Tensile mechanical properties of three-dimensional type I collagen extracellular matrices with varied microstructure.

The importance and priority of specific micro-structural and mechanical design parameters must be established to effectively engineer scaffolds (biomaterials) that mimic the extracellular matrix (ECM) environment of cells and have clinical applications as tissue substitutes. In this study, three-dimensional (3-D) matrices were prepared from type I collagen, the predominant compositional and structural component of connective tissue ECMs, and structural-mechanical relationships were studied. Polymerization conditions, including collagen concentration (0.3-3 mg/mL) and pH (6-9), were varied to obtain matrices of collagen fibrils with different microstructures. Confocal reflection microscopy was used to assess specific micro-structural features (e.g., diameter and length) and organization of component fibrils in 3-D. Microstructural analyses revealed that changes in collagen concentration affected fibril density while maintaining a relatively constant fibril diameter. On the other hand, both fibril length and diameter were affected by the pH of the polymerization reaction. Mechanically, all matrices exhibited a similar stress-strain curve with identifiable "toe," "linear," and "failure" regions. However the linear modulus and failure stress increased with collagen concentration and were correlated with an increase in fibril density. Additionally, both the linear modulus and failure stress showed an increase with pH, which was related to an increasedfibril length and a decreasedfibril diameter. The tensile mechanical properties of the collagen matrices also showed strain rate dependence. Such fundamental information regarding the 3-D microstructural-mechanical properties of the ECM and its component molecules are important to our overall understanding of cell-ECM interactions (e.g., mechanotransduction) and the development of novel strategies for tissue repair and replacement.

[1]  M Abrahams,et al.  Mechanical behaviour of tendon in vitro. A preliminary report. , 1967, Medical & biological engineering.

[2]  M. Chiquet,et al.  Regulation of extracellular matrix gene expression by mechanical stress. , 1999, Matrix biology : journal of the International Society for Matrix Biology.

[3]  E. Baer,et al.  Collagen; ultrastructure and its relation to mechanical properties as a function of ageing , 1972, Proceedings of the Royal Society of London. Series B. Biological Sciences.

[4]  T. Allen,et al.  An ultrastructural review of collagen gels, a model system for cell-matrix, cell-basement membrane and cell-cell interactions. , 1984, Scanning electron microscopy.

[5]  J. Paul Robinson,et al.  Small Intestinal Submucosa: A Tissue-Derived Extracellular Matrix That Promotes Tissue-Specific Growth and Differentiation of Cells in Vitro , 1998 .

[6]  J. Paul Robinson,et al.  Three-dimensional imaging of extracellular matrix and extracellular matrix-cell interactions. , 2001, Methods in cell biology.

[7]  D. Swann,et al.  The formation and thermal stability of in vitro assembled fibrils from acid-soluble and pepsin-treated collagens. , 1979, Biochimica et biophysica acta.

[8]  F H Silver,et al.  Role of Storage on Changes in the Mechanical Properties of Tendon and Self-Assembled Collagen Fibers , 2000, Connective tissue research.

[9]  R. W. Little,et al.  A constitutive equation for collagen fibers. , 1972, Journal of biomechanics.

[10]  J.M.A. Lenihan,et al.  Biomechanics — Mechanical properties of living tissue , 1982 .

[11]  M. Dunn,et al.  Optimization of extruded collagen fibers for ACL reconstruction. , 1993, Journal of biomedical materials research.

[12]  F. Silver,et al.  An evaluation of purified reconstituted type 1 collagen fibers. , 1989, Journal of biomedical materials research.

[13]  F H Silver,et al.  Self-assembly of collagen fibers. Influence of fibrillar alignment and decorin on mechanical properties. , 1997, Biophysical journal.

[14]  E. J. Miller,et al.  Preparation and characterization of the different types of collagen. , 1982, Methods in enzymology.

[15]  C. S. Chen,et al.  Pore strain behaviour of collagen-glycosaminoglycan analogues of extracellular matrix. , 1995, Biomaterials.

[16]  A. Tözeren,et al.  Physical response of collagen gels to tensile strain. , 1995, Journal of biomechanical engineering.

[17]  W. Comper,et al.  Characterization of nuclei in in vitro collagen fibril formation , 1977, Biopolymers.

[18]  F H Silver,et al.  Assembly of type I collagen: fusion of fibril subunits and the influence of fibril diameter on mechanical properties. , 2000, Matrix biology : journal of the International Society for Matrix Biology.

[19]  S. Hsu,et al.  Viscoelastic studies of extracellular matrix interactions in a model native collagen gel system. , 1994, Biorheology.

[20]  A. Hiltner,et al.  Hierarchical structure of collagen composite systems: lessons from biology , 1991 .

[21]  S. Voytik-Harbin Three-dimensional extracellular matrix substrates for cell culture. , 2001, Methods in cell biology.

[22]  Donald E. Ingber,et al.  CHAPTER 9 – MECHANICAL AND CHEMICAL DETERMINANTS OF TISSUE DEVELOPMENT , 2000 .

[23]  P. Tracqui,et al.  Standardization of a method for characterizing low-concentration biogels: elastic properties of low-concentration agarose gels. , 1999, Journal of biomechanical engineering.

[24]  George D. Pins,et al.  Effects of static axial strain on the tensile properties and failure mechanisms of self-assembled collagen fibers , 1997 .

[25]  J. P. Robinson,et al.  Time-lapse confocal reflection microscopy of collagen fibrillogenesis and extracellular matrix assembly in vitro. , 2000, Biopolymers.

[26]  F H Silver,et al.  Mechanical properties of collagen fibres: a comparison of reconstituted and rat tail tendon fibres. , 1989, Biomaterials.

[27]  William D. Callister,et al.  Materials Science and Engineering: An Introduction , 1985 .

[28]  D A Parry,et al.  The molecular and fibrillar structure of collagen and its relationship to the mechanical properties of connective tissue. , 1988, Biophysical chemistry.

[29]  I. Yannas,et al.  Design of an artificial skin. I. Basic design principles. , 1980, Journal of biomedical materials research.

[30]  J. Lévêque,et al.  Measurement of mechanical forces generated by skin fibroblasts embedded in a three-dimensional collagen gel. , 1991, The Journal of investigative dermatology.

[31]  M S Kolodney,et al.  Isometric contraction by fibroblasts and endothelial cells in tissue culture: a quantitative study , 1992, The Journal of cell biology.

[32]  L. Petzold,et al.  Rheology of reconstituted type I collagen gel in confined compression , 1997 .

[33]  A. George,et al.  Fundamentals of Interstitial Collagen Self-Assembly , 1994 .

[34]  Mhj Koch,et al.  Quantitative analysis of the molecular sliding mechanisms in native tendon collagen — time-resolved dynamic studies using synchrotron radiation , 1987 .

[35]  G. C. Wood,et al.  The formation of fibrils from collagen solutions. 1. The effect of experimental conditions: kinetic and electron-microscope studies. , 1960, The Biochemical journal.

[36]  N. Isshiki,et al.  Influence of glycosaminoglycans on the collagen sponge component of a bilayer artificial skin. , 1990, Biomaterials.

[37]  Y. Ikada,et al.  Re-freeze dried bilayer artificial skin. , 1993, Biomaterials.