Using atomic force microscopy, we quantified the micro-mechanical properties, including both the Young's modulus from indentation curves and viscosity coefficient from creep curves, of relatively intact metastatic breast tumours and their surrounding bone microenvironment isolated from mice (as outlined in the fluorescent image) under near physiological conditions, and compared with other breast cancer models both ex vivo and in vitro. A mechanical distribution of extremely low elastic modulus and viscosity was identified on metastatic tumours, which were significantly more compliant than both 2D in vitro cultured cancer cells and subcutaneous tumour explants.

Simultaneously obtained AFM maps from the cortical bone under near physiological conditions, including maps of (left) topography, (middle) measured elastic moduli and (right) calculated viscosity. Both elastic and viscoelastic properties are found to be highly heterogeneous with moduli ranging over 3 to 5 orders of magnitude. In contrast to common understanding, the cortical bone also includes extremely compliant areas, with moduli of a few Pascal and viscosities as low as tens Pa·s. 

Using our NanoTest Vantage nanoindenter, specific domains within a cement-based material, as indicated in the optical images, can be precisely targeted. The resulting load vs. indentation depth curves, shown in the inset, allow us to measure the hardness and reduced modulus of these targeted areas.