Problems and artefacts in the evaluation of polymeric materials for medical uses

The terms 'biocompatibility', 'blood compatibility', and 'thrombogenicity' are often used interchangeably which leads to confusion in the scientific and medical literatures. No single test can reliably predict the 'blood compatibility' of materials, and tests for thrombogenicity are not necessarily indicators of blood compatibility. Although the toxicological screening of biomaterials is important, the absence of adverse effects does not assure biocompatibility. Acute toxicological screenings should be carried in the biological evaluation phases of biomaterials but the results should be interpreted with caution because polymers degrade in the physiological environment by time-dependent mechanisms leading to the formation of potentially toxic products, including carcinogens. Increased efforts are needed to screen potential biomaterials for carcinogenesis and mutagenesis. Biological tests should be conducted with animals whose haematological profile closely resembles that of humans rather than rely on results obtained wity species such as dogs and calves. Accelerated fatigue testing of elastomers must be conducted under condition that closely approximate the properties of the biological environment to avoid catastrophic failures.