Biocompatibility is the ability of a material or device to perform its intended function without causing an unacceptable adverse local or systemic biological response in the body. It is a property of the whole system in a specific context of use rather than an intrinsic property of a material: a polymer that is entirely safe as an external housing may be unacceptable as a long-term implant.
The governing framework is the ISO 10993 series, with ISO 10993-1 setting out the overall evaluation approach within a risk management process. That framing matters. The standard does not present a fixed checklist of tests to run; it requires a documented biological evaluation that identifies what is already known, what remains uncertain and what testing is genuinely needed to resolve it.
Evaluation begins with categorising the device by the nature of body contact (surface contact, external communicating or implant) and by contact duration (limited, up to 24 hours; prolonged, up to 30 days; long term, beyond 30 days). Those two axes determine which biological endpoints require consideration.
Regulatory expectations have shifted towards chemical characterisation, under ISO 10993-18, as a first step. Identifying extractables and leachables and assessing them against toxicological thresholds can answer many questions without animal testing, and supports the widely accepted principle of reducing, refining and replacing animal studies. Manufacturers must also control changes: a new supplier, resin grade, colourant or sterilisation method can invalidate an existing biological evaluation.
.svg)
