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Nanoindentation of histological specimens: Mapping the elastic properties of soft tissues

Published online by Cambridge University Press:  31 January 2011

R. Akhtar*
Affiliation:
School of Materials, University of Manchester, Manchester, M1 7HS, United Kingdom
N. Schwarzer
Affiliation:
Saxonian Institute of Surface Mechanics (SIO), Ummanz, 18569, Germany
M.J. Sherratt
Affiliation:
Tissue Injury and Repair Group, Faculty of Medical and Human Sciences, University of Manchester, Manchester, M13 9PT, United Kingdom
R.E.B. Watson
Affiliation:
Dermatological Sciences Research Group, Faculty of Medical and Human Sciences, University of Manchester, Manchester, M13 9PT, United Kingdom
H.K. Graham
Affiliation:
School of Materials, University of Manchester, Manchester, M1 7HS, United Kingdom
A.W. Trafford
Affiliation:
Unit of Cardiac Physiology, Division of Cardiovascular and Endocrine Sciences, University of Manchester, Manchester, United Kingdom
P.M. Mummery
Affiliation:
School of Materials, University of Manchester, Manchester, M1 7HS, United Kingdom
B. Derby
Affiliation:
School of Materials, University of Manchester, Manchester, M1 7HS, United Kingdom
*
a) Address all correspondence to this author. e-mail: [email protected]
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Abstract

Although alterations in the gross mechanical properties of dynamic and compliant tissues have a major impact on human health and morbidity, there are no well-established techniques to characterize the micromechanical properties of tissues such as blood vessels and lungs. We have used nanoindentation to spatially map the micromechanical properties of 5-μm-thick sections of ferret aorta and vena cava and to relate these mechanical properties to the histological distribution of fluorescent elastic fibers. To decouple the effect of the glass substrate on our analysis of the nanoindentation data, we have used the extended Oliver and Pharr method. The elastic modulus of the aorta decreased progressively from 35 MPa in the adventitial (outermost) layer to 8 MPa at the intimal (innermost) layer. In contrast, the vena cava was relatively stiff, with an elastic modulus >30 MPa in both the extracellular matrix-rich adventitial and intimal regions of the vessel. The central, highly cellularized, medial layer of the vena cava, however, had an invariant elastic modulus of ∼20 MPa. In extracellular matrix-rich regions of the tissue, the elastic modulus, as determined by nanoindentation, was inversely correlated with elastic fiber density. Thus, we show it is possible to distinguish and spatially resolve differences in the micromechanical properties of large arteries and veins, which are related to the tissue microstructure.

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Articles
Copyright
Copyright © Materials Research Society 2009

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