Hemocompatibility of polymers for use in vascular endoluminal implants

Implanted polymers for cardiovascular applications may function as structural supports, barriers, or provide a means for local drug delivery. Several thermoplastic biodegradable drug delivery polymers are potential candidates for blood-contacting implant applications. For intravascular applications specifically, a criterion for material selection is the intrinsic hemocompatibility of the baseline polymer. As an initial screening approach for selection of polymers for in vivo use, thin films of polyesters: poly(ɛ-caprolactone) (PCL), poly(lactic acid) (PLA), poly(lactic-co-glycolic acid) (PLGA); polyanhydrides: poly(fatty acid dimer-co-sebacic acid) (PFAD:SA) and poly(biscarboxyphenoxypropane-co-sebacic acid) (PCPP:SA); and poly(ethylene glycol) (PEG)-ylated polyesters: PLA:PEG, PCL:PEG and PCL:PLA:PEG polymers were spin-cast on glass cover slips and placed in an in vitro flow system exposing them at a controlled shear to overflowing human whole blood. Platelet adherence, aggregate formation, and thrombus formation, as well as leukocyte adherence were assessed following 5 min of flow. At 5 min of flow the rank order of materials, in terms of least to most thrombogenic was: PCL < PFAD:SA < PCPP:SA < PLGA < PLA. All PEGylated materials, in general, had less thrombus formation than baseline unmodified materials.