SYMPOSIA PAPER Published: 23 November 2020
STP163020190123

In Vitro Test Methods for Antimicrobial Coatings on Medical Devices: Learnings from Industry

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While developing antimicrobial coatings for orthopedic devices, it is necessary to have in vitro test methods that can assess and compare technologies or for quality control. Although there are existing standardized test methods for antimicrobial coatings, these methods are largely for applications other than medical devices. However, some do contain useful advice and practices. In this paper we share our experiences with existing test methods and present our own test methods. When considering the most suitable test method for a coating, it is necessary to understand the function of the coating. For example, is it designed to kill microbes around an implant (i.e., entering an already infected environment and seeking to treat the infection) or to prevent the colonization of an implant surface (and therefore biofilm generation and subsequent infection)? Other factors to keep in mind include the volume and composition of the media in which the test is being conducted. Microbiology testing typically utilizes specific growth/maintenance media (such as tryptone soya broth or maximum recovery diluent), but these solutions are designed to support bacterial growth rather than truly mimic the clinical environment. With this in mind, we have evaluated varying protein concentrations using our methods and have observed differences in minimum bactericidal concentration levels in a range of common antimicrobial compounds. Other factors to consider include the surface area of the implant and its intended location in the body. For example, the local environment of a tibial intramedullary nail is very different from that of a distal radius plate. Finally, one can decide to measure the number of microbes in the test suspension or the number adhered to the surface of the coated surface, or both. For in vivo testing, the model should ideally replicate the anatomy, biology, and geometry that the product will see in human clinical use.

Author Information

Rose, John
Smith & Nephew Inc., Cordova, TN, US
Vaughan, John
Smith & Nephew Ltd, Hull, GB
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Pages: 38–52
DOI: 10.1520/STP163020190123
ISBN-EB: 978-0-8031-7707-9
ISBN-13: 978-0-8031-7706-2