An improved texture correlation algorithm to measure substrate–cytoskeletal network strain transfer under large compressive strain

Zhao, Ruogang; Simmons, Craig A.

doi:10.1016/j.jbiomech.2011.10.003

Cited by 10 publications

(12 citation statements)

References 27 publications

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“…We note in particular that this method to measure the tissue force renders our technique insensitive to variations in the magnetic force that may arise from the $10% variability in the diameter of the Ni spheres or variation in the placement of the tweezer tip. The stress of the microtissues was calculated by dividing the tensile force by the cross-sectional area as detailed in the Methods section, and the strain distribution in the central region of the microtissue was determined by a texture correlation algorithm, 23 wherein the motion of features in the microtissue images was tracked over the grid shown superimposed on the phase contrast images in Fig. 3(b).…”

Section: Resultsmentioning

confidence: 99%

“…The strain over the central region of the microtissue was determined based on the sequential phase contrast images obtained during stretching, using a texture correlation image analysis algorithm. 23 Finally, the tensile elastic modulus of the central region was taken as the slope of the engineering stress-engineering strain curve (Fig. 3(c)).…”

Section: Microtissue Contraction Force and Stiffness Measurementmentioning

confidence: 99%

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Magnetic approaches to study collective three-dimensional cell mechanics in long-term cultures (invited)

Zhao

Boudou

Wang

et al. 2014

Journal of Applied Physics

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Contractile forces generated by cells and the stiffness of the surrounding extracellular matrix are two central mechanical factors that regulate cell function. To characterize the dynamic evolution of these two mechanical parameters during tissue morphogenesis, we developed a magnetically actuated micro-mechanical testing system in which fibroblast-populated collagen microtissues formed spontaneously in arrays of microwells that each contains a pair of elastomeric microcantilevers. We characterized the magnetic actuation performance of this system and evaluated its capacity to support long-term cell culture. We showed that cells in the microtissues remained viable during prolonged culture periods of up to 15 days, and that the mechanical properties of the microtissues reached and maintained at a stable state after a fast initial increase stage. Together, these findings demonstrate the utility of this microfabricated bio-magneto-mechanical system in extended mechanobiological studies in a physiologically relevant 3D environment. V C 2014 AIP Publishing LLC.

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Section: Resultsmentioning

confidence: 99%

Section: Microtissue Contraction Force and Stiffness Measurementmentioning

confidence: 99%

Magnetic approaches to study collective three-dimensional cell mechanics in long-term cultures (invited)

Zhao

Boudou

Wang

et al. 2014

Journal of Applied Physics

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“…The engineering stress of the microtissue was calculated as σ = F/A. The strain over the central region of the microtissue was determined based on sequential phase contrast images obtained during stretching, using a texture correlation image analysis algorithm [30]. The tensile elastic modulus of the central region was taken as the slope of the engineering stress-engineering strain curve.…”

Section: Methodsmentioning

confidence: 99%

Force-driven evolution of mesoscale structure in engineered 3D microtissues and the modulation of tissue stiffening

2014

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The complex structures of tissues determine their mechanical strength. In engineered tissues formed through self-assembly in a mold, artificially imposed boundary constraints have been found to induce anisotropic clustering of the cells and the extracellular matrix in local regions. To understand how such tissue remodeling at the intermediate length-scale (mesoscale) affects tissue stiffening, we used a novel microtissue mechanical testing system to manipulate the remodeling of the tissue structures and to measure the subsequent changes in tissue stiffness. Microtissues were formed through cell driven self-assembly of collagen matrix in arrays of micro-patterned wells, each containing two flexible micropillars that measured the microtissues’ contractile forces and also their elastic moduli via magnetic actuation. We manipulated tissue remodeling by inducing myofibroblast differentiation with TGF-β1, by varying the micropillar spring constants or by blocking cell contractility with blebbistatin and collagen cross-linking with BAPN. We showed that increased anisotropic compaction of the collagen matrix, caused by increased micropillar spring constant or elevated cell contraction force, contributed to tissue stiffening. Conversely, collagen matrix and tissue stiffness were not affected by inhibition of cell-generated contraction forces.. Together, these measurements showed that mesoscale tissue remodeling is an important middle step linking tissue compaction forces and tissue stiffening.

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“…The strain was measured locally in the microtissues’ centers from sequential phase contrast images, using a texture correlation analysis algorithm. 20 The elastic modulus was determined from the slope of the resulting stress-strain curves.…”

Section: Methodsmentioning

confidence: 99%

A microfabricated magnetic actuation device for mechanical conditioning of arrays of 3D microtissues

Zhao

Liu

et al. 2015

Lab Chip

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This paper describes an approach to actuate magnetically arrays of microtissue constructs for long-term mechanical conditioning and subsequent biomechanical measurements. Each construct consists of cell/matrix material self-assembled around a pair of flexible poly(dimethylsiloxane) (PDMS) pillars. The deflection of the pillars reports the tissues’ contractility. Magnetic stretching of individual microtissues via magnetic microspheres mounted on the cantilevers has been used to elucidate the tissues’ elastic modulus and response to varying mechanical boundary conditions. This paper describes the fabrication of arrays of micromagnetic structures that can transduce an externally applied uniform magnetic field to actuate simultaneously multiple microtissues. These structures are fabricated on silicon-nitride coated Si wafers and contain electrodeposited Ni bars. Through-etched holes provide optical and culture media access when the devices are mounted on the PDMS microtissue scaffold devices. Both static and AC forces (up to 20 μN on each microtissue) at physiological frequencies are readily generated in external fields of 40 mT. Operation of the magnetic arrays was demonstrated via measurements of elastic modulus and dynamic stiffening in response to AC actuation of fibroblast populated collagen microtissues.

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An improved texture correlation algorithm to measure substrate–cytoskeletal network strain transfer under large compressive strain

Cited by 10 publications

References 27 publications

Magnetic approaches to study collective three-dimensional cell mechanics in long-term cultures (invited)

Magnetic approaches to study collective three-dimensional cell mechanics in long-term cultures (invited)

Force-driven evolution of mesoscale structure in engineered 3D microtissues and the modulation of tissue stiffening

A microfabricated magnetic actuation device for mechanical conditioning of arrays of 3D microtissues

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