Optical Measurement of Three-Dimensional Collagen Gel Constructs by Elastic Scattering Spectroscopy

Marenzana, Massimo; Pickard, David Christopher O.; MacRobert, AJ; Brown, Robert A.

doi:10.1089/107632702760184673

Cited by 15 publications

(9 citation statements)

References 26 publications

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“…The optical setup used was that described in detail and schematically by Marenzana et al 13 In brief, it consisted of a xenon white light source, a fiber optic probe, and a spectrometer (Ocean Optics, Dunedin, FL) and controlled by a notebook personal computer (PC). The custom-made optical probe contained a 400-mm source fiber and a 200-mm detector fiber, with a source-detector separation of~350 mm.…”

Section: Optical Setupmentioning

confidence: 99%

“…Further detail of the optical setup has been described previously. 12,13,15 Twenty-nine unloaded tendons from 8 animals were investigated for backscatter anisotropy with probe positions at 08 and 1808 (parallel) and 908 and 2708 (perpendicular) to the long axis of the unloaded tendon. 12 Figure 1 shows the mean spectra from the second forepaw digit (F2) for perpendicular and parallel probe positions; there was no statistically significant difference ( p < 0.05) between different animals.…”

Section: Optical Setupmentioning

confidence: 99%

“…Elastic scattering spectroscopy (ESS) has been developed to test its possible value in medical diagnostics and as a research tool. [10][11][12][13] Light delivered to a tissue surface can be reflected, refracted, absorbed, or scattered. That proportion of light that reemerges is termed backscattered light and can be picked up and analyzed by a collecting fiber adjacent to the illuminating fiber.…”

Section: Introductionmentioning

confidence: 99%

“…The extracellular matrix elements, in particular, give altered signals as structural reorganization occurs under applied tissue loading. [12][13][14][15] The volume of tissue studied is related to the separation distance between the light source and detector fiber: the larger the separation, the larger the volume studied. 18 Previous investigators have demonstrated optical anisotropy (i.e., tissue structural alignment affects spatial distribution of backscattered light) in aligned and partially aligned tissues, such as muscle 19 and skin.…”

Section: Introductionmentioning

confidence: 99%

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In SituMonitoring of Tendon Structural Changes by Elastic Scattering Spectroscopy: Correlation with Changes in Collagen Fibril Diameter and Crimp

et al. 2006

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The aim of this study was to monitor structural changes in loaded rabbit digital flexor tendons in situ and ex situ via elastic scattering spectroscopy (ESS). The optical setup consisted of a xenon white light source (lambda = 320-860 nm), connected to a fiber optic probe (with a source-detector separation of approximately 350 microm) and a spectrometer, controlled by a personal computer (PC). Cadaveric rabbit tendons were studied in situ under 3 tensional regimens: unloaded (no extrinsic tension applied), stretched, and 1-kg loaded and compared with excised tendons (i.e., no tension). Four times more light was detected in in situ unloaded tendons perpendicular to the tendon long axis than parallel to it. Backscatter anisotropy was expressed as the anisotropy factor (AF600nm: ratio of greatest to least backscatter intensity, measured with orthogonal probe positions). Differences in backscatter anisotropy between tendons from different digits were not significant. AF600nm had the smallest value (2.72 +/- 0.38) for the least aligned tendon preparations (excised tendons), and increased to 7.17 +/- 0.54 (1-kg loaded) as in situ loads were applied. Electron microscopy revealed that the distribution of collagen fibril diameters changed as loads were applied, with the diameter of larger fibrils decreasing approximately 33% for 1-kg loaded compared with excised tendons. Polarized light microscopy showed a characteristic crimp pattern in excised tendons, but this was hardly detectable in unloaded tendons and not detectable in tendons fixed in situ under a 1-kg load. We propose that the increase in optical anisotropy is a function of collagen fibril straightening and reducing fibril diameter as the tendon undergoes progressive loading. These findings are important for monitoring structure in vivo and in bioreactors for tissue engineers.

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Section: Optical Setupmentioning

confidence: 99%

Section: Optical Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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In SituMonitoring of Tendon Structural Changes by Elastic Scattering Spectroscopy: Correlation with Changes in Collagen Fibril Diameter and Crimp

et al. 2006

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“…Images were then analysed by using NIH Image software as previously described (Marenzana et al 2002). The total surface area was then used to normalize peak force values and to obtain adhesive strength values.…”

Section: Assessment Of Mechanical Integration Of Interfacesmentioning

confidence: 99%

A collagen-based interface construct for the assessment of cell-dependent mechanical integration of tissue surfaces

et al. 2006

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The interface between any newly engineered tissue and pre-existing tissue is of great importance to tissue engineering; however, this process has so far been largely ignored, with few reports regarding the mechanical strength of newly integrated connective tissues surfaces. A new model system has been developed to generate a well-defined interface between two collagen lattices: one pre-contracted by resident fibroblasts and the other a cell-free wrapping gel. This construct can be cultured for prolonged periods (>2 weeks) and can also be fitted onto a mechanical testing system to measure the interface adhesive strength at the end of the culture time. Interface adhesive strength shows a six-fold increase after 1 week in culture, compared with the time-zero baseline. Observations of cell migration across the interface suggest that cell translocation in the three-dimensional matrix might play an important role in the integration process. In this new controlled geometry, normal and shear stresses at the interface can be analysed by finite element modelling and the areas at which debonding starts can be defined. The current experimental design permits solid multiple (homogeneous or heterogeneous) interface formation in vitro with a well-defined geometry and the possibility of measuring mechanical linkage. This design should enable many other factors affecting cell-driven interface strengthening to be investigated.

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Micro-structured Materials and Mechanical Cues in 3D Collagen Gels

Phillips

Brown

2010

Methods in Molecular Biology

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Collagen gels provide a versatile and widely used substrate for three-dimensional (3D) cell culture. Here we describe how cell-seeded Type-I collagen gels can be adapted to provide powerful 3D models to support a wide range of research applications where cell/substrate alignment, density, stiffness/compliance, and strain are critical factors. In their fully hydrated form, rectangular collagen gels can be tethered such that endogenous forces generated as resident cells attach to and remodel the fibrillar collagen network can align the substrate in a controllable, predictable, and quantifiable manner. By removing water from collagen gels (plastic compression), their density increases towards that of body tissues, facilitating the engineering of a range of biomimetic constructs with controllable mechanical properties. This dense collagen can be used in combination with other components to achieve a range of functional properties from controlled perfusion, or tensile/compressive strength to new micro-structures. Detailed methodology is provided for the assembly of a range of 3D collagen materials including tethered aligned hydrogels and plastic compressed constructs. A range of techniques for analysing cell behaviour within these models, including microscopy and molecular analyses are described. These systems therefore provide a highly controllable mechanical and chemical micro-environment for investigating a wide range of cellular responses.

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Optical Measurement of Three-Dimensional Collagen Gel Constructs by Elastic Scattering Spectroscopy

Cited by 15 publications

References 26 publications

In SituMonitoring of Tendon Structural Changes by Elastic Scattering Spectroscopy: Correlation with Changes in Collagen Fibril Diameter and Crimp

In SituMonitoring of Tendon Structural Changes by Elastic Scattering Spectroscopy: Correlation with Changes in Collagen Fibril Diameter and Crimp

A collagen-based interface construct for the assessment of cell-dependent mechanical integration of tissue surfaces

Micro-structured Materials and Mechanical Cues in 3D Collagen Gels

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