Vascular wall engineering via femtosecond laser ablation: Scaffolds with self-containing smooth muscle cell populations

For tissue-engineered vascular grafts to reach their full potential, three-dimensional (3D) cellular micro-integration will be necessary. In this study, we utilize femtosecond laser ablation to produce microchannels inside electrospun polycaprolactone (PCL) scaffolds. These microchannels potentially provide spatially controlled cell distributions approaching those observed in vivo. The ability of such laser-ablated microchannels to direct cell seeding was evaluated. The dimensions chosen were 100 μm wide, 100 μm deep and 10 mm long. Femtosecond laser ablation successfully produced these microchannels in the scaffolds without substantially altering the ∼900 nm diameter fibers. Flow within these microchannels was studied by injecting fluorescent polystyrene bead solutions. Direct measurement of bead motion yielded an inlet velocity of 2.78 cm s^-1. This was used for modeling two-dimensional (2D) flow using computational fluid dynamics to estimate flow profiles within the microchannel. Successful demonstrations of bead flow were followed by seeding of 500,000 human coronary artery smooth muscle cells (HCASMCs) in proliferative medium at a rate of ∼500 μL min^-1. Confocal microscopy and scanning electron microscopy confirmed that the HCASMCs were seeded down the full 10-mm length of the microchannel and stayed within its boundaries. Both nuclei and F-actin were observed within the seeded cells. The presence of F-actin filaments shows that the cells were adhered strongly to the scaffold and remained viable throughout the culture. The concept of "vascular wall engineering" producing intricate cell seeding through microchannels produced via femtosecond laser ablation was validated.