Dynamic mechanical properties of murine brain tissue using micro-indentation

MacManus, David B.; Pierrat, Baptiste; Murphy, Jeremiah G.; Gilchrist, Michael D.

doi:10.1016/j.jbiomech.2015.06.028

Cited by 36 publications

(38 citation statements)

References 31 publications

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“…Figures 11 and 12 illustrate that brain tissue not only stiffens with increasing strain but also with increasing strain rate. Rate-dependence of brain stiffness has consistently been reported in the literature using different testing techniques: shear testing or oscillatory shear testing [44,127,151], uniaxial compression or tension [57,83,85,132,137,140], indentation [20,107,136,163], and magnetic resonance elastography [36,145]. Figure 11 illustrates uniaxial compression, tension, and simple shear experiments performed at strain rates of 0.33 and 0.0067 1/s, respectively.…”

Section: Brain Stiffness Increases With Increasing Strain Ratementioning

confidence: 78%

Fifty Shades of Brain: A Review on the Mechanical Testing and Modeling of Brain Tissue

Budday

Ovaert

Holzapfel

et al. 2019

Arch Computat Methods Eng

308

288

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Brain tissue is not only one of the most important but also the most complex and compliant tissue in the human body. While long underestimated, increasing evidence confirms that mechanics plays a critical role in modulating brain function and dysfunction. Computational simulations-based on the field equations of nonlinear continuum mechanics-can provide important insights into the underlying mechanisms of brain injury and disease that go beyond the possibilities of traditional diagnostic tools. Realistic numerical predictions, however, require mechanical models that are capable of capturing the complex and unique characteristics of this ultrasoft, heterogeneous, and active tissue. In recent years, contradictory experimental results have caused confusion and hindered rapid progress. In this review, we carefully assess the challenges associated with brain tissue testing and modeling, and work out the most important characteristics of brain tissue behavior on different length and time scales. Depending on the application of interest, we propose appropriate mechanical modeling approaches that are as complex as necessary but as simple as possible. This comprehensive review will, on the one hand, stimulate the design of new experiments and, on the other hand, guide the selection of appropriate constitutive models for specific applications. Mechanical models that capture the complex behavior of nervous tissues and are accurately calibrated with reliable and comprehensive experimental data are key to performing reliable predictive simulations. Ultimately, mathematical modeling and computational simulations of the brain are useful for both biomedical and clinical communities, and cover a wide range of applications ranging from predicting disease progression and estimating injury risk to planning surgical procedures.

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Section: Brain Stiffness Increases With Increasing Strain Ratementioning

confidence: 78%

Fifty Shades of Brain: A Review on the Mechanical Testing and Modeling of Brain Tissue

Budday

Ovaert

Holzapfel

et al. 2019

Arch Computat Methods Eng

308

288

View full text Add to dashboard Cite

show abstract

“…Hydrogels of varying stiffnesses and geometries could also be combined together to match the heterogeneity demonstrated in normal brain tissue [55,56] that is likely causing the high variability in brain tumor results in this study. However, if intra-sample heterogeneity is critical to one’s hypothesis or experiment, our techniques would not be the best to determine appropriate surrogates.…”

Section: Resultsmentioning

confidence: 99%

Mechanical characterization of human brain tumors from patients and comparison to potential surgical phantoms

Stewart¹,

Rubiano²,

Dyson³

et al. 2017

PLoS ONE

107

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While mechanical properties of the brain have been investigated thoroughly, the mechanical properties of human brain tumors rarely have been directly quantified due to the complexities of acquiring human tissue. Quantifying the mechanical properties of brain tumors is a necessary prerequisite, though, to identify appropriate materials for surgical tool testing and to define target parameters for cell biology and tissue engineering applications. Since characterization methods vary widely for soft biological and synthetic materials, here, we have developed a characterization method compatible with abnormally shaped human brain tumors, mouse tumors, animal tissue and common hydrogels, which enables direct comparison among samples. Samples were tested using a custom-built millimeter-scale indenter, and resulting force-displacement data is analyzed to quantify the steady-state modulus of each sample. We have directly quantified the quasi-static mechanical properties of human brain tumors with effective moduli ranging from 0.17–16.06 kPa for various pathologies. Of the readily available and inexpensive animal tissues tested, chicken liver (steady-state modulus 0.44 ± 0.13 kPa) has similar mechanical properties to normal human brain tissue while chicken crassus gizzard muscle (steady-state modulus 3.00 ± 0.65 kPa) has similar mechanical properties to human brain tumors. Other materials frequently used to mimic brain tissue in mechanical tests, like ballistic gel and chicken breast, were found to be significantly stiffer than both normal and diseased brain tissue. We have directly compared quasi-static properties of brain tissue, brain tumors, and common mechanical surrogates, though additional tests would be required to determine more complex constitutive models.

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“…On the whole organ level, magnetic resonance elastography suggests that gray and white matter are rather indistinguishable in vivo, both in ferrets [4] and humans [19]. Discrepancies in these measurements not only reflect the extreme strain rate sensitivity of brain tissue, but also its non-linear behavior [15,20] and its compression stiffening [21]. This study seeks to unravel the ongoing controversy between gray and white matter stiffness measurements.…”

Section: Motivationmentioning

confidence: 98%

“…A robust, reliable, and reproducible method to characterize the mechanical behavior of the brain is indentation testing [12]. While tissue indentation is only rarely used to probe living brain in vivo [13], it is currently gaining popularity as a high-resolution, high-fidelity approach to probe individual different regions of gray and white matter tissue in vitro [14,15]. On the cellular level, atomic force microscopy indentation suggests that gray matter is about twice as stiff as white matter, both in mice [16] and rats [17].…”

Section: Motivationmentioning

confidence: 99%

Brain stiffness increases with myelin content

et al. 2016

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Increasing evidence suggests that the mechanical environment of the brain plays an important role in neuronal development and disease. Reported stiffness values vary significantly, but the origin of these variations remains unknown. Here we show that stiffness of our brain is correlated to the underlying tissue microstructure and directly proportional to the local myelin content. Myelin has been discovered in 1854 as an insulating layer around nerve cells to improve electric signal propagation. Our study now shows that it also plays an important mechanical role: Using a combined mechanical characterization and histological characterization, we found that the white matter stiffness increases linearly with increasing myelin content, from 0.5kPa at a myelin content of 63-2.5kPa at 92%.

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Dynamic mechanical properties of murine brain tissue using micro-indentation

Cited by 36 publications

References 31 publications

Fifty Shades of Brain: A Review on the Mechanical Testing and Modeling of Brain Tissue

Fifty Shades of Brain: A Review on the Mechanical Testing and Modeling of Brain Tissue

Mechanical characterization of human brain tumors from patients and comparison to potential surgical phantoms

Brain stiffness increases with myelin content

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