Electrospun vascular graft properties following femtosecond laser ablation

Abstract

For polymers in tissue engineering to reach their full potential, the three-dimensional integration of cells with scaffolds must become more complex. In vascular grafts this is particularly challenging as specific physical property requirements must be met. We apply a combination of polymer processing techniques-electrospinning and femtosecond laser ablation-to produce microchannels inside the walls of electrospun tubes providing for spatially-controlled cell seeding. To determine if such a scaffold can provide the desired physical properties, a greater understanding of the relationship between manufacturing and mechanics is needed. As the strength of these scaffolds is an important functional component, the relative properties of single, bi-and tri-layer combinations produced using different solvents were compared.The effect of fiber layer thickness was also investigated. The thickness of the hexafluorisopropanol-derived layer dominated the overall scaffold properties regardless of the nature of the other two layers. Although laser-machined microchannels had substantial effects on single layer and some of the bilayers, in the ''final'' trilayer scaffold, little effect on mechanical properties was observed. The concept of ''vascular wall engineering'' could successfully produce trilayer composite scaffolds that maintain the targeted mechanical properties while allowing intricate, three-dimensional cell seeding.

Vascular Wall Engineering Via Femtosecond Laser Ablation: Scaffolds with Self-Containing Smooth Muscle Cell Populations

“…35,41 Thus, the scaffold was fabricated using only one polymer-PCL-because of its well-known biocompatibility, slow degradation rate, 51 ease of electrospinning, 30,45 and mechanical capabilities in electrospun form. 5,13,19 In addition to promoting cell adhesion and maintaining viability, scaffolds for engineered blood vessels must promote proper cell organization and orientation, especially in the tunica media of the vessel. Healthy smooth muscle cells exhibit a spindle-like morphology and are oriented in a helical pattern around the vessels causing blood to be pumped through the vessel each time the smooth muscle cells contract.…”

“…We have previously shown that a thick-enough layer of fiber spun from HFP can successfully compensate for the presence of laser-ablated porosity. 19 Seeding of representative cell populations-both endothelial cells (ECs) and smooth muscle cells (SMCs)-should modulate the thrombogenicity of the endothelial layer by covering the synthetic luminal surface with adherent endothelial cells. 12,20 Signaling between these cell populations plays a significant role in blood vessel function.…”

“…If designed correctly, then this tri-layered structure can include microchannels that do not compromise the overall mechanical properties. 19 However, the ability of these tri-layered scaffolds to promote cell attachment, viability, and organization has not been investigated.…”

“…5 In a prior study, direct-write femtosecond laser ablation was employed to create a series of microchannels (100 lm deep, 100 lm wide, and 1.6 mm long) running the length of tri-layered 3D electrospun scaffolds. 19 The tri-layer scaffold was composed of a low-porosity electrospun fiber layer creating a surface for endothelial cell attachment (tunica intima), a high-porosity fiber layer containing femtosecond laser-ablated microchannels that facilitate directed seeding, infiltration, and organization of smooth muscle cells (tunica media), and a mechanically robust electrospun fiber layer to provide appropriate mechanical strengths (tunica adventitia). If designed correctly, then this tri-layered structure can include microchannels that do not compromise the overall mechanical properties.…”

Effect of spatial arrangement and structure of hierarchically patterned fibrous scaffolds generated by a femtosecond laser on cardiomyoblast behavior

“…To overcome the weakness of these conventional fabrication methods used for fibrous scaffolds, the utilization of femtosecond laser processing has been attempted . The laser processing of materials offers several advantages such as a delicate patterning technique through a fast and uncomplicated process of direct ablation of the material .…”