No abstract

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.

A critical component of tissue engineering is the ability to functionally replace native tissue stroma. Electrospinning is a technique capable of forming fibrous constructs with a high surface area for increased cell−material interaction and enhanced biocompatibility. However, physical and biological properties of electrospun scaffolds are limited by design controllability on a macroscale. We developed a methodology for generating electrospun scaffolds with defined patterns and topographic features to influence physical properties and biological interactions. Five unique design electrospinning target collectors were fabricated to allow for generation of defined polymeric scaffold patterns including lines, sinusoids, squares, zigzags, and solid. Poly(lacticco-glycolic) acid was electrospun under identical conditions utilizing these varied targets, and constructs generated were examined as to their physical configuration, mechanical and chemical properties, and their ability to foster vascular smooth muscle cell adhesion and retention at 24 h. Modifying collector designs led to significant differences in fiber target coverage ranging from 300 mm 2 for solid (100% of the target area) to 217.8 mm 2 for lines (72.6% of the target area). Measured fiber excess, residual open area, and contact angle (hydrophobicity) followed the same trend as fiber target coverage with respect to the collector pattern: lines > sinusoids > squares > zigzags > solid. Similarly, the line design allowed for the greatest cell adhesion and retention (258 ± 31 cells), whereas solid exhibited the lowest (150 ± 15 cells); p < 0.05. There was a strong direct correlation of cell adhesion to construct residual open area (R 2 = 0.94), normalized fiber excess (R 2 = 0.99), and fiber grammage (R 2 = 0.72), with an inverse relationship to fiber target coverage (R 2 = 0.94). Our results demonstrate the ability to utilize patterned collectors for modifying macroscopic and microscopic electrospun scaffold features, which directly impact cell adhesion and retention, offering translational utility for designing specific tissue constructs.