Evaluation of silver bio-functionality in a multicellular in vitro model: towards reduced animal usage in implant-associated infection research

Leonardo Cecotto; Daphne A C Stapels; Kok P M van Kessel; Michiel Croes; Zeldali Lourens; H Charles Vogely; Bart C H van der Wal; Jos A G van Strijp; Harrie Weinans; Saber Amin Yavari

doi:10.3389/fcimb.2023.1186936

Evaluation of silver bio-functionality in a multicellular in vitro model: towards reduced animal usage in implant-associated infection research

Front Cell Infect Microbiol. 2023 Jun 5:13:1186936. doi: 10.3389/fcimb.2023.1186936. eCollection 2023.

Authors

Affiliations

¹ Department of Orthopedics, University Medical Center Utrecht, Utrecht, Netherlands.
² Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, Netherlands.
³ Infection Biology Group, Department of Biomolecular Health Sciences, Utrecht University, Utrecht, Netherlands.
⁴ Department of Biomechanical Engineering, Delft University of Technology, Delft, Netherlands.
⁵ Regenerative Medicine Centre Utrecht, Utrecht University, Utrecht, Netherlands.

Abstract

Background: Despite the extensive use of silver ions or nanoparticles in research related to preventing implant-associated infections (IAI), their use in clinical practice has been debated. This is because the strong antibacterial properties of silver are counterbalanced by adverse effects on host cells. One of the reasons for this may be the lack of comprehensive in vitro models that are capable of analyzing host-bacteria and host-host interactions.

Methods and results: In this study, we tested silver efficacy through multicellular in vitro models involving macrophages (immune system), mesenchymal stem cells (MSCs, bone cells), and S. aureus (pathogen). Our model showed to be capable of identifying each element of culture as well as tracking the intracellular survival of bacteria. Furthermore, the model enabled to find a therapeutic window for silver ions (AgNO₃) and silver nanoparticles (AgNPs) where the viability of host cells was not compromised, and the antibacterial properties of silver were maintained. While AgNO₃ between 0.00017 and 0.017 µg/mL retained antibacterial properties, host cell viability was not affected. The multicellular model, however, demonstrated that those concentrations had no effect on the survival of S. aureus, inside or outside host cells. Similarly, treatment with 20 nm AgNPs did not influence the phagocytic and killing capacity of macrophages or prevent S. aureus from invading MSCs. Moreover, exposure to 100 nm AgNPs elicited an inflammatory response by host cells as detected by the increased production of TNF-α and IL-6. This was visible only when macrophages and MSCs were cultured together.

Conclusions: Multicellular in vitro models such as the one used here that simulate complex in vivo scenarios can be used to screen other therapeutic compounds or antibacterial biomaterials without the need to use animals.

Keywords: antimicrobial; biomaterial-related infection; co-culture; cytotoxicity; immune response.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Anti-Bacterial Agents / pharmacology
Bacteria
Metal Nanoparticles*
Microbial Sensitivity Tests
Silver* / pharmacology
Staphylococcus aureus

Substances

Silver
Anti-Bacterial Agents

Grants and funding

The collaboration project is cofounded by the PPP Allowance made available by Health~Holland, Top Sector Life Sciences & Health, to stimulate public-private partnerships. This research also received co-funding from the EU’s H2020 research and innovation program under Marie S. Curie cofund RESCUE grant agreement No 801540. This publication is also part of the project DARTBAC (with project number NWA.1292.19.354 of the research program NWA-ORC which is (partly) financed by the Dutch Research Council (NWO).