title: Huge increase of therapeutic window at a bioactive silver/titania nanocomposite coating surface compared to solution.
abstract: A silver containing coating used in the human body, e.g., on an implant should be both effectively antimicrobial and non-cytotoxic to human cells. It is generally believed that the biologic effect originates from silver ions released from the coating. Nanocomposites with well controlled Ag filling factor were prepared by co-sputtering, and the silver surface concentration and the silver release were determined by XPS and ICP-MS, respectively. Here we show that only a small therapeutic window exists for dissolved silver but the therapeutic window is largely increased at the surface. While the toxicity observed for mammalian cells in contact with the bioactive Ag/TiO2 nanocomposite surface and for silver ions in solution is rather similar the antimicrobial activity is drastically enhanced at the surface. A model is proposed to explain the strong increase of the antimicrobial activity at the surface. The present results not only question well-established tests for antimicrobial activity but they are also important for the design of antimicrobial coatings, e.g., for biomedical devices.
authors.affiliation: Institute for Materials Science - Multicomponent Materials, Christian-Albrechts University at Kiel, Kaiserstr. 2, 24143 Kiel, Germany.
authors.forename: Tomislav
authors.initials: T
authors.lastname: Hrkac
authors.forename: Claudia
authors.initials: C
authors.lastname: Röhl
authors.forename: Rainer
authors.initials: R
authors.lastname: Podschun
authors.forename: Vladimir
authors.initials: V
authors.lastname: Zaporojtchenko
authors.forename: Thomas
authors.initials: T
authors.lastname: Strunskus
authors.forename: Heike
authors.initials: H
authors.lastname: Papavlassopoulos
authors.forename: Dieter
authors.initials: D
authors.lastname: Garbe-Schönberg
authors.forename: Franz
authors.initials: F
authors.lastname: Faupel
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001422:Bacterial Adhesion / Q000187:drug effects; D002452:Cell Count; D016923:Cell Death / Q000187:drug effects; D020099:Coated Materials, Biocompatible / Q000494:pharmacology*; D020405:Dermis / Q000166:cytology; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D008826:Microbial Sensitivity Tests; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure; D056951:Photoelectron Spectroscopy; D012834:Silver / Q000494:pharmacology*; D012835:Silver Nitrate / Q000494:pharmacology; D012996:Solutions; D013054:Spectrophotometry, Atomic; D014025:Titanium / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D020099:Coated Materials, Biocompatible; D012996:Solutions; D049452:Green Fluorescent Proteins; C009495:titanium dioxide; D012834:Silver; D012835:Silver Nitrate; D014025:Titanium