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Influence of Thermal Annealing on the Mechanical Properties of PLLA Coiled Stents

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Abstract

To investigate the influence of elevated annealing temperature (70–90 °C) on the mechanical properties of coiled helical PLLA stents. PLLA 0.10 mm fibers and Ø3 mm × 12 mm stents were fabricated and annealed at 70, 80 and 90 °C for 25 min. The mechanical properties of the fibers and the functional characteristics of the stents were measured and compared to a control group processed at 21 °C. The stents were mounted, expanded and relaxed using an Ø3 mm × 2 cm balloon catheter to a maximum balloon pressure of 12 atm. Measurements of stent diameter, length, and the balloon pressure were used to determine the effective circumferential strain, incremental stiffness, elastic recoil, and lengthening of the stents. Stents exhibited progressively higher incremental stiffness with annealing temperature, higher collapse resistance and a reduction in elastic recoil vs. controls. Single fiber mechanical properties decreased as annealing temperature increased. Differential scanning calorimetry revealed crystallinity increased within thermally annealed stent fibers compared with controls. SEM examination indicated thermally annealed stents underwent less twisting than controls during balloon-induced unfurling. Thermal annealing of PLLA fibers and stents between 70 and 90 °C induced changes in crystalline structure, thereby favorably influencing fiber stress–strain behavior and stent expansion characteristics.

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Abbreviations

D 12 atm :

Stent diameter at a balloon pressure of 12 atm

D 0 atm :

Stent diameter when the balloon pressure is at 0 atm

D :

Instantaneous stent diameter at each pressure level

D 0 :

Stent diameter for the unfurled state

X c (%):

Percent crystallinity

References

  1. Barker G, Welch T, D’Souza N, Nugent A, Eberhart RC, editors. Influence of CO2 Blowing Agent on Porous Bioresorbable Stent Structure. ASME 2013 Summer Bioengineering Conference; 2013 June 26–29; Sunriver, Oregon, USA: ASME Proceedings.

  2. Drumright, R. E., P. R. Gruber, and D. E. Henton. Polylactic acid technology. Adv. Mater. 12:1841–1846, 2000.

    Article  Google Scholar 

  3. Engelberg, I., and J. Kohn. Physico-mechanical properties of degradable polymers used in medical applications: a comparative study. Biomaterials 12(3):292–304, 1991.

    Article  Google Scholar 

  4. Grabow, N., C. M. Bunger, C. Schultze, K. Schmohl, D. P. Martin, S. F. Williams, et al. A biodegradable slotted tube stent based on poly(L-lactide) and poly(4-hydroxybutyrate) for rapid balloon-expansion. Ann. Biomed. Eng. 35(12):2031–2038, 2007.

    Article  Google Scholar 

  5. Grabow, N., C. M. Bünger, K. Sternberg, S. Mews, K. Schmohl, and K.-P. Schmitz. Mechanical Properties of a Biodegradable Balloon-expandable Stent From Poly(L-lactide) for Peripheral Vascular Applications. J. Med. Devices 1(1):84–88, 2006.

    Article  Google Scholar 

  6. Grizzi, I., H. Garreau, S. Li, and M. Vert. Hydrolytic degradation of devices based on poly(DL-lactic acid) size-dependence. Biomaterials 16(4):305–311, 1995.

    Article  Google Scholar 

  7. Kotsar, A., T. Isotalo, I. Uurto, J. Mikkonen, P. Martikainen, M. Talja, et al. Urethral in situ biocompatibility of new drug-eluting biodegradable stents: an experimental study in the rabbit. BJU Int. 103(8):1132–1135, 2009.

    Article  Google Scholar 

  8. Levy, Y., D. Mandler, J. Weinberger, and A. J. Domb. Evaluation of drug-eluting stents’ coating durability–clinical and regulatory implications. J. Biomed. Mater. Res. B 91(1):441–451, 2009.

    Article  Google Scholar 

  9. Li, S. M., H. Garreau, and M. Vert. Structure-property relationships in the case of the degradation of massive aliphatic poly-(a-hydroxy acids) in aqueous media, Part 1: poly(DL-lactic acid). J. Mater. Sci.: Mater. Med. 1:123–130, 1990.

    Article  Google Scholar 

  10. Lincoff, A. M., J. G. Furst, S. G. Ellis, R. J. Tuch, and E. J. Topol. Sustained local delivery of dexamethasone by a novel intravascular eluting stent to prevent restenosis in the porcine coronary injury model. J. Am. Coll. Cardiol. 29(4):808–816, 1997.

    Article  Google Scholar 

  11. Mani, G., M. D. Feldman, D. Patel, and C. M. Agrawal. Coronary stents: a materials perspective. Biomaterials 28(9):1689–1710, 2007.

    Article  Google Scholar 

  12. Nishio, S., K. Kosuga, K. Igaki, M. Okada, E. Kyo, T. Tsuji, et al. Long-Term (>10 Years) clinical outcomes of first-in-human biodegradable poly-l-lactic acid coronary stents: Igaki-Tamai stents. Circulation 125(19):2343–2353, 2012.

    Article  Google Scholar 

  13. Oberhauser JP, Hossainy S, Rapoza RJ. Design principles and performance of bioresorbable polymeric vascular scaffolds. EuroIntervention : journal of EuroPCR in collaboration with the Working Group on Interventional Cardiology of the European Society of Cardiology. 2009;5 Suppl F:F15-22.

  14. Onuma, Y., and P. W. Serruys. Bioresorbable scaffold: the advent of a new era in percutaneous coronary and peripheral revascularization? Circulation 123(7):779–797, 2011.

    Article  Google Scholar 

  15. Palmerini T, Biondi-Zoccai G, Della Riva D, Mariani A, Genereux P, Branzi A, et al. Stent thrombosis with drug-eluting stents: is the paradigm shifting? Journal of the American College of Cardiology. 2013;62(21):1915-21.

  16. Perego, G., G. Cella, and C. Bastioli. Effect of molecular weight and crystallinity on poly(lactic acid) mechanical properties. Polymer 59:37–43, 1996.

    Google Scholar 

  17. Sarasua, J. R., A. L. Arraiza, P. Balerdi, and I. Maiza. Crystallinity and mechanical properties of optically pure polylactides and their blends. Polym. Eng. Sci. 45:745–753, 2005.

    Article  Google Scholar 

  18. Sheth, M., R. Kumar, V. Dave, R. Gross, and S. McCarthy. Biodegradable polymer blends of poly(lactic acid) and poly(ethylene glycol). J. Appl. Polym. Sci. 66:1495–1505, 1997.

    Article  Google Scholar 

  19. Su, S. H., R. Y. Chao, C. L. Landau, K. D. Nelson, R. B. Timmons, R. S. Meidell, et al. Expandable bioresorbable endovascular stent. I. Fabrication and properties. Ann. Biomed. Eng. 31(6):667–677, 2003.

    Article  Google Scholar 

  20. Tamai, H., K. Igaki, E. Kyo, K. Kosuga, A. Kawashima, S. Matsui, et al. Initial and 6-month results of biodegradable poly-l-lactic acid coronary stents in humans. Circulation 102(4):399–404, 2000.

    Article  Google Scholar 

  21. Tsuji, H., and Y. Ikada. Properties and morphologies of poly(L-lactide), Part 1: annealing condition effects on properties and morphologies of poly(L-lactide). Polymer 36:2709–2716, 1995.

    Article  Google Scholar 

  22. Tsuji, T., and Y. Ikada. Crystallization from the melt of pLA with different optical purities and their blends. Macromol. Chem. Phys. 197:3483–3499, 1996.

    Article  Google Scholar 

  23. Tsuji, H., and Y. Ikada. Stereocomplex formation between enantiomeric poly(lactic acid)s. XI. Mechanical properties and morphology of solution cast films. Polymer 40:6699–6708, 1999.

    Article  Google Scholar 

  24. Turner, J. F. I. I., A. Riga, A. O’Connor, J. Zhang, and J. Collis. Charcterization of drawn and undrawn poly-L-lactide films by differential scanning calorimetry. J. Therm. Anal. Calorim. 76:257–268, 2004.

    Article  Google Scholar 

  25. van der Giessen, W. J., A. M. Lincoff, R. S. Schwartz, H. M. van Beusekom, P. W. Serruys, D. R. Holmes, Jr., et al. Marked inflammatory sequelae to implantation of biodegradable and nonbiodegradable polymers in porcine coronary arteries. Circulation 94(7):1690–1697, 1996.

    Article  Google Scholar 

  26. Weir NA, Buchanan FJ, Orr JF, Dickson GR. Degradation of poly-L-lactide. Part 1: in vitro and in vivo physiological temperature degradation. Proceedings of the Institution of Mechanical Engineers Part H, Journal of engineering in medicine. 2004;218(5):307-19.

  27. Welch, T., R. C. Eberhart, and C. J. Chuong. Characterizing the expansive deformation of a bioresorbable polymer fiber stent. Ann. Biomed. Eng. 36(5):742–751, 2008.

    Article  Google Scholar 

  28. Welch, T. R., R. C. Eberhart, and C. J. Chuong. The influence of thermal treatment on the mechanical characteristics of a PLLA coiled stent. J. Biomed. Mater. Res. B 90(1):302–311, 2009.

    Google Scholar 

  29. Zilberman, M., R. C. Eberhart, and N. D. Schwade. In vitro study of drug-loaded bioresorbable films and support structures. J. Biomater. Sci. Polym. Ed. 13(11):1221–1240, 2002.

    Article  Google Scholar 

  30. Zilberman, M., K. D. Nelson, and R. C. Eberhart. Mechanical properties and in vitro degradation of bioresorbable fibers and expandable fiber-based stents. J. Biomed. Mater. Res. B. 74(2):792–799, 2005.

    Article  Google Scholar 

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Acknowledgments

We thank Ms. Martha Gracey and Dr. Howard Arnott of the Biology Department, UT Arlington, for their help in SEM image generation.

Conflict of Interest

Dr. Tré R. Welch, Dr. Robert C. Eberhart, Dr. Joan Reisch, and Dr. Cheng-Jen Chuong has no conflict of interest. No human and or animal studies were carried out by the authors for this article.

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Authors and Affiliations

  1. Department of Pediatric Cardiovascular Thoracic Surgery, University of Texas at Southwestern Medical Center of Dallas, Dallas, TX, 75390-9130, USA

    Tré R. Welch

  2. Department of Surgery, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, 75390-9130, USA

    Robert C. Eberhart

  3. Bioengineering Department, University of Texas at Arlington, Arlington, TX, 76019, USA

    Robert C. Eberhart & Cheng-Jen Chuong

  4. Department of Biostatistics, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, 75390-9130, USA

    Joan Reisch

Authors
  1. Tré R. Welch
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  2. Robert C. Eberhart
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  4. Cheng-Jen Chuong
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Correspondence to Tré R. Welch.

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Associate Editor Ajit P. Yoganathan oversaw the review of this article.

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Welch, T.R., Eberhart, R.C., Reisch, J. et al. Influence of Thermal Annealing on the Mechanical Properties of PLLA Coiled Stents. Cardiovasc Eng Tech 5, 270–280 (2014). https://doi.org/10.1007/s13239-014-0189-3

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  • DOI: https://doi.org/10.1007/s13239-014-0189-3

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