Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Antimicrobial activity of spherical silver nanoparticles prepared using a biocompatible macromolecular capping agent: evidence for induction of a greatly prolonged bacterial lag phase | Irwin et al. Journal of Nanobiotechnology 2010 8 34 http content 8 1 34 JOURNAL OF NANOBIOTECHNOLOGY RESEARCH Open Access Antimicrobial activity of spherical silver nanoparticles prepared using a biocompatible macromolecular capping agent evidence for induction of a greatly prolonged bacterial lag phase Peter Irwin1 Justin Martin1 2 Ly-Huong Nguyen1 Yiping He1 Andrew Gehring1 Chin-Yi Chen1 Abstract Background We have evaluated the antimicrobial properties of Ag-based nanoparticles Nps using two solid phase bioassays and found that 10-20 gL of gM keratin-stabilized Nps depending on the starting bacterial concentration CI 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. Results To further study the physiology of this growth inhibition we repeated these experiments in liquid phase by observing microbial growth via optical density at 590 nm OD at 37 C in the presence of a Np 0 to 10-6 M. To extract various growth parameters we fit all OD t data to a common sigmoidal function which provides measures of the beginning and final OD values a first-order rate constant k as well as the time to calculated 1 2-maximal OD tm which is a function of CI k as well as the microbiological lag time T . Performing such experiments using a 96-well microtitre plate reader we found that growth always occurred in solution but tm varied between 7 controls CI 8 X 103 CFU mL-1 and 20 hrs using either the citrate- Np 3 X 10-7 M or keratin-based Np 10-6 M Nps and observed that ctm a Np citrate 5 X 107 and ctm a Np keratin 107 hr-L mol-1. We also found that there was little effect of Nps on S. aureus growth rates which varied only between k and .
