title: Antibacterial activity of optically transparent nanocomposite films based on chitosan or its derivatives and silver nanoparticles.
abstract: Colloidal silver nanoparticles (NPs) were prepared using the citrate and borohydride reduction methods and were then investigated as fillers in three matrices: unmodified chitosan, water-soluble chitosan and a N-alkyl chitosan derivative. The nanocomposites were used to prepare cast thin films (9-19 μm thickness) and characterized for their optical and antimicrobial properties. The optical properties of the materials were adjusted either by varying the Ag NPs content in the films (0.5-3.9% w/w) or by using samples of Ag NPs with distinct particle size distributions. The antibacterial activity towards both Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Klebsiella pneumoniae and Escherichia coli) was investigated for the various composites. For the unmodified chitosan nanocomposites, the bactericidal effect depended on their Ag content while such an effect was always observed for water-soluble chitosan and N-alkyl chitosan based materials. This research provides a basis for the evaluation of chitosan/silver composites in applications requiring flexible films with tuned optical properties and antimicrobial activity.
authors.affiliation: Department of Chemistry and CICECO, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Ricardo J B
authors.initials: RJ
authors.lastname: Pinto
authors.forename: Susana C M
authors.initials: SC
authors.lastname: Fernandes
authors.forename: Carmen S R
authors.initials: CS
authors.lastname: Freire
authors.forename: Patrizia
authors.initials: P
authors.lastname: Sadocco
authors.forename: Jessica
authors.initials: J
authors.lastname: Causio
authors.forename: Carlos Pascoal
authors.initials: CP
authors.lastname: Neto
authors.forename: Tito
authors.initials: T
authors.lastname: Trindade
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D048271:Chitosan / Q000737:chemistry / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects; D007711:Klebsiella pneumoniae / Q000187:drug effects; D053768:Metal Nanoparticles / Q000737:chemistry*; D008826:Microbial Sensitivity Tests; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure; D050997:Nanomedicine; D010316:Particle Size; D012834:Silver / Q000737:chemistry / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D012834:Silver; D048271:Chitosan