Time-related contact angle measurements with human plasma on biomaterial surfaces

Axisymmetric drop shape analysis by profile (ADSA-P) was used to assess in time contact angle changes of human plasma drops placed on four different b iomaterials. Results were related with conventional blood compatibility mea surements: albumin adsorption, fibrinogen adsorption and platelet adhesion. While contact angle measurements with water are material-related but const ant in time, contact angle measurements with plasma changed over time owing to protein adsorption on the solid-liquid interface. The contact medium pl asma did not influence the initial contact angle. Contact angles on PDMS de creased most in time (41 degrees) and demonstrated highest levels of conven tionally measured albumin and fibrinogen adsorption and platelet adhesion. PTFE, with the lowest contact angle decrease over a 500 minutes period (19 degrees), showed low fibrinogen and albumin adsorption as well as low plate let adhesion. PU and HDPE demonstrated almost similar initial contact angle s with plasma and contact angle decreases (26 and 27 degrees), intermediate protein adsorption, and platelet adhesion. We conclude that biocompatibili ty properties of the tested materials may be more related to the behaviour of their contact angles in time, than to the initial hydrophobic or hydroph ilic state.