Material effects in shear-induced hemolysis

A rotating-disk apparatus for shearing blood was employed to compare 22 materials for their tendency to cause hemolysis during standardized low-stress (130 dynes/cm2 maximum) laminar flow conditions. Rigid plastics, hydrogels, and carbons were among the materials tested. Time-independent ranking of the materials was possible for 75% of the data; these rankings correlated linearly (for polymers) with the critical surface tension gammac over the range 20--46 dyne/cm, with low gammac being associated with low hemolysis. Surface morphology was also found to influence hemolysis. Roughness in the 1--15 micron range had a distinct effect on hemolysis kinetics for polyethylene surfaces. This suggest that failure to find time-independence in 25% of the material rankings can be attributed to inadequate control of the roughness variable. It also emphasizes the importance of surface morphology, as well as surface chemistry, as a biocompatibility parameter.