanoparticles by Lyptolyngbya JSC-1 extract as super reducing and stabilizing agents: Synthesis, characterization and antibacterial activity

This study describes the first ever utilization of cell free aqueous extract of cyanobacterium Leptolyngbya JSC-1 as a source of strong reducing and stabilizing agents for the optimal biofabrication of gold nanoparticles (AuNPs) through an eco-friendly synthetic route. Well dispersed crystalline AuNPs of spherical morphology with a particle size of 100-200 nm were prepared. FTIR spectral analysis was then performed to characterize the possible functionalities of JSC-1 extract, mainly involved in stabilizing and formation of AuNPs. Based on the redox potential of JSC-1 extract, it was further confirmed that the extract provide a strong reducing environment in the reaction medium and causes reduction of gold ions. The resultant AuNPs were then explored to find out their photo-catalytic activity for methylene blue and antibacterial activities against E. coli (18 +/- 2 mm) and S. aureus (14 +/- 2 mm). It has been mechanistically identified that AuNPs caused bacterial membrane damage and cell disruption by inducing the production of intracellular reactive oxygen species (ROS). Together, these finding reveals that biochemically capped AuNPs are the promising antibacterial agents that induce oxidative stress in the two bacterial species evaluated and cause their membrane disruption leading to cell leakage and death.