Mechanical properties of collagen gels derived from rats of different ages

Abstract The effect of freezing on the viability and mechanical strength of bioartificial tissues was determined under a variety of cooling conditions, with the ultimate aim of optimizing the cryopreservation process. Bioartificial tissues (i.e. tissue-equivalents or TEs) were prepared by incubating entrapped human foreskin fibroblasts in collagen gels for a period of 2 weeks. The bioartificial tissues were frozen using a controlled rate freezer at various cooling rates (0.5, 2, 5, 20, 40 and > 1000°C/min or slam freezing). The viability (< 60 min after thawing) of the fibroblasts in the bioartificial tissue was assessed using the Ethidium Homodimer (dead cells stain red) and Hoechst Give cells stain blue) assay. Uniaxial tension experiments were performed on an MTS Microbionix System (Eden Prairie, MN) to assess the post-thaw mechanical properties (Maximum Stiffness; Ultimate Tensile Stress; and Strain to Failure) of the frozen-thawed bioartificial tissue (≤ 3 hours after thawing). The results suggest that cooling rates of either 2 or 5°C/min are optimal for preserving both the cell viability and mechanical properties of the bioartificial tissues, post-freeze. Bioartificial tissues were also frozen using a directional solidification stage at 5°C/min. The post-thaw viability results are comparable in both the directionally cooled and the controlled rate freezer samples. However, the mechanical properties of the directionally cooled samples are significantly different (with a higher maximum stiffness and a lower strain to failure) than those obtained for samples frozen using a controlled rate freezer. This suggests that the directionality of ice propagation into the sample affects the measured mechanical properties.

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Development of Anisotropy in Fibroblast Populated Collagen Gels

Advances in Bioengineering ◽

10.1115/imece2002-32781 ◽

2002 ◽

Author(s):

Stavros Thomopoulos ◽

Vedran Knezevic ◽

Kevin D. Costa ◽

Jeffrey W. Holmes

Keyword(s):

Mechanical Properties ◽

Soft Tissues ◽

Mechanical Load ◽

The Other ◽

Collagen Structure ◽

Collagen Gels ◽

Specific Loading ◽

Anisotropic Mechanical Properties ◽

Muscle Loading ◽

Heart Wall

The development of anisotropic mechanical properties is critical for the successful tissue engineering of many soft tissues. Load bearing tissues naturally develop varying degrees of anisotropy, presumably in response to their specific loading environment. For example, the heart wall develops a collagen structure that varies in a predictable manner through its depth [1]. Tendon, on the other hand, develops a matrix that does not vary much in orientation and is highly aligned in the direction of muscle loading [2]. These varied levels of anisotropy may be due to inherent differences between the cells in each tissue, to differences in the mechanical load and boundary conditions seen by the cells, or to a combination of these factors.

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Collagen Network Topology is Influenced by Collagen Concentration, But Not by Co-Gelation With Fibrin

ASME 2011 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2011-53239 ◽

2011 ◽

Author(s):

Victor K. Lai ◽

Edward A. Sander ◽

Spencer P. Lake ◽

Robert T. Tranquillo ◽

Victor H. Barocas

Keyword(s):

Mechanical Properties ◽

Healing Process ◽

Biological Tissues ◽

Wound Healing Process ◽

Type I ◽

Collagen Gels ◽

Collagen Network ◽

Modeling Framework ◽

Collagen Concentration ◽

Cardiovascular Tissue

Extracellular matrix (ECM) proteins (e.g. collagen, elastin) play an important role in biological tissues. In addition to conferring mechanical strength to a tissue, the ECM provides a biochemical environment essential for modulation of cellular responses such as growth and migration. Collagens are the dominant protein of the ECM, with collagen type I being most abundant. Our group and others have shown that the mechanical properties of a collagen I matrix change with collagen concentration, and when formed in the presence of a secondary fibril network such as fibrin [1]. We are interested in collagen-fibrin systems because our group uses fibrin as the starting scaffold material for cardiovascular tissue engineering, which produces interpenetrating collagen-fibrin matrices during the remodeling process as the fibrin network is degraded and replaced with cell-deposited collagen [2]. Fibrin and collagen networks are also present together around the thrombus during the wound healing process. Research has shown that ECM mechanical properties are correlated with their overall network structure characteristics such as fibril diameter [3]. Currently we have a modeling framework that generates an ECM microstructural network which can be used to predict the overall properties of a bioengineered tissue [4]. This framework allows exploration of the structure-function relation, but how the structure depends on composition remains poorly understood, especially in multi-component gels. Thus, the objective of this work was to quantify the collagen network architecture in pure collagen gels of different concentrations and in collagen-fibrin co-gels.

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Fine grained concrete structures reliability assessment: theory and investigational studies

MATEC Web of Conferences ◽

10.1051/matecconf/201825102002 ◽

2018 ◽

Vol 251 ◽

pp. 02002 ◽

Cited By ~ 1

Author(s):

Sergey Parfenov ◽

Anatoly Alekseytsev ◽

Yuriy Vinokurov

Keyword(s):

Mechanical Properties ◽

Modulus Of Elasticity ◽

Experimental Studies ◽

Reliability Assessment ◽

Concrete Structures ◽

Fine Grained ◽

Different Ages ◽

Emergency Actions ◽

General Safety

Describes the theoretical preconditions of using mechanical properties of fine-grained concrete in the design of concrete structures subject to risks and the general safety. A technique for experimental studies and data on the fine-grained concrete deformative properties at different ages and different loading levels are presented. The regularities of the modulus of elasticity change from strength, type and age of concrete are revealed. Full diagrams of deformation of concrete are constructed. The results obtained can be used in the design of the fine-grained concrete structures in buildings having risks occurrence socioeconomic losses and able to resist of emergency actions.

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The Effect of Mechanical Constraints on Gelatin Samples under Pulsatile Flux

Materials Science Forum ◽

10.4028/www.scientific.net/msf.706-709.449 ◽

2012 ◽

Vol 706-709 ◽

pp. 449-454

Author(s):

Eugenia Blangino ◽

Martín A. Cagnoli ◽

Ramiro M. Irastorza ◽

Fernando Vericat

Keyword(s):

Mechanical Properties ◽

Tissue Engineering ◽

Collagen Gel ◽

Biological Tissues ◽

Mechanical Stimuli ◽

Collagen Gels ◽

Collagen Network ◽

Mechanical Constraints ◽

Preparation Conditions ◽

Biological Compatibility

It is of great interest in tissue engineering the role of collagen gel-based structures (scaffolds, grafts and-by cell seeded and maturation-tissue equivalents (TEs) for several purposes). It is expected the appropriate biological compatibility when the extracellular matrix (ECM) is collagen-based. Regarding the mechanical properties (MP), great efforts in tissue engineering are focused in tailoring TE properties by controlling ECM composition and organization. When cells are seeded, the collagen network is remodeled by cell-driven compaction and consolidation, produced mainly through the mechanical stimuli that can be directed selecting the geometry and the surfaces exposed to the cells. Collagen gels have different (chemical and mechanical) properties depending on their origin and preparation conditions. The MP of the collagen network are derived from the degree of cross-linking (CLD) which can be modified by different treatments. One of the techniques to evaluate MP in the network is by ultrasound (US). In this work we analyse the effect of several mechanical constraints (similar to that imposed to promote cell growth on certain sample surfaces, when seeded) on samples of gelatin with a specific geometry (thick walls cylinders) under loading conditions of pulsatile flow. We checked US parameters and estimates evolution of the network structure for different restrictions in the sample mobility. It was implemented by adapting devices specially built to measure elastic properties of biological tissues by US. The material (origin and purity) and the preparation conditions for the gelatin were selected in order to compare the results with those of literature.

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Predicting bulk mechanical properties of cellularized collagen gels using multiphoton microscopy

Acta Biomaterialia ◽

10.1016/j.actbio.2010.07.004 ◽

2010 ◽

Vol 6 (12) ◽

pp. 4657-4665 ◽

Cited By ~ 77

Author(s):

C.B. Raub ◽

A.J. Putnam ◽

B.J. Tromberg ◽

S.C. George

Keyword(s):

Mechanical Properties ◽

Multiphoton Microscopy ◽

Collagen Gels

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Study on the Mechanical Properties of Backfill Cream-Body during Coal Mining

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.170-173.533 ◽

2012 ◽

Vol 170-173 ◽

pp. 533-536 ◽

Cited By ~ 1

Author(s):

Shao Jie Chen ◽

Wei Jia Guo ◽

Hai Long Wang ◽

Yi Tao Zhong

Keyword(s):

Mechanical Properties ◽

Coal Mine ◽

Surface Mining ◽

Test System ◽

Control Surface ◽

Ecological Environment ◽

Uniaxial Compression Test ◽

Mechanical Parameters ◽

Test Results ◽

Different Ages

In order to research the mechanical properties of the backfill cream-body under engineering conditions in the coal mine, the uniaxial compression test of backfill cream-body with different ages abtained from the filling locale of Daizhuang coal mine is conducted with MTS815.03 rock test system. The characteristics of backfill cream-body in the limited space and a certain environment are studied. Research shows that, the strength of backfill cream-body is high, but coagulability is bad and the discreteness of mechanical properties is different; Uniaxial compressive strength is 2.3 ~ 13.17 MPa and the average is 5.436 MPa; The elastic modulus is very low ,which is only 53.66 ~ 2614.35 MPa and the average is 645.14 MPa. The deformation is bigger when absorbing load; Poisson's ratio is low, which is only 0.0001 ~ 0.2112 and the average is 0.0265, which indicates that the backfill cream-body doesn't need the space of transverse deformation when bearing compression deformation; The mechanical parameters of backfill cream-body with different ages are fitted and regressed. Test results is important to control surface mining subsidence effectively, liberate the coal resources under buildings, railways and waterbodies and protect the ecological environment.

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Neurite growth in 3D collagen gels with gradients of mechanical properties

Biotechnology and Bioengineering ◽

10.1002/bit.22074 ◽

2009 ◽

Vol 102 (2) ◽

pp. 632-643 ◽

Cited By ~ 117

Author(s):

Harini G. Sundararaghavan ◽

Gary A. Monteiro ◽

Bonnie L. Firestein ◽

David I. Shreiber

Keyword(s):

Mechanical Properties ◽

Neurite Growth ◽

Collagen Gels ◽

3D Collagen

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Design and construction of a novel measurement device for mechanical characterization of hydrogels: A case study

PLoS ONE ◽

10.1371/journal.pone.0247727 ◽

2021 ◽

Vol 16 (2) ◽

pp. e0247727

Author(s):

Shayan Shahab ◽

Mehran Kasra ◽

Alireza Dolatshahi-Pirouz

Keyword(s):

Mechanical Properties ◽

Shear Modulus ◽

Magnetic Beads ◽

Mechanical Characterization ◽

Collagen Gel ◽

Biological Tissues ◽

Elastic Behavior ◽

Collagen Gels ◽

Collagen Concentration

Natural biopolymer-based hydrogels especially agarose and collagen gels, considering their biocompatibility with cells and their capacity to mimic biological tissues, have widely been used for in-vitro experiments and tissue engineering applications in recent years; nevertheless their mechanical properties are not always optimal for these purposes. Regarding the importance of the mechanical properties of hydrogels, many mechanical characterization studies have been carried out for such biopolymers. In this work, we have focused on understanding the mechanical role of agarose and collagen concentration on the hydrogel strength and elastic behavior. In this direction, Amirkabir Magnetic Bead Rheometry (AMBR) characterization device equipped with an optimized electromagnet, was designed and constructed for the measurement of hydrogel mechanical properties. The operation of AMBR set-up is based on applying a magnetic field to actuate magnetic beads in contact with the gel surface in order to actuate the gel itself. In simple terms the magnetic beads leads give rise to mechanical shear stress on the gel surface when under magnetic influence and together with the associated bead-gel displacement it is possible to calculate the hydrogel shear modulus. Agarose and Collagen gels with respectively 0.2–0.6 wt % and 0.2–0.5 wt % percent concentrations were prepared for mechanical characterization in terms of their shear modulus. The shear modulus values for the different percent concentrations of the agarose gel were obtained in the range 250–650 Pa, indicating the shear modulus increases by increasing in the agar gel concentration. In addition to this, the values of shear modulus for the collagen gel increase as function of concentration in the range 240–520 Pa in accordance with an approximately linear relationship between collagen concentration and gel strength.

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pH Modification of High-Concentrated Collagen Bioinks as a Factor Affecting Cell Viability, Mechanical Properties, and Printability

Gels ◽

10.3390/gels7040252 ◽

2021 ◽

Vol 7 (4) ◽

pp. 252

Author(s):

Jana Stepanovska ◽

Martin Otahal ◽

Karel Hanzalek ◽

Monika Supova ◽

Roman Matejka

Keyword(s):

Mechanical Properties ◽

Cell Proliferation ◽

Cell Viability ◽

Limiting Factor ◽

Mechanical Resistance ◽

3D Bioprinting ◽

Collagen Gels ◽

High Concentration ◽

Collagen Concentration ◽

Static Conditions

The 3D bioprinting of cell-incorporated gels is a promising direction in tissue engineering applications. Collagen-based hydrogels, due to their similarity to extracellular matrix tissue, can be a good candidate for bioink and 3D bioprinting applications. However, low hydrogel concentrations of hydrogel (<10 mg/mL) provide insufficient structural support and, in highly concentrated gels, cell proliferation is reduced. In this study, we showed that it is possible to print highly concentrated collagen hydrogels with incorporated cells, where the viability of the cells in the gel remains very good. This can be achieved simply by optimizing the properties of the bioink, particularly the gel composition and pH modification, as well as by optimizing the printing parameters. The bioink composed of porcine collagen hydrogel with a collagen concentration of 20 mg/mL was tested, while the final bioink collagen concentration was 10 mg/mL. This bioink was modified with 0, 5, 9, 13, 17 and 20 μL/mL of 1M NaOH solution, which affected the resulting pH and gelling time. Cylindrical samples based on the given bioink, with the incorporation of porcine adipose-derived stromal cells, were printed with a custom 3D bioprinter. These constructs were cultivated in static conditions for 6 h, and 3 and 5 days. Cell viability and morphology were evaluated. Mechanical properties were evaluated by means of a compression test. Our results showed that optimal composition and the addition of 13 μL NaOH per mL of bioink adjusted the pH of the bioink enough to allow cells to grow and divide. This modification also contributed to a higher elastic modulus, making it possible to print structures up to several millimeters with sufficient mechanical resistance. We optimized the bioprinter parameters for printing low-viscosity bioinks. With this experiment, we showed that a high concentration of collagen gels may not be a limiting factor for cell proliferation.

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