Synthesis and characterization of pullulan-mediated silver nanoparticles and its antimicrobial activities

Synthesis of silver nanoparticles was achieved using pullulan as both a reducing and stabilizing agent. The effect of pullulan and silver nitrate amounts on the synthesis of silver nanoparticles (AgNPs) was investigated. The formation of nanoparticles was first screened by measuring the surface plasmon resonance peak at 420-430 nm using UV-vis spectroscopy. The morphology of the synthesized AgNPs was determined using TEM, which indicated that the AgNPs varied in shape and polydispersed with an average size of 2-30 nm. The presence of elemental silver and the crystalline structure of the AgNPs were confirmed by EDX and XRD analyses. The possible functional groups of pullulan responsible for the reduction and stabilization of AgNPs were evaluated using FT-IR. The pullulan-reduced AgNPs showed excellent antibacterial, antifungal, and antibiofilm activity against food and multidrug resistant bacterial and fungal pathogens. The results showed that pullulan could be used as a reducing as well as a capping agent for synthesizing AgNPs which had potent antimicrobial activity.