Fibrin Gels Exhibit Improved Biological, Structural, and Mechanical Properties Compared with Collagen Gels in Cell-Based Tendon Tissue-Engineered Constructs

The molecules of the extracellular matrix in connective tissues are densely packed. Biofabrication methods to attain such molecular packing density are limited and electrochemical processing (EP) of monomeric collagen solutions is one of few means to attain molecular packing. During EP, the pH gradient between electrodes drives the electrophoretic mobility of collagen molecules toward the isoelectric point where molecules are compacted. Our earlier work used linear electrodes to fabricate highly aligned crosslinked collagen fibers for tendon tissue engineering [1–4]. Prior work compared electrocompacted-aligned matrices with uncompacted randomly oriented ones. Therefore, the effects of alignment and compaction were compounded in terms of assessing cell response. So as to take the matrix alignment variable out of the picture to investigate matrix compaction effects only, we employed disc shaped electrodes to obtain electrocompacted sheets which lack matrix alignment. The current study investigated: a) the degree of compaction, b) effect of compaction on the mechanical properties of the sheets, and, c) mesenchymal stem cell (MSC) proliferation and morphology on compacted sheets relative to uncompacted collagen gels.

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Effect of Freezing on Cell Viability and Mechanical Strength of Bioartificial Tissues

10.1115/imece2001/htd-24431 ◽

2001 ◽

Author(s):

Ramachandra V. Devireddy ◽

Michael R. Neidert ◽

John C. Bischof ◽

Robert T. Tranquillo

Keyword(s):

Mechanical Properties ◽

Mechanical Strength ◽

Cell Viability ◽

Ultimate Tensile Stress ◽

Collagen Gels ◽

Cooling Rates ◽

Human Foreskin Fibroblasts ◽

Lower Strain ◽

Maximum Stiffness ◽

Eden Prairie

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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Stress-Dependent Effects of Platelet-Derived Growth Factor-BB on Fibroblast Migration and Traction Differ in Collagen and Fibrin

10.1115/imece2000-2575 ◽

2000 ◽

Author(s):

David I. Shreiber ◽

Paul A. J. Enever ◽

Robert T. Tranquillo

Keyword(s):

Type I Collagen ◽

Cell Behavior ◽

Environmental Cues ◽

Type I ◽

Collagen Gels ◽

Fibrin Gels ◽

Fibroblast Migration ◽

Tissue Equivalents ◽

Stress Dependent ◽

Statistical Conclusion

Abstract We used our novel assays of cell behavior in tissue equivalents to study the dose-response effects of PDGF-BB on RDF migration and traction in mechanically stressed and stress-free type I collagen and fibrin gels. PDGF-BB increased fibroblast migration significantly in all assays, but the effects on traction depended on the presence of stress and the nature of the ECM. PDGF-BB decreased fibroblast traction in stressed collagen gels, but increased traction in stress-free gels. No statistical conclusion could be inferred for stressed fibrin gels, and increasing PDGF-BB decreased traction in stress-free fibrin gels. These results demonstrate the complex response of fibroblasts to environmental cues, and point to opportunities to orchestrate cell behavior to affect the outcome of wound healing.

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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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The influence of fibrillin‐1 and physical activity upon tendon tissue morphology and mechanical properties in mice

Physiological Reports ◽

10.14814/phy2.14267 ◽

2019 ◽

Vol 7 (21) ◽

Cited By ~ 3

Author(s):

Peter H. T. Tran ◽

Tanja Skrba ◽

Elisabeth Wondimu ◽

Giuseppina Galatioto ◽

René Brüggebusch Svensson ◽

...

Keyword(s):

Physical Activity ◽

Mechanical Properties ◽

Tendon Tissue ◽

Tissue Morphology ◽

Fibrillin 1 ◽

Morphology And Mechanical Properties

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Elasticity of Fibrin and Protofibrin Gels ls Differentially Modulated by Calcium and Zinc

Thrombosis and Haemostasis ◽

10.1055/s-0038-1647523 ◽

1988 ◽

Vol 59 (03) ◽

pp. 500-503 ◽

Cited By ~ 12

Author(s):

Gerard Marx

Keyword(s):

Mechanical Properties ◽

Elastic Modulus ◽

Divalent Cations ◽

Maximum Level ◽

Large Excess ◽

Rate Of Development ◽

Fibrin Gels ◽

Opposing Effects

SummaryThe mechanical properties of fibrin and protofibrin gels in the presence of physiologic levels of Ca(II) and Zn(II) are described. As monitored with a thrombelastograph, Ca(II) (0.5–2 mM) increases the rate of development and the maximum level of gel elastic modulus (G) of fibrin and protofibrin gels. Zn(II) (10–50 μM) decreases the elastic modulus of those gels, even in the presence of a large excess of Ca(II). This contrasts with the ability of both divalent cations to increase fibrin and protofibrin gel turbidity. Unlike the turbidity or fibre thickness of fibrin and protofibrin gels, both of which are increased by these cations, gel elasticity is increased by Ca(II) but decreased by Zn(II). h is demonstrated that Ca(II) and Zn(II) modulate fibrin and protofibrin gels independently of one another, and that they have opposing effects on the mechanical properties of the gels. The disparity between the visual (turbidity, TEM) and the mechanical (elasticity) properties of (proto)fibrin gels indicates the need for new conceptual and analytic paradigms.

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Mechanical Properties of Collagen-Fibrin Co-Gels

ASME 2009 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2009-206700 ◽

2009 ◽

Author(s):

Victor K. Lai ◽

Edward A. Sander ◽

Robert T. Tranquillo ◽

Victor H. Barocas

Keyword(s):

Mechanical Properties ◽

Healing Process ◽

Mechanical Tests ◽

Functional Requirements ◽

Interpenetrating Networks ◽

Modeling Framework ◽

Fibrin Gels ◽

Multi Scale ◽

Engineered Tissues ◽

Anisotropic Mechanical Properties

Achieving desired mechanical properties is critical to meeting the functional requirements of engineered tissues. Mechanical function is inextricably linked to tissue structure. For example, replacement of fibrin with collagen during the healing process results in compositional heterogeneity which governs mechanical strength and function. Artificial tissues engineered using biopolymers such as fibrin and collagen can undergo a remodeling process that produces a compositionally and structurally complex tissue equivalent (TE) with anisotropic mechanical properties. TE functionality is assessed in part through mechanical testing, but the TE response is dependent on multi-scale interactions, which are dependent on a heterogeneously distributed microstructure, and are therefore difficult to interpret. In order to unravel the coupling between TE microstructure and macroscopic mechanical behavior, we have developed a multi-scale modeling framework for incorporating single component microstructural networks [1]. To expand our modeling framework, it is necessary to incorporate interpenetrating fibrin and collagen networks. This issue is particularly critical towards understanding the remodeling process that occurs in fibrin gels, which gradually replace fibrin with collagen networks. In this work, we have begun to investigate interpenetrating fibrin-collagen co-gels by varying the co-gel composition and subjecting the gels to uniaxial mechanical tests [2]. This study lays the experimental foundation for determining how to construct interpenetrating networks for our multiscale modeling framework, which will ultimately allows us to better assess and predict TE mechanics and produce better engineered tissues.

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Mechanical properties of collagen gels derived from rats of different ages

Journal of Biomaterials Science Polymer Edition ◽

10.1163/156856205774269494 ◽

2005 ◽

Vol 16 (10) ◽

pp. 1261-1275 ◽

Cited By ~ 43

Author(s):

Ching-Chou WU ◽

Shinn-Jyh Ding ◽

Yao-Hsien Wang ◽

Ming-Jer Tang ◽

Hsien-Chang Chang

Keyword(s):

Mechanical Properties ◽

Collagen Gels ◽

Different Ages

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Fibrin gels and their clinical and bioengineering applications

Journal of The Royal Society Interface ◽

10.1098/rsif.2008.0327 ◽

2008 ◽

Vol 6 (30) ◽

pp. 1-10 ◽

Cited By ~ 374

Author(s):

Paul A Janmey ◽

Jessamine P Winer ◽

John W Weisel

Keyword(s):

Mechanical Properties ◽

Wound Healing ◽

Cell Migration ◽

Network Architecture ◽

Blood Clotting ◽

Reaction Conditions ◽

Fibrin Gels ◽

Physiological Conditions ◽

Small Strains ◽

Fibrin Network

Fibrin gels, prepared from fibrinogen and thrombin, the key proteins involved in blood clotting, were among the first biomaterials used to prevent bleeding and promote wound healing. The unique polymerization mechanism of fibrin, which allows control of gelation times and network architecture by variation in reaction conditions, allows formation of a wide array of soft substrates under physiological conditions. Fibrin gels have been extensively studied rheologically in part because their nonlinear elasticity, characterized by soft compliance at small strains and impressive stiffening to resist larger deformations, appears essential for their function as haemostatic plugs and as matrices for cell migration and wound healing. The filaments forming a fibrin network are among the softest in nature, allowing them to deform to large extents and stiffen but not break. The biochemical and mechanical properties of fibrin have recently been exploited in numerous studies that suggest its potential for applications in medicine and bioengineering.

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