Hemocompatibility of dialyzers or oxygenators (in vitro)
Dialysis und oxygenation membranes in extracorporeal circuits are in contact with heparinized patient blood which leads to interactions between blood and the material. Since many different medical devices come in contact with blood during their use, the methods developed in our laboratories for membranes have been applied to characterize biological safety of other, non-membrane containing medical devices.
Hemocompatibility is a major development goal and a prerequisite for approval of devices used in extracorporeal circuits such as hemodialyzers and blood oxygenators. Therefore, during development and finally release of products for clinical tests it is mandatory to perform careful and reliable hemocompatibility assessment as close as possible to the clinical application e.g. using the same device (lot) as during the clinical study.
We perform our pre-clinical tests in a simulated extracorporeal circuit using clinical sized modules and freshly donated, heparinized human blood. In our studies we recommend to compare hemocompatibility parameters of a newly developed membrane or device with products which are already approved and in clinical use. Thus, the results can easily be transferred to the clinical situation.
In our set-ups we can compare up to eight dialyzers and several oxygenators in parallel to assess the hemocompatibility according to ISO 10993-4 of
- Clinical size medical devices (about 0.2-2.5 m²)
- Miniaturised (down-scaled) devices (about 250 cm²)
- Polymer films or flat sheet membranes (about 10-25 cm²)
- Oxygenators
- Powders, suspensions etc.
Hemocompatibility parameters routinely measured in our laboratory include:
- sC5b-9, C3a, C5a (fragment of complement factor C5) as a read out of complement activation (ELISA)
- TAT (Thrombin/Antithrombin III complex) indicating activation of the clotting system (ELISA)
- Free hemoglobin as a paramater of damage of erythrocytes (hemolysis)
- Heparin consumption (anti factor Xa, chromogenic substrate assay)
- Platelet count as parameter of platelet activation (cell counter)
- Several methods for the measurement of redness caused by residual blood in the dialyzer (image analysis, Minolta Chromameter).
- CR3/CD62L (expression of adhesion receptors) to determine activation of neutrophils or other blood cells (flow-cytometry)
- Interleukin-1ß (cytokine release) as parameter of monocyte activation (ELISA) in order to test pyrogenicity of medical devices
In principle, analysis of any biochemical parameter is possible (see our directory of services). Please contact us if you do not find the parameter in question in our directory of services. However, it is our speciality and we are very interested to establish new parameters and methods within the scope of our biomedical expertise. (Research and Development)