An annulus fibrosus closure device based on a biodegradable shape-memory polymer network

Shahriar Sharifi, Theo G. van Kooten, Hendrik-Jan C. Kranenburg, Bjorn P. Meij, Marc Behl, Andreas Lendlein, Dirk W. Grijpma*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

58 Citations (Scopus)

Abstract

Injuries to the intervertebral disc caused by degeneration or trauma often lead to tearing of the annulus fibrosus (AF) and extrusion of the nucleus pulposus (NP). This can compress nerves and cause lower back pain. In this study, the characteristics of poly(D,L-lactide-co-trimethylene carbonate) networks with shape-memory properties have been evaluated in order to prepare biodegradable AF closure devices that can be implanted minimally invasively. Four different macromers with (D,L-lactide) to trimethylene carbonate (DLLA:TMC) molar ratios of 80:20, 70:30, 60:40 and 40:60 with terminal methacrylate groups and molecular weights of approximately 30 kg mol(-1) were used to prepare the networks by photo-crosslinking. The mechanical properties of the samples and their shape-memory properties were determined at temperatures of 0 degrees C and 40 degrees C by tensile tests- and cyclic, thermo-mechanical measurements. At 40 degrees C all networks showed rubber-like behavior and were flexible with elastic modulus values of 1.7-2.5 MPa, which is in the range of the modulus values of human annulus fibrosus tissue. The shape-memory characteristics of the networks were excellent with values of the shape-fixity and the shape-recovery ratio higher than 98 and 957, respectively. The switching temperatures were between 10 and 39 degrees C. In vitro culture and qualitative immunocytochemistry of human annulus fibrosus cells on shape-memory films with DLLA:TMC molar ratios of 60:40 showed very good ability of the networks to support the adhesion and growth of human AF cells. When the polymer network films were coated by adsorption of fibronectin, cell attachment, cell spreading, and extracellular matrix production was further improved. Annulus fibrosus closure devices were prepared from these AF cell-compatible materials by photo-polymerizing the reactive precursors in a mold. Insertion of the multifunctional implant in the disc of a cadaveric canine spine showed that these shape-memory devices could be implanted through a small slit and to some extent deploy self-sufficiently within the disc cavity. (c) 2013 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)8105-8113
Number of pages9
JournalBiomaterials
Volume34
Issue number33
DOIs
Publication statusPublished - Nov-2013

Keywords

  • D,L-lactide and trimethylene carbonate-based networks
  • Photo-crosslinking
  • Shape-memory
  • Thermo-mechanical analysis
  • Intervertebral disk
  • Annulus fibrosus
  • INTERVERTEBRAL DISC
  • NUCLEUS REPLACEMENT
  • BIOMEDICAL APPLICATIONS
  • MODEL
  • FIBRONECTIN
  • PULPOSUS
  • MATRIX
  • CELL
  • LIMITATIONS
  • STABILITY

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