Silver nanoparticles synthesized with green methods using spruce plant extract and their synergistic antibacterial activity

Abstract This study investigates the antibacterial efficacy of silver nanoparticles (AgNPs) synthesized using spruce needle extract, comparing the performance of AgNPs with residual plant extract to that of purified AgNPs. Scanning electron microscopy revealed nanoparticles mostly spherical in shape with an average diameter ranging from 16.8nm (nanoparticles in plant extract medium) to 22.6 (pure nanoparticles). Antibacterial tests with the food product showed that the nanoparticles in the plant extract completely inhibited the growth of microorganisms, while in the case of pure nanoparticles a slight microbial growth was observed (34, 7, 41 colonies). This antibacterial activity may be due to the synergistic effect of silver nanoparticles with bioactive compounds found in spruce needle extract - phenolic compounds, flavonoids. They can act as a stabilising medium for nanoparticles and enhance the interaction with bacteria. Also, the high temperatures used purify nanoparticles could cause sticking and agglomeration of the particles, reducing their antibacterial activity. These findings suggest that the use of plant extracts is rational for the synthesis of metallic nanoparticles, and is applicable in the food industry, where effective and non-hazardous antibacterial agents are required.