Therapeutic Window of Ligand-Free Silver Nanoparticles in Agar-Embedded and Colloidal State: In Vitro Bactericidal Effects and Cytotoxicity

Authors

  • Sebastian Grade,

    Corresponding author
    1. Department of Prosthetic Dentistry and Biomedical Materials Science, Carl-Neuberg-Straße 1, Hannover Medical School, 30625 Hannover, (Germany)
    • Department of Prosthetic Dentistry and Biomedical Materials Science, Hannover Medical School, Carl-Neuberg-Straße 1, 30625 Hannover, (Germany)
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  • Jörg Eberhard,

    1. Department of Prosthetic Dentistry and Biomedical Materials Science, Carl-Neuberg-Straße 1, Hannover Medical School, 30625 Hannover, (Germany)
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  • Philipp Wagener,

    1. Department of Materials and Processes, Laser Zentrum Hannover e.V, Hollerithallee 8, 30419 Hannover, (Germany)
    2. Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CeNIDE), University of Duisburg-Essen, Universitätsstraße 7, 45141 Essen, (Germany)
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  • Andreas Winkel,

    1. Department of Prosthetic Dentistry and Biomedical Materials Science, Carl-Neuberg-Straße 1, Hannover Medical School, 30625 Hannover, (Germany)
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  • Csaba Laszlo Sajti,

    1. Department of Materials and Processes, Laser Zentrum Hannover e.V, Hollerithallee 8, 30419 Hannover, (Germany)
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  • Stephan Barcikowski,

    1. Department of Materials and Processes, Laser Zentrum Hannover e.V, Hollerithallee 8, 30419 Hannover, (Germany)
    2. Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CeNIDE), University of Duisburg-Essen, Universitätsstraße 7, 45141 Essen, (Germany)
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  • Meike Stiesch

    1. Department of Prosthetic Dentistry and Biomedical Materials Science, Carl-Neuberg-Straße 1, Hannover Medical School, 30625 Hannover, (Germany)
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Abstract

The inhibition of bacterial growth through effective non-toxic antimicrobial substances is of great importance for the prevention and therapy of implant infections in various medical disciplines. For the evaluation of a therapeutic window of silver nanoparticles (AgNPs), their bactericidal properties were tested in agar composites and colloids on four medical relevant bacteria. Therefore, we produced AgNPs using high-power nanosecond laser ablation in water showing a log-normal particle diameter distribution centered at 17 nm. Bacteria were incubated with AgNP concentrations ranging from 5 to 70 µg · mL−1 and the growth rate was recorded. Additionally, cytotoxic effects of AgNPs on human gingival fibroblasts were examined. The experiments demonstrated that laser-synthesized AgNPs resulted in a significant bacterial growth inhibition of more than 80% at the indicated concentrations in a solid agar model (Pseudomonas aeruginosa 10 µg · mL−1, Streptococcus salivarius 10 µg · mL−1, Escherichia coli 20 µg · mL−1, Staphylococcus aureus 70 µg · mL−1). In a planktonic bacteria model, the growth of the tested bacteria was significantly delayed by the addition of AgNPs at a concentration of 35 µg · mL−1. The cytotoxic assays showed limited adverse effects on human fibroblasts at concentrations of less than 20 µg · mL−1. The present study illustrates the strong antibacterial effects of ligand-free, laser-generated AgNPs that exhibit moderate cytotoxic effects, resulting in a therapeutically applicable concentration of AgNPs for medical purposes between 10 and 20 µg · mL−1.

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