An in vitro pyrogen safety test for immune-stimulating components on surfaces

Due to the discovery of novel surgical techniques and new materials medical devices are increasingly used. Contact of these biomaterials with human tissue or blood commonly leads to inflammation of varying degrees, sometimes resulting in severe health problems. Possible causes are limited biocompatibility or pyrogenic contamination of the material. We adapted the recently validated in vitro pyrogen test (IPT), based on human whole blood cytokine release, to test the safety of biomaterials. Human whole blood is brought into direct contact with the surface of the test material and the release of the pro-inflammatory cytokine IL-1β is measured. This procedure represents a human-relevant assay allowing the detection of pyrogens of different origins, e.g. Gram-negative (lipopolysaccharide, LPS) or Gram-positive (lipoteichoic acid, LTA), peptidoglycan (cell wall components of most bacteria) and fungal zymosan by direct material contact. The sensitivity of the test system allows a starting concentration of 10 pg/ml for LPS, 10 ng/ml for zymosan and 1 μg/ml for LTA and peptidoglycan from different strains. Furthermore, we have shown that the test for solid materials can be carried out with cryo-preserved blood, which results in an even lower detection limit.