A discussion of silver’s cytotoxicity with respect to the biological evaluation of a wound dressing

Client

An international manufacturer of wound care products.

Background

According to the results of an in vitro cytotoxicity assay, conducted in accordance with ISO 10993-5 guidelines, an extract of the client’s silver-containing wound dressing product demonstrated evidence of toxicity to mouse fibroblast cells.

Project goals

Bibra was asked to investigate the cytotoxic potential of silver, and to justify the incorporation of silver within the wound dressing in a biological evaluation report.

Approach

Although it is well recognised that silver is adopted in wound dressings for its antibacterial properties, cellular toxicity is a potentially serious side-effect that must be considered in a biological evaluation. Bibra discussed the cytotoxicity of silver, its mode-of-action and relevance to mammalian cells, as well as the clinical importance of silver. Furthermore, bibra evaluated the results of an in vivo wound healing study conducted with the wound dressing product to inform on the overall weight-of-evidence, and also considered the toxicity of the other component materials of the dressing.

Project outcome

It was concluded that, while a negative result in an in vitro cytotoxicity study is very reassuring, a positive result in this artificial test system is not necessarily indicative of a risk in actual use. Cytotoxicity potential was found to be of particular concern in regard to new cell growth (healing). If the healing process is unaffected by a treatment, then the observation of cytotoxicity in a highly sensitive 10993-5 test was considered to be of little or no practical consequence. In the wound healing study, no significant local reactions or impairment of wound healing was identified, compared to a suitable control. Overall, therefore, bibra was able to conclude that the silver-containing wound dressing was biocompatible, with respect to this endpoint.

Bibra project team

Charles Johnson
Pete Watts

 

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