Digest Journal of Nanomaterials and Biostructures Vol. 10, No. 2, April - June 2015, p. 385 - 392 SYNTHESIS OF SILVER NANOPARTICLES DISCOURAGE THE GROWTH OF ISOLATED BACTERIA INVADING THE BLOOD STREAM MASHAIL F.S. ALSAYED a , ALIA A. SHOEIB a,b , AWATIF A. HINDI c , MANAL A. AWAD d* , KHALID M. O. ORTASHI e a Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, KSA b Department of Plant Pathology, Faculty of Agriculture, Alexandria University, Egypt c Department of Physics and Astronomy, King Saud University, Riyadh, KSA d King Abdullah Institute for Nanotechnology, King Saud University, Riyadh, KSA e Department of Chemical Engineering, College of Engineering, King Saud University, Riyadh, KSA Silver Nanoparticles (Ag NPs) have strong antibacterial activities, for that it is very useful for medical applications. Stable silver nanoparticles were synthesized using sodium borohydride (NaBH4) and PVP as reducing and stabilizing agent respectively. Their shape and size distribution characterized by UV-vis spectrophotometer, scanning electron microscopy (SEM) equipped with the energy dispersive spectroscopy (EDS)and (TEM) transmission electron microscopic study their shape and size(< 20nm).The activity of Ag nanoparticles was investigated against isolated bacteria invading the blood` stream by agar diffusion method. The synthesized AgNPs show the ability to discourage the growth of the tested bacteria, which show high activities against most of the tested isolate of G + ve bacteria and G - ve bacteria that invading the blood stream. The current approach described rapid synthesis of silver using NaBH4 and PVP as reducing and stabilizing agents, respectively. This would be suitable for developing a process for discouraging the pathogenic bacteria activities. (Received March 2, 2015; Accepted April 20, 2015) Keywords: Silver nanoparticles, Synthesis, Gram-positive, Gram-negative, Blood stream, Bacteria 1. Introduction The application of nanoscale materials and structures, usually ranging from 1 to 100 nanometers (nm), is an emerging area of nanoscience and nanotechnology, which provide solutions to technological and environmental challenges in many areas [1-2]. The chemical reduction methods are involved in the preparation of silver nanoparticles with well-controlled size in which silver ions are reduced by reductants and stabilizing or protecting agents to prevent these nanoparticles from agglomeration [3-4]. The new approach for the functional silver nanoparticles can be used as agents for the selective killing of pathogenic bacteria, however, topical silver have gained popularity once again, principally in the management of open wounds [5].There are many theories on the mechanism of anti-bacterial action of silver nanoparticles. It is widely believed that silver nanoparticles penetrate into the bacterial cell membrane, causing leakage and removal of intracellular material, ultimately causing bacteria death. It has also been reported that the impact * Corresponding author: mawad@ksu.edu.sa