Polymers and nanocomposites to treat vascular disease without a trace

Abstract

A wave of bioresorbable devices are being introduced to treat vascular disease in the heart and limbs. Biodegradable semicryst. polymers provide the structural material of leading bioresorbable scaffolds (BRSs), a credit to innovative processing methods developed to achieve new combinations of strength, toughness and hydrolysis profiles. With Abbott Vascular, we discovered the key to resilient poly L-lactide (PLLA) lies in the interaction of two manufg. steps-tube expansion and crimping. X-ray microdiffraction revealed dramatic gradients of structure created during crimping slow hydrolysis precisely where stress is concd., preserving strength where it is needed most. Even after 9 mo of hydrolysis in vitro, despite a 40% decrease in PLLA mol. wt., the BRS retains its initial strength. Clin. complications motivate thinner devices that are visible in x-ray radiog. during and after implantation. Toward the goal of stronger, radiopaque, bioresorbable materials, we explore PLLA reinforcement by inorg. nanotubes (NT) with strong x-ray absorption, specifically, tungsten disulfide (WS2). The effects of WS2NT on PLLA crystn. reveal a new interaction between early processing steps in BRS manuf. (preform extrusion and tube expansion). Innovative processing methods developed by biomedical device manufacturers give PLLA resilience to survive crimping, deployment and months of hydrolysis, fueling optimism that scaffolds will support arteries' ability to heal, ultimately enabling recovery from vascular diseases without leaving a trace.

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