Abstract
Coronary Heart Disease (CHD) is one of the leading causes of death worldwide, claiming over seven million lives each year. Permanent metal stents, the current standard of care for CHD, inhibit arterial vasomotion and induce serious complications such as late stent thrombosis. Bioresorbable vascular scaffolds (BVSs) made from poly l-lactide (PLLA) overcome these complications by supporting the occluded artery for 3–6 months and then being completely resorbed in 2–3 years, leaving behind a healthy artery. The BVS that recently received clinical approval is, however, relatively thick (~150 µm, approximately twice as thick as metal stents ~80 µm). Thinner scaffolds would facilitate implantation and enable treatment of smaller arteries. The key to a thinner scaffold is careful control of the PLLA microstructure during processing to confer greater strength in a thinner profile. However, the rapid time scales of processing (~1 s) defy prediction due to a lack of structural information. Here, we present a custom-designed instrument that connects the strain-field imposed on PLLA during processing to in situ development of microstructure observed using synchrotron X-ray scattering. The connection between deformation, structure and strength enables processing–structure–property relationships to guide the design of thinner yet stronger BVSs.
Highlights
Coronary heart disease (CHD) results in obstructed blood flow to the heart due to the deposition of plaque on arterial walls
The choice of Infrared heating (IR) radiation motivates the use of borosilicate glass (Pyrex) for the mold as Pyrex is mostly transparent to IR wavelengths that are strongly absorbed by poly L-lactide (PLLA)
These two modes of operation were selected to isolate the impact of the expansion temperature (Te ) from that of the crystallization temperature (Tx ) on the morphology of the expanded tube; expansion in the first mode is triggered at a set mold temperature while expansion in the second mode is reliant on the material properties of the preform
Summary
Coronary heart disease (CHD) results in obstructed blood flow to the heart due to the deposition of plaque on arterial walls. It is one of the leading causes of death in the world and claims over seven million lives each year [1,2,3]. Bioresorbable vascular scaffolds (BVSs) are emerging as a promising alternative to permanent metal stents for the treatment of CHD. These devices are referred to as “scaffolds” as opposed to “stents” owing to their transient nature in the implanted artery. PLLA is notorious for being a brittle polymer [12,13], Polymers 2018, 10, 288; doi:10.3390/polym10030288 www.mdpi.com/journal/polymers
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