Extracellular Biosynthesis of Silver Nanoparticles from Soil-isolated Streptomyces sp. NBrR7 and its Antibacterial and Anticancer Activities

Abstract

Silver nanoparticles (AgNPs) have gained considerable attention in the field of medicine owing to their physiochemical properties. Actinomycetes are efficient microbe for metal nanoparticle production extracellularly and intracellularly. In this regard, the extracellular biosynthesis of AgNPs by a Streptomyces sp. isolated from the rhizosphere soil in Saudi Arabia was achieved. Eleven actinomycete isolates coded NBrR1. to NBrR11 were isolated and purified on starch nitrate agar medium. Screening the filtrates of these isolates for the biosynthesis of AgNPs revealed that, only 4 isolates exhibited various bioreduction degrees of Ag+ in aqueous solution as suggested by initial changes in the color of the solution. Among them, NBrR7 was selected as the most potent-isolate and identified based on the cultural, morphological as well as the physiological and biochemical characteristics which indicated belonging of this isolate to the genus Streptomyces and designated as Streptomyces sp. NBrR7. The microbiologically synthesized AgNPs showed promising antibacterial activity, especially against P.aeruginosa and B.subtilis. Promising cytotoxic activity was recorded for AgNPs against number of human cancer cell lines where it showed strong cytotoxicity against colon carcinoma (HCT-u6) with IC50 21.8 mu g/ml, moderate activity against liver carcinoma (HEPG2) with IC50 39.5 mu g/ml Hind while it was weak against breast adenocarcinoma (MCF-7) with IC50 47.80 pg/ml. The microbiologically synthesized AgNPs obtained from the lorally isolated Streptomyces sp. NBrR7 has lower toxicityand excellent biomedical applications.