Multiplicity of morphologies in poly (l-lactide) bioresorbable vascular scaffolds.
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.
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125.
Artemis
A
Ailianou
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125.
Karthik
K
Ramachandran
Bioresorbable Vascular Scaffold, Research & Development, Abbott Vascular, Santa Clara, CA 95054.
Mary Beth
MB
Kossuth
Bioresorbable Vascular Scaffold, Research & Development, Abbott Vascular, Santa Clara, CA 95054.
James Paul
JP
Oberhauser
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125; jakornfield@cheme.caltech.edu.
Julia A
JA
Kornfield
D020341:Absorbable Implants; D003324:Coronary Artery Disease / Q000628:therapy; D006801:Humans; D055595:Mechanical Phenomena; D008855:Microscopy, Electron, Scanning; D008859:Microscopy, Polarization; D011091:Polyesters / Q000737:chemistry; D054457:Tissue Scaffolds / Q000737:chemistry; D014961:X-Ray Diffraction
D011091:Polyesters; C033616:poly(lactide)
coronary heart disease; ductility; microdiffraction; poly (l-lactide); structural transformation
J Biomed Mater Res. 1999;48(3):342-53
10398040
Biomaterials. 2003 Apr;24(9):1613-20
12559821
J Am Coll Cardiol. 2003 Apr 16;41(8):1283-8
12706922
Biomaterials. 2003 Oct;24(23):4181-90
12853248
Nature. 2004 Apr 1;428(6982):487-92
15057821
Biomaterials. 1992;13(3):176-82
1567942
Biomaterials. 2005 Oct;26(29):5771-82
15949544
J Am Chem Soc. 2005 Jul 20;127(28):10096-100
16011375
Proc Natl Acad Sci U S A. 2006 Apr 18;103(16):6315-20
16606824
J Synchrotron Radiat. 1997 Jul 1;4(Pt 4):223-7
16699234
Lancet. 2007 Sep 15;370(9591):937-48
17869634
Lancet. 2008 Mar 15;371(9616):899-907
18342684
Int J Cardiovasc Imaging. 2012 Jan;28(1):51-8
21213050
Circulation. 2011 Feb 22;123(7):779-97
21343594
JAMA. 2011 May 4;305(17):1769-76
21540420
EuroIntervention. 2012 Apr;7(12):1461-3
21959101
EuroIntervention. 2009 Dec 15;5 Suppl F:F15-22
22100671
Science. 2011 Dec 2;334(6060):1234-9
22144618
Circ Cardiovasc Interv. 2012 Oct;5(5):620-32
23048057
ACS Appl Mater Interfaces. 2012 Dec;4(12):6774-84
23153180
Science. 2012 Nov 16;338(6109):921-6
23161993
Eur Heart J. 2014 Mar;35(12):765-76
24366915
Eur Heart J. 2014 Nov 7;35(42):2950-9
25139896
J Am Coll Cardiol. 2014 Dec 16;64(23):2541-51
25500240
Nat Rev Cardiol. 2015 Jun;12(6):325-36
25781415
Ann Biomed Eng. 2016 Feb;44(2):330-40
26369638
Proc Natl Acad Sci U S A. 2015 Nov 24;112(47):14444-51
26598696
Nature. 2016 Feb 4;530(7588):71-6
26779949
J Am Coll Cardiol. 2016 Feb 23;67(7):766-76
26892411
J Interv Cardiol. 2016 Oct;29(5):546-548
27492571
Interv Cardiol Clin. 2016 Jul;5(3):349-355
28582032