Nanomechanical Mapping of Hard Tissues by Atomic Force Microscopy: An Application to Cortical Bone

Marco Bontempi, Francesca Salamanna, Rosario Capozza, Andrea Visani, Milena Fini, Alessandro Gambardella*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Force mapping of biological tissues via atomic force microscopy (AFM) probes the mechanical properties of samples within a given topography, revealing the interplay between tissue organization and nanometer-level composition. Despite considerable attention to soft biological samples, constructing elasticity maps on hard tissues is not routine for standard AFM equipment due to the difficulty of interpreting nanoindentation data in light of the available models of surface deformation. To tackle this issue, we proposed a protocol to construct elasticity maps of surfaces up to several GPa in moduli by AFM nanoindentation using standard experimental conditions (air operation, nanometrically sharp spherical tips, and cantilever stiffness below 30 N/m). We showed how to process both elastic and inelastic sample deformations simultaneously and independently and quantify the degree of elasticity of the sample to decide which regime is more suitable for moduli calculation. Afterwards, we used the frequency distributions of Young’s moduli to quantitatively assess differences between sample regions different for structure and composition, and to evaluate the presence of mechanical inhomogeneities. We tested our method on histological sections of sheep cortical bone, measuring the mechanical response of different osseous districts, and mapped the surface down to the single collagen fibril level.
Original languageEnglish
Article number7512
Number of pages14
JournalMaterials
Volume15
Issue number21
Early online date26 Oct 2022
DOIs
Publication statusPublished - 1 Nov 2022

Keywords

  • nanomechanical mapping
  • atomic force microscopy
  • force mapping
  • tissue nanoindentation
  • nano biomechanics
  • biomaterials
  • cortical bone
  • elasticity

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