Nanoindentation of Histological Specimens using an Extension of the Oliver and Pharr Method

Abstract

The micro-mechanical properties of 5 μm thick histological sections of ferret aorta and vena cava were mapped as a function of distance from the outer adventitial layer using nanoindentation. In order to decouple the effect of the glass substrate on the elastic modulus of these thin sections, the nanoindentation data were analyzed using the extended Oliver and Pharr method which is readily accessible for coatings and layered materials with the software package, FilmDoctor®. In the aorta, the elastic modulus was found to decrease progressively from 35 MPa at the adventitia (outermost layer) to 8 MPa at the intima (innermost layer). This decrease in modulus was inversely correlated with elastic fibre density. In contrast, in the vena cava, the stiffest regions were found to be the adventitial (outer) and intimal (innermost) sections of the vessel cross-section. Both these regions were enriched in ECM components. The central region, thought to be largely cellular, had a relatively constant modulus of around 20 MPa. This study demonstrates that with this methodology it is possible to distinguish micro-mechanically between large arteries and veins, and therefore the same approach should allow age or disease related changes in the mechanical properties within a tissue to be quantified.

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

“…To overcome these limitations, this work demonstrates how the extended Oliver–Pharr method for thin coating analysis27 can be used to obtain valuable micromechanical data for soft tissue, following nanoindentation of thin tissue sections with a conventional methodology. An earlier version of this work was presented at the 2008 MRS Spring meeting, San Francisco28; here we report a more complete analysis of the correlation between histology and mechanical properties.…”

Mapping the Micromechanical Properties of Cryo-sectioned Aortic Tissue with Scanning Acoustic Microscopy

“…[6]. The outer (adventitial) layer is known to be relatively acellular and rich in collagen, the stiffest component of large blood vessels.…”

“…We have recently used a nanoindentation analysis methodology to spatially map the mechanical properties of 5 μm thick ferret aorta and vena cava, and related the micromechanical properties to the histological distribution of elastic fibres [6]. In this study, we use SAM to quantify variations in ferret aorta mechanical properties at a length scale of around 10 -6 m. SAM is a unique, high spatial resolution tool for the study of mechanical properties of biological tissue, potentially allowing a direct correlation between histology and micromechanical properties of tissue.…”

An investigation of scratch testing of silicone elastomer coatings with a thickness gradient

“…It is beyond the scope of this article to repeat the structural basics of the model or to demonstrate its application for multi‐axial contact simulations or the method of extracting true coating parameters. Thus, the reader is referred to a variety of references published together with Pharr, Bemporad, Derby, Griepentrog, Chudoba, Richter and many others 6, 32–44. Among these are: determination of yield strength of homogeneous materials via nanoindentation with sharp indenters30, 45 determination of true Young's modulus and yield strength of “standard” coating materials via nanoindentation with sharp indenters32–37 determination of true Young's modulus and yield strength of coating materials of ultra thin coatings with thicknesses well below 100 nm via nanoindentation with sharp indenters38, 39 determination of true Young's modulus and yield strength of unusual or tricky coating materials via nanoindentation with sharp indenters6, 41–44 determination of true Young's modulus, yield strength, and residual stresses of coating materials via nanoindentation with sharp indenters 23…”

“…determination of true Young's modulus and yield strength of unusual or tricky coating materials via nanoindentation with sharp indenters6, 41–44…”