Flow-Induced Crystallization of Polylactide (PLA) and Tungsten Disulfide Nanotubes (WSNTs) for Bioresorbable Vascular Scaffolds.

Bioresorbable Vascular Scaffolds (BVSs) are temporary implants made from bioresorbable and biocompatible polylactide (PLA), designed to replace metal stents in treating coronary heart disease. However, their adoption is hindered by their thickness, nearly double that of metal stents.

Our approach aims to develop a thinner yet stronger BVS by enhancing the radial strength of PLA through shear flow experiments to promote oriented crystallization. We also incorporated tungsten disulfide nanotubes (WSNTs) to boost PLA crystallization for a thinner device.

In situ rheo-optical experiments showed that the presence of WSNTs favors the formation of thread-like precursors as demonstrated by a distinct upturn in the birefringence signal during flow. These precursors successively grow into shish-kebabs as detected by an increase in birefringence after flow stops. Ex situ polarized light micrographs confirm the expected skin-core morphology with evidence of effective nucleation by the WSNTs. Surprisingly, both PLA and PLA-WSNTs show enhanced birefringent skin when observed down the flow direction compared to along the flow direction. This intriguing result prompted further investigation via x-ray microdiffraction to examine changes of local morphology across the sample with shear parameters.