The impact of long term freezing on the mechanical properties of porcine aortic tissue

Siobhan A. O'Leary, Barry J. Doyle, Tim M. McGloughlin

Research output: Contribution to journalArticlepeer-review

Abstract

Background: Preservation of the native artery[U+05F3]s functionality can be important in both clinical and experimental applications. Although, simple cryopreservation techniques offer an attractive solution to this problem, the extent to which freezing affects the tissue[U+05F3]s properties is widely debated. Earlier assessments of the mechanical properties post-freezing have been limited by one or more of the following: small sample numbers, uncontrolled inter-specimen/animal variability, failure to account for the impact of potential errors in thickness measurements, short storage times and uniaxial test methods. Material and methods: Biaxial mechanical tests were performed on porcine aortic samples (n=89) extracted from superior, middle and inferior regions of five aortas, stored in isotonic saline at -20°C for 1 day, 1 week, 1, 6 and 12 months, thawed and retested. The sample[U+05F3]s weight and thickness were also measured pre and post-freezing. A total of 178 tests were performed and elastic modulus was assessed by calculating the slope of the Cauchy stress-stretch curve at the low and high stretch regions in both the circumferential (θ) and longitudinal (L) directions. Results: The weight of the samples increased post-freezing. However, in general, no significant difference was found between the elastic modulus of porcine aortic tissue before and after freezing at -20°C and was unaffected by storage time. Although more accurate measuring instruments are warranted to confirm this finding, minor changes to the elastic modulus as a result of freezing were negatively correlated with regional variances i.e. changes in the elastic modulus decreased from the superior to the inferior region. Conclusions: These results indicate that for applications which require preservation of the gross mechanical properties, storing the tissue at -20. °C in isotonic saline, for an extended period of time, is acceptable.

Original languageEnglish
Pages (from-to)165-173
Number of pages9
JournalJournal of the Mechanical Behavior of Biomedical Materials
Volume37
DOIs
Publication statusPublished - Sep 2014

Keywords

  • Aortic tissue
  • Biaxial testing
  • Cryopreservation
  • Freezing
  • Long term storage
  • Mechanical properties
  • Preservation
  • Vascular

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