Impact of Tungsten Disulfide Nanotubes on the crystallization of poly(l-lactide) for thinner and stronger bioresorbable vascular scaffolds (BVS)

Bioresorbable Vascular Scaffolds (BVSs) are transient implants that can revolutionize the treatment of coronary heart disease by restoring vasomotion in the occluded artery. However, the adoption of pure poly L-lactide (PLLA) BVSs is hindered by their thickness (150µm), which is nearly twice that of metal stents. A thinner scaffold is easier to implant and can treat smaller lesions. A BVS reinforced with biocompatible Tungsten Disulfide (WS2) nanotubes (WSNTs) offers a solution towards a thinner, stronger BVS. To understand the impact of WSNTs on PLLA during processing, we subject PLLA and PLLA-WS2 (0.05wt%, 0.1wt%) to a shear pulse and probe the evolution of birefringence in real time. We discovered that WSNTs favor the formation of “shish-kebabs” in PLLA. Thread-like precursors that grow into shish are characterized by an upturn in birefringence during flow and kebabs are detected by an increase in birefringence after cessation of flow. Intriguingly, PLLA and PLLA-WS2 (0.05%) lack an oriented skin along the flow-direction, but possess a skin normal to the flow-direction. However, PLLA-WS2 (0.1%) exhibits a skin along both directions. We are investigating further upon this unexpected morphology and the role of WSNTs in enabling a thinner, stronger BVS.