Mechanical stability of collagen fibril networks
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0898-L15-02.1
Mechanical stability of collagen fibril networks Gordon A. Shaw1, Dennis P. McDaniel2, John T. Elliott2, Alessandro Tona2, Anne L. Plant2 1
Manufacturing Engineering Laboratory National Institute of Standards and Technology Gaithersburg, MD 28099 USA
2
Chemical Science and Technology Laboratory National Institute of Standards and Technology Gaithersburg, MD 28099 USA
ABSTRACT Thin films of type 1 collagen fibril networks fabricated on alkanethiol-functionalized surfaces have been previously shown to provide an excellent protein matrix for cultured cells in applications such as drug toxicity studies and studies of cell signaling pathways. Cell phenotypic parameters, including cell morphology and rate of proliferation, can depend on the processing conditions used for fabrication of the protein films. The mechanical characteristics of the collagen fibril network appear to be particularly important, and as such, understanding the mechanical properties of individual fibrils, as well as their interactions with each other and the underlying substrate is critical for assuring a predictable response from cells. In this study, scanning probe microscopy and instrumented indentation are used in conjunction with small force metrology to examine the mechanical properties of these collagen fibrils and fibril networks. INTRODUCTION Recent advances in force metrology at NIST have allowed for traceable measurement of small forces with nanonewton resolution [1]. This has enabled new areas of inquiry in materials science, and in particular, biomechanics. Collagen is an extracellular matrix protein that is recognized for its exceptional elastic energy storage ability, and its strength and toughness [2]. Recent work at NIST has quantitatively demonstrated trends in the proliferation and spreading of smooth muscle cells (SMCs) on thin films of the extracellular matrix protein, type 1 collagen [3]. Differences are observed in the proliferation and spreading of SMCs based on thin film processing conditions. If the collagen is allowed to dry for several hours, spreading and proliferation of the SMCs are markedly enhanced. This effect is hypothesized to be linked to the mechanical properties of the collagen fibrils, since it is known that environmental mechanics can influence intracellular signaling events. In the current study, nanoindentation and quantitative atomic force microscope (AFM) force spectroscopy have been used in conjunction with rigorous small force metrology to examine the mechanical properties of individual collagen fibrils. The mechanical failure of individual collagen fibrils has been directly observed with nanoindentation, and qualitative differences can be seen in the AFM force spectroscopy data depending on collagen processing conditions.
0898-L15-02.2
EXPERIMENTAL Collagen fibril networks were prepared as described previously [3]. Briefly, a solution of type 1 collagen monomer was neutralized and adjusted for physiological ionic strength, and added to the surface of a Au and alkanethiol-coated glas
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