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Research Papers

Remote Determination of Time-Dependent Stiffness of Surface-Degrading-Polymer Scaffolds Via Synchrotron-Based Imaging

[+] Author and Article Information
N. K. Bawolin

Department of Mechanical Engineering,
College of Engineering,
University of Saskatchewan,
Saskatoon, SK S7N 5A9, Canada

X. B. Chen

Department of Mechanical Engineering,
College of Engineering,
University of Saskatchewan,
Saskatoon, SK S7N 5A9, Canada;
Department of Biomedical Engineering,
College of Engineering,
University of Saskatchewan,
Saskatoon, SK S7N 5A9, Canada

Manuscript received April 18, 2016; final manuscript received January 26, 2017; published online March 2, 2017. Assoc. Editor: Sean S. Kohles.

J Biomech Eng 139(4), 041004 (Mar 02, 2017) (8 pages) Paper No: BIO-16-1156; doi: 10.1115/1.4036021 History: Received April 18, 2016; Revised January 26, 2017

Surface-degrading polymers have been widely used to fabricate scaffolds with the mechanical properties appropriate for tissue regeneration/repair. During their surface degradation, the material properties of polymers remain approximately unchanged, but the scaffold geometry and thus mechanical properties vary with time. This paper presents a novel method to determine the time-dependent mechanical properties, particularly stiffness, of scaffolds from the geometric changes captured by synchrotron-based imaging, with the help of finite element analysis (FEA). Three-dimensional (3D) tissue scaffolds were fabricated from surface-degrading polymers, and during their degradation, the tissue scaffolds were imaged via the synchrotron-based imaging to characterize their changing geometry. On this basis, the stiffness behavior of scaffolds was estimated from the FEA, and the results obtained were compared to the direct measurements of scaffold stiffness from the load–displacement material testing. The comparison illustrates that the Young's moduli estimated from the FEA and characterized geometry are in agreement with the ones of direct measurements. The developed method of estimating the mechanical behavior was also demonstrated effective with a nondegrading scaffold that displays the nonlinear stress–strain behavior. The in vivo monitoring of Young's modulus by morphology characterization also suggests the feasibility of characterizing experimentally the difference between in vivo and in vitro surface degradation of tissue engineering constructs.

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Figures

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Fig. 1

(a) Scaffold design and coordinate system and (b) picture of the fabricated scaffold

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Fig. 2

(a) DEI image of scaffold and (b) PCI image of scaffold

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Fig. 3

Crystallinity of PCL scaffolds versus degradation time

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Fig. 4

Compressive stress–strain curves of FullCure 720 and PCL bulk materials at a deflection rate of 10 mm/min for three cubelike samples of each biomaterial

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Fig. 5

Compressive stress–strain curves of PCL and FullCure720 scaffolds at a deflection rate of 10 mm/min

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Fig. 6

Decline in average scaffold strand radius with time from surface degradation

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Fig. 7

Compared imaging/FEM and empirically measured mechanical characterization of scaffold during surface degradation

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Fig. 8

Compared imaging/FEM and empirically measured stress–strain behavior characterization of a scaffold

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