Planar biaxial testing of heart valve cusp replacement biomaterials: Experiments, theory and material constants

Labrosse, Michel R.; Jafar, R. Haj Mohammad; Ngu, Janet M.C.; Boodhwani, Munir

doi:10.1016/j.actbio.2016.08.036

Cited by 32 publications

(43 citation statements)

References 41 publications

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“…To our knowledge, the only two studies that have used multi-protocol planar biaxial testing to characterize and compare the mechanical properties of BP and PP tissues were conducted by Li and Sun [36] and Labrosse et at. [37]. Li and Sun found PP tissues to be more compliant than BP tissues, differing from the results presented in this study.…”

Section: Discussioncontrasting

confidence: 99%

“…Li and Sun found PP tissues to be more compliant than BP tissues, differing from the results presented in this study. More recently, Labrosse et al [37] conducted a study that characterized the biaxial mechanical response of fresh and fixed PP, commercial BP patches (chemically-treated), and fresh porcine aortic valve leaflets. In the Labrosse et al study the GL-treated PP tissue was also more extensible than reported herein.…”

Section: Discussionmentioning

confidence: 99%

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Evaluation of transcatheter heart valve biomaterials: Biomechanical characterization of bovine and porcine pericardium

Caballero

Sulejmani

Martin

et al. 2017

Journal of the Mechanical Behavior of Biomedical Materials

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Objective Bovine pericardium (BP) has been identified as a choice biomaterial for the development of surgical bioprosthetic heart valves (BHV) and transcatheter aortic valves (TAV). Porcine pericardium (PP) and younger BP have been suggested as candidates TAV leaflet biomaterials for smaller-profile devices due to their reduced thickness; however, their mechanical and structural properties remain to be fully characterized. This study characterized the material properties of chemically treated thick (PPK) and thin (PPN) PP, as well as fetal (FBP), calf (CBP) and adult (ABP) BP tissues in order to better understand their mechanical behavior. Methods Planar biaxial testing and uniaxial failure testing methods were employed to quantify tissue mechanical responses and failure properties. Fiber characteristics were examined using histological analysis. Results ABP and CBP tissues were significantly stiffer and stronger than the younger FBP tissues. Histological analysis revealed a significantly larger concentration of thin immature collagen fibers in the FBP tissues than in the ABP and CBP tissues. While PP tissues were thinnest, they were stiffer and less extensible than the BP tissues. Conclusions Due to comparable mechanical properties but significantly reduced thickness, CBP tissue may be a more suitable material for TAV manufacturing than ABP tissue. FBP tissue, despite its reduced thickness and higher flexibility, was weaker and should be studied in more detail. Although PP tissues are the thinnest, they were least extensible and failed at earlier strain than BP tissues. The differences between PP and BP tissues should be further investigated and suggest that they should not be used interchangeably in the manufacturing of TAV.

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Section: Discussioncontrasting

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Evaluation of transcatheter heart valve biomaterials: Biomechanical characterization of bovine and porcine pericardium

Caballero

Sulejmani

Martin

et al. 2017

Journal of the Mechanical Behavior of Biomedical Materials

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“…Similar convexity analysis is also required for constitutive models with a large number of parameters, e.g., Fung’s law (Labrosse et al. 2016). …”

Section: Discussionmentioning

confidence: 99%

“…2014; Labrosse et al. 2016), perform poorly in the presence of narrow valleys in the functional (Nocedal and Wright 2006). Therefore, the improvements from proposed modifications may be even greater for those methods.…”

Section: Discussionmentioning

confidence: 99%

An improved parameter estimation and comparison for soft tissue constitutive models containing an exponential function

Aggarwal

2017

Biomech Model Mechanobiol

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Motivated by the well-known result that stiffness of soft tissue is proportional to the stress, many of the constitutive laws for soft tissues contain an exponential function. In this work, we analyze properties of the exponential function and how it affects the estimation and comparison of elastic parameters for soft tissues. In particular, we find that as a consequence of the exponential function there are lines of high covariance in the elastic parameter space. As a result, one can have widely varying mechanical parameters defining the tissue stiffness but similar effective stress–strain responses. Drawing from elementary algebra, we propose simple changes in the norm and the parameter space, which significantly improve the convergence of parameter estimation and robustness in the presence of noise. More importantly, we demonstrate that these changes improve the conditioning of the problem and provide a more robust solution in the case of heterogeneous material by reducing the chances of getting trapped in a local minima. Based upon the new insight, we also propose a transformed parameter space which will allow for rational parameter comparison and avoid misleading conclusions regarding soft tissue mechanics.

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“…Soft tissues, such as heart valve leaflets, possess unique biophysical and biomechanical features that confer on them complex nonlinear, stress‐strain properties . The anisotropic nature of valve leaflets enables them to withstand a larger bending in the circumferential (or fiber) direction compared with its radial (or cross‐fiber) direction.…”

Section: Introductionmentioning

confidence: 99%

Valve leaflet‐inspired elastomeric scaffolds with tunable and anisotropic mechanical properties

Xue

Ravishankar

Zeballos

et al. 2019

Polymers for Advanced Techs

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Fibrous scaffolds, which can mimic the elastic and anisotropic mechanical properties of native tissues, hold great promise in recapitulating the native tissue microenvironment. We previously fabricated electrospun fibrous scaffolds made of hybrid synthetic elastomers (poly(1,3‐diamino‐2‐hydroxypropane‐co‐glycerol sebacate)‐co‐poly (ethylene glycol) (APS‐co‐PEG) and polycaprolactone (PCL)) to obtain uniaxial mechanical properties similar to those of human aortic valve leaflets. However, conventional electrospinning process often yields scaffolds with random alignment, which fails to recreate the anisotropic nature of most of the soft tissues such as native heart valves. Inspired by the structure of native valve leaflet, we designed a novel valve leaflet‐inspired ring‐shaped collector to modulate the electrospun fiber alignment and studied the effect of polymer formulation (PEG amount [mole %] in APS‐co‐PEG; ratio between APS‐co‐PEG and PCL; and total polymer concentration) in tuning the biaxial mechanical properties of the fibrous scaffolds. The fibrous scaffolds collected on the ring‐shaped collector displayed anisotropic biaxial mechanical properties, suggesting that their biaxial mechanical properties are closely associated with the fiber alignment in the scaffold. Additionally, the scaffold stiffness was easily tuned by changing the composition and concentration of the polymer blend. Human valvular interstitial cells (hVICs) cultured on these anisotropic scaffolds displayed aligned morphology as instructed by the fiber alignment. Overall, we generated a library of biologically relevant fibrous scaffolds with tunable mechanical properties, which will guide the cellular alignment.

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Planar biaxial testing of heart valve cusp replacement biomaterials: Experiments, theory and material constants

Cited by 32 publications

References 41 publications

Evaluation of transcatheter heart valve biomaterials: Biomechanical characterization of bovine and porcine pericardium

Evaluation of transcatheter heart valve biomaterials: Biomechanical characterization of bovine and porcine pericardium

An improved parameter estimation and comparison for soft tissue constitutive models containing an exponential function

Valve leaflet‐inspired elastomeric scaffolds with tunable and anisotropic mechanical properties

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