Blood compatibility of polypropylene surfaces in relation to the crystalline-amorphous microstructure

Blood-contacting properties of polypropylene surfaces with different crystalline states at the surface layer were examined in terms of plasma protein adsorption and changes in cytoplasmic free Ca²⁺ levels in platelets. Though the wettability of polypropylene surfaces was almost constantly independent from the surface layer crystallinity and interlamellar spacing, an increase in adhesiveness was observed with decreasing surface layer crystallinity and interlamellar spacing. It is suggested that the surface properties of the sheets varied in relation to the crystalline-amorphous microstructure. Minimum magnitudes in albumin and fibrinogen adsorption were observed on the polypropylene surface with a particular surface layer crystallinity (c. 55 wt%). A decrease in interlamellar spacing resulted in enhancing albumin adsorption and diminishing fibrinogen adsorption. Transient phenomena in plasma protein adsorption were observed on their surfaces with a plasma concentration. It is considered that the polypropylene surface with a particular crystalline-amorphous microstructure reduces the denaturation of adsorbed proteins. An increase in cytoplasmic free Ca²⁺ levels in platelets was prevented at the polypropylene surface with a surface layer crystallinity of 55 wt%: the particular crystalline-amorphous microstructure of such apolar surfaces as polypropylenes acts to reduce platelet activation. Thus, it is concluded that the blood compatibility of polypropylene surfaces is greatly improved by controlling a crystalline-amorphous microstructure at the surface layer.