Antimicrobial activity of spherical silver nanoparticles prepared using a biocompatible macromolecular capping agent: evidence for induction of a greatly prolonged bacterial lag phase

Background  

We have evaluated the antimicrobial properties of Ag-based nanoparticles (Nps) using two solid phase bioassays and found that 10-20 μL of 0.3-3 μM keratin-stabilized Nps (depending on the starting bacterial concentration = C _I) completely inhibited the growth of an equivalent volume of ca. 10³ to 10⁴ colony forming units per mL (CFU mL^-1) Staphylococcus aureus, Salmonella Typhimurium, or Escherichia coli O157:H7 on solid surfaces. Even after one week at 37°C on solid media, no growth was observed. At lower Np concentrations (= [Np]s), visible colonies were observed but they eventually ceased growing.