title: Toxicity and antibacterial assessment of chitosan-coated silver nanoparticles on human pathogens and macrophage cells.
abstract: BACKGROUND
  Pathogenic bacteria are able to develop various strategies to counteract the bactericidal action of antibiotics. Silver nanoparticles (AgNPs) have emerged as a potential alternative to conventional antibiotics because of their potent antimicrobial properties. The purpose of this study was to synthesize chitosan-stabilized AgNPs (CS-AgNPs) and test for their cytotoxic, genotoxic, macrophage cell uptake, antibacterial, and antibiofilm activities.
  
  
  METHODS
  AgNPs were synthesized using chitosan as both a stabilizing and a reducing agent. Antibacterial activity was determined by colony-forming unit assay and scanning electron microscopy. Genotoxic and cytotoxic activity were determined by DNA fragmentation, comet, and MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assays. Cellular uptake and intracellular antibacterial activity were tested on macrophages.
  
  
  RESULTS
  CS-AgNPs exhibited potent antibacterial activity against different human pathogens and also impeded bacterial biofilm formation. Scanning electron microscopy analysis indicated that CS-AgNPs kill bacteria by disrupting the cell membrane. CS-AgNPs showed no significant cytotoxic or DNA damage effect on macrophages at the bactericidal dose. Propidium iodide staining indicated active endocytosis of CS-AgNPs resulting in reduced intracellular bacterial survival in macrophages.
  
  
  CONCLUSIONS
  The present study concludes that at a specific dose, chitosan-based AgNPs kill bacteria without harming the host cells, thus representing a potential template for the design of antibacterial agents to decrease bacterial colonization and to overcome the problem of drug resistance.
authors.affiliation: School of Biotechnology, KIIT University, Bhubaneswar, Orissa, India.
authors.forename: Prajna
authors.initials: P
authors.lastname: Jena
authors.forename: Soumitra
authors.initials: S
authors.lastname: Mohanty
authors.forename: Rojee
authors.initials: R
authors.lastname: Mallick
authors.forename: Biju
authors.initials: B
authors.lastname: Jacob
authors.forename: Avinash
authors.initials: A
authors.lastname: Sonawane
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000737:chemistry; D001419:Bacteria / Q000187:drug effects* / Q000472:pathogenicity; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development; D002460:Cell Line; D048271:Chitosan / Q000737:chemistry; D004249:DNA Damage; D006801:Humans; D008264:Macrophages / Q000187:drug effects* / Q000382:microbiology; D053768:Metal Nanoparticles / Q000008:administration & dosage* / Q000737:chemistry / Q000633:toxicity; D051379:Mice; D008855:Microscopy, Electron, Scanning; D020102:Mycobacterium smegmatis / Q000187:drug effects; D053761:Nanocomposites / Q000008:administration & dosage / Q000737:chemistry / Q000633:toxicity; D050997:Nanomedicine; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D012485:Salmonella typhi / Q000187:drug effects; D012834:Silver / Q000737:chemistry / Q000633:toxicity; D013211:Staphylococcus aureus / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D012834:Silver; D048271:Chitosan