Design Principles of Bioresorbable Polymeric Scaffolds

Kossuth, Mary Beth; Perkins, Laura; Rapoza, Richard

doi:10.1016/j.iccl.2016.02.004

Cited by 17 publications

(16 citation statements)

References 29 publications

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“…PLLA is the first clinically approved polymeric material to manufacture Bioresorbable Vascular Scaffolds (BVSs) (2011-CE Mark, 2016-FDA) [2,3], a medical implant that aims at replacing metal stents in the treatment of Coronary Heart Disease (CHD) [4]. One of the limitations of PLLA based-BVSs is their thickness (about 150μm), still twice as thick than metal stents, due to intrinsic brittleness of the polymer.…”

Section: Introductionmentioning

confidence: 99%

Effect of tungsten disulfide (WS2) nanotubes on structural, morphological and mechanical properties of poly(L-lactide) (PLLA) films

Tammaro

Luccio

Borriello

et al. 2018

AIP Conference Proceedings

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Poly(L-lactide) (PLLA) is a semicrystalline, biocompatible and biodegradable polymer widely employed in many applications (food packaging, biomedical devices, drug delivery systems). This work deals with nanocomposites of PLLA and tungsten disulfide (WS 2 ) nanotubes (NTs) as a novel material to obtain thinner and stronger bioresorbable vascular scaffolds. We studied the influence of WS 2 NTs on the mechanical properties of PLLA-WS 2 films. Polarized optical microscopy reveals a high degree of orientation of the polymer molecules in stretched films that further increases with a post-stretching annealing treatment. At the same time, X-ray diffraction (XRD) and Raman spectroscopy confirm enhancement of the crystallinity induced by the WS 2 NTs.

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Section: Introductionmentioning

confidence: 99%

Effect of tungsten disulfide (WS2) nanotubes on structural, morphological and mechanical properties of poly(L-lactide) (PLLA) films

Tammaro

Luccio

Borriello

et al. 2018

AIP Conference Proceedings

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“…PLLA preforms can be expanded to a thickness comparable to that of permanent stents (∼80 μm), but they must be strong enough to resists vessel spasms (∼300 mm Hg) (12) to support the occluded artery. Concerns regarding faster degradation of thinner scaffolds are mitigated by the fact that there is negligible mass loss at 12 mo for current BVSs-twice the time required for supporting the artery (38). A thinner scaffold is expected to relieve the compression of the inner bend during crimping and reduce the out-of-plane strain; thus, the present results suggest that thinner scaffolds will have proportionately smaller diamond-shaped voids.…”

Section: Discussionmentioning

confidence: 78%

“…Scaffolds must not fracture even if overdilated during implantation and must retain their strength for 6 mo (38) to support the occluded artery. The requirement of lasting strength is the compelling advantage of pure PLLA relative to more ductile PLLA blends or copolymers.…”

Section: Discussionmentioning

confidence: 99%

Multiplicity of morphologies in poly ( l -lactide) bioresorbable vascular scaffolds

Ailianou

Ramachandran

Kossuth³

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Poly(L-lactide) (PLLA) is the structural material of the first clinically approved bioresorbable vascular scaffold (BVS), a promising alternative to permanent metal stents for treatment of coronary heart disease. BVSs are transient implants that support the occluded artery for 6 mo and are completely resorbed in 2 y. Clinical trials of BVSs report restoration of arterial vasomotion and elimination of serious complications such as late stent thrombosis. It is remarkable that a scaffold made from PLLA, known as a brittle polymer, does not fracture when crimped onto a balloon catheter or during deployment in the artery. We used X-ray microdiffraction to discover how PLLA acquired ductile character and found that the crimping process creates localized regions of extreme anisotropy; PLLA chains in the scaffold change orientation from the hoop direction to the radial direction on micrometer-scale distances. This multiplicity of morphologies in the crimped scaffold works in tandem to enable a low-stress response during deployment, which avoids fracture of the PLLA hoops and leaves them with the strength needed to support the artery. Thus, the transformations of the semicrystalline PLLA microstructure during crimping explain the unexpected strength and ductility of the current BVS and point the way to thinner resorbable scaffolds in the future. structural transformation | ductility | poly (L-lactide) | coronary heart disease | microdiffraction C ardiovascular disease (CVD) claims over 15 million lives per year-more lives than communicable, maternal, neonatal, and nutritional disorders combined and more than twice the number of deaths due to all cancers (1). Coronary heart disease (CHD), the narrowing of coronary arteries due to the deposition of plaque, accounts for nearly 50% of all CVD deaths (1). To restore blood flow, most patients receive minimally invasive balloon angioplasty followed by stent implantation (1 million in 2008 in the United States) (2). Stents are metal mesh tubes that are delivered to the target lesion while they are crimped onto a balloon. Once they are positioned at the lesion, inflation of the balloon compresses the plaque against the vessel wall and deploys the stent to provide support at the enlarged diameter after the balloon is deflated and withdrawn. Metal stents are permanent, and their stiffness prohibits vasomotion and dilation (3, 4). Further, they present a lifelong risk of late stent thrombosis (3-6). A new technology is poised to displace metal stents: bioresorbable vascular scaffolds (BVS), which have been deemed the "fourth revolution" in percutaneous coronary intervention (7,8).The goal of tissue scaffolds is to restore the healthy state of the tissue, rather than merely ameliorating the diseased state (9-11). Poly(L-lactide) (PLLA) was selected as the material for BVS because its semicrystalline structure gives it adequate radial strength [>300 mm Hg (12)], and it degrades into products that are metabolized by the human body (13-16). Clinically, bioresorption of PLLA vascular sca...

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“…The results presented here are related to local material volumes of lased scaffolds and do not represent the overall bulk material properties of a finished scaffold. Previously, evaluation of finished product mechanical performance (radial strength) of BVS has indicated qualitative changes in the load response without a reduction in strength at 12 months degradation . Taken together, these results indicate that even with changes in local mechanical properties due to degradation, the bulk mechanical strength can still be maintained.…”

Section: Resultsmentioning

confidence: 99%

Quantifying the mechanical properties of polymeric tubing and scaffold using atomic force microscopy and nanoindentation

Naseem

Zhao

Silberschmidt

et al. 2019

Polymer Engineering & Sci

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Measurement of mechanical parameters of polymeric scaffolds presents a significant challenge due to their intricate shape and small characteristics dimensions of their elements—around 100 μm. In this study, mechanical properties of polymeric tubing and scaffold, made of biodegradable poly(l‐lactic) acid (PLLA), were characterized using atomic force microscopy (AFM) and nanoindentation, complemented with tensile testing. AFM was employed to assess the properties of the tube and scaffold locally, while nanoindentation produced results with a dependency on the depth of indentation. As a result, the AFM‐measured elastic modulus differs from the nanoindentation data due to a substantial difference in indentation depth between the two methods. With AFM, a modulus between 2 and 2.5 GPa was measured, while a wide range was obtained from nanoindentation on both the tube and scaffold, depending on the indentation scale. Changes in the elastic modulus with in‐vitro degradation and aging were observed over the 1‐year period. To complement the indentation measurements, tensile testing was used to study the structural behavior of the tube, demonstrating the yielding, hardening and fracture properties of the material. POLYM. ENG. SCI., 59:1084–1091, 2019. © 2019 Society of Plastics Engineers

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Design Principles of Bioresorbable Polymeric Scaffolds

Cited by 17 publications

References 29 publications

Effect of tungsten disulfide (WS2) nanotubes on structural, morphological and mechanical properties of poly(L-lactide) (PLLA) films

Effect of tungsten disulfide (WS2) nanotubes on structural, morphological and mechanical properties of poly(L-lactide) (PLLA) films

Multiplicity of morphologies in poly ( l -lactide) bioresorbable vascular scaffolds

Quantifying the mechanical properties of polymeric tubing and scaffold using atomic force microscopy and nanoindentation

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