title: Comparison of silver nanoparticles stored under air or argon with respect to the induction of intracellular free radicals and toxic effects toward keratinocytes.
abstract: Bacterial infections decreased considerably after the discovery of antibiotics. Nevertheless, because of the rising rate of infections caused by antibiotic-resistant bacteria strains, the search for new bactericidal agents has again become a crucial topic in clinical medicine. Silver nanoparticles (AgNP) have a huge potential in dermatology and wound care management because of their ability to release silver ions (Ag(+) ions) in a prolonged and sustained way. However, negative effects of silver on the patient's cells should not be underestimated. Furthermore, it has been controversially discussed whether AgNP are responsible for nanoparticle-specific outcomes or not. In this study, we investigated the effects of AgNP on human skin keratinocytes (HaCaT) in order to better understand the mechanisms of cytotoxicity and to improve the use of this highly reactive biocide in wound healing. We found that most of the cells with internalized AgNP displayed the typical morphological signs of apoptosis. The cell viability assay (XTT) showed concentration-dependent toxic effects of the AgNP toward HaCaT cells. The generation of reactive oxygen species (ROS) induced by AgNP was investigated in cell suspensions by means of electron paramagnetic resonance (EPR) spectroscopy. In order to distinguish between the effects of Ag(+) ions released during AgNP storage and those of Ag(+) ions released after nanoparticle application, we compared AgNP stored under air (O2) with AgNP stored under argon (Ar). Dispersions of AgNP stored under Ar have a low content of Ag(+) ions because of the absence of oxygen which is needed for oxidative dissolution. The results show that Ag(+) ions released during particle storage are responsible for most of the ROS produced during 1h incubation with the cells. AgNP (Ar) also induced intracellular ROS but to a much smaller extent compared to AgNP (O2). These findings highlight the complexity of experiments to assess the toxicity of AgNP and suggest the possibility of reducing AgNP toxic effects by storing AgNP formulations and even silver-containing wound dressing under an inert gas atmosphere.
authors.affiliation: Department of Dermatology, Venerology and Allergology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Ahlberg
authors.affiliation: Department of Dermatology, Venerology and Allergology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Martina C
authors.initials: MC
authors.lastname: Meinke
authors.affiliation: Department of Dermatology, Venerology and Allergology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Luise
authors.initials: L
authors.lastname: Werner
authors.affiliation: Inorganic Chemistry and Center for Nanointegration Duisburg-Essen (CeNIDE), University of Duisburg-Essen, Essen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Epple
authors.affiliation: Inorganic Chemistry and Center for Nanointegration Duisburg-Essen (CeNIDE), University of Duisburg-Essen, Essen, Germany.
authors.forename: Joerg
authors.initials: J
authors.lastname: Diendorf
authors.affiliation: Department of Dermatology, Venerology and Allergology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Blume-Peytavi
authors.affiliation: Department of Dermatology, Venerology and Allergology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Juergen
authors.initials: J
authors.lastname: Lademann
authors.affiliation: Department of Dermatology, Venerology and Allergology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Annika
authors.initials: A
authors.lastname: Vogt
authors.affiliation: Department of Dermatology, Venerology and Allergology, Charité - Universitätsmedizin Berlin, Berlin, Germany. Electronic address: fiorenza.rancan@charite.de.
authors.forename: Fiorenza
authors.initials: F
authors.lastname: Rancan
mesh_terms: D000388:Air; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000493:pharmacokinetics / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects; D001128:Argon / Q000737:chemistry*; D018929:Cell Culture Techniques; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004356:Drug Storage / Q000379:methods; D005609:Free Radicals / Q000378:metabolism*; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D053768:Metal Nanoparticles / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D010316:Particle Size; D012834:Silver / Q000737:chemistry / Q000493:pharmacokinetics / Q000633:toxicity*
chemical_list: D000900:Anti-Bacterial Agents; D005609:Free Radicals; D012834:Silver; D001128:Argon
keywords: AgNP; Cellular uptake; Cytotoxity; Electron paramagnetic resonance spectroscopy; Keratinocytes; Nanoparticles; Skin