First, the physicochemical profile of a material defines that material and provides information about the quantities and identities of any extractables it may contain. Materials that possess large amounts of extractables are not necessarily toxic to a patient under clinical-use conditions. Much depends on the nature of the extractables and the amount of the material used in the device. However, extractable-rich materials should be considered suspect until shown to be biocompatible. Second, the characterization profile of a material identifies the material at the time samples were subjected to biocompatibility testing and thus provides the basis for specifications used to control the material's uniformity throughout a device's lifetime.
Adhesives require special consideration.
In their liquid or semiliquid form, many adhesives are relatively toxic. This usually changes for the better once they are polymerized. However, incompletely or improperly cured adhesives may contain residual quantities of starting materials, which can alter biocompatibility even from batch to batch. In this case, characterization is of particular importance to ensure that curing occurs as it was intended and as it did when samples were evaluated for biocompatibility. A variety of manufacturers offer electrically conductive adhesives with a range of applications and intended uses.