title: Poroelasticity of cartilage at the nanoscale.
abstract: Atomic-force-microscopy-based oscillatory loading was used in conjunction with finite element modeling to quantify and predict the frequency-dependent mechanical properties of the superficial zone of young bovine articular cartilage at deformation amplitudes, δ, of ~15 nm; i.e., at macromolecular length scales. Using a spherical probe tip (R ~ 12.5 μm), the magnitude of the dynamic complex indentation modulus, |E*|, and phase angle, φ, between the force and tip displacement sinusoids, were measured in the frequency range f ~ 0.2-130 Hz at an offset indentation depth of δ(0) ~ 3 μm. The experimentally measured |E*| and φ corresponded well with that predicted by a fibril-reinforced poroelastic model over a three-decade frequency range. The peak frequency of phase angle, f(peak), was observed to scale linearly with the inverse square of the contact distance between probe tip and cartilage, 1/d(2), as predicted by linear poroelasticity theory. The dynamic mechanical properties were observed to be independent of the deformation amplitude in the range δ = 7-50 nm. Hence, these results suggest that poroelasticity was the dominant mechanism underlying the frequency-dependent mechanical behavior observed at these nanoscale deformations. These findings enable ongoing investigations of the nanoscale progression of matrix pathology in tissue-level disease.
authors: Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
authors: Hadi Tavakoli
authors: HT
authors: Nia
authors: Lin
authors: L
authors: Han
authors: Yang
authors: Y
authors: Li
authors: Christine
authors: C
authors: Ortiz
authors: Alan
authors: A
authors: Grodzinsky
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology; D002356:Cartilage / Q000502:physiology*; D002417:Cattle; D016001:Confidence Intervals; D055119:Elastic Modulus / Q000502:physiology; D004548:Elasticity; D005109:Extracellular Matrix / Q000378:metabolism; D008954:Models, Biological; D053758:Nanoparticles / Q000737:chemistry*; D010329:Patella / Q000378:metabolism; D016062:Porosity; D011312:Pressure; D012212:Rheology