Plastically Deformable, Mechanically Strong, and Degradable Polymeric Airway Stents from Sustainable Aliphatic Polyester Block Polymers.

Abstract

Airway stenting is an effective method for providing immediate relief from obstructions in tracheobronchial lumens. Standard airway stents made of silicone or metal have morbidities that motivate a transition to bioresorbable stents. Here, we reported a mechanically stiff and tough airway stent prepared from "LML" triblock copolymers featuring two polyesters, poly(l-lactide) (PLLA, "L") and poly(γ-methyl-ε-caprolactone) (PγMCL, "M"). The LMLs could be thermally processed in the melt and transitioned from Newtonian to shear thinning viscosity behavior with increasing molar mass. By tuning molar mass, we optimized the viscosity profile for extrusion-based 3D printing, achieving high-resolution fabrication of solid and open-cell stents without significant sagging or delamination. We also report a new stent deployment strategy using radial dilation of LML stents to induce plastic deformation. Mechanical testing indicated that intermediate molar mass stents could plastically deform during balloon dilation, achieving robust postdeployment structural integrity. Prestretched tensile specimens, emulating balloon-dilated samples, exhibited enhanced tensile strength and toughness in poststretched samples, critical for maintaining stent shape under physiological conditions. In situ SAXS/WAXS revealed contributions from PγMCL domain deformation and PLLA crystal fragmentation to the shape retention and toughness of plastically deformed samples. We validated this new strategy in vivo, successfully deploying an LML stent in a human-mimetic porcine lumen. Finally, through an in vitro cytotoxicity assay with primary human airway epithelial cells, along with the degradation study in a buffer solution at 37 °C, we established the cytocompatibility and biodegradability of the LMLs over long time periods, making them promising candidates for future customizable 3D-printed airway stents with superior mechanical performance, printability, cytocompatibility, and biodegradability.