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Lateral nanomechanics of cartilage aggrecan macromolecules
Journal article   Open access   Peer reviewed

Lateral nanomechanics of cartilage aggrecan macromolecules

Lin Han, Delphine Dean, Christine Ortiz and Alan J Grodzinsky
Biophysical journal, v 92(4), pp 1384-1398
15 Feb 2007
DOI: https://doi.org/10.1529/biophysj.106.091397
PMID: 17142289
Featured in Collection :   UN Sustainable Development Goals @ Drexel
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https://doi.org/10.1529/biophysj.106.091397View
Published, Version of Record (VoR)Open Access (Publisher-Specific),  Open

Abstract

Aggrecans - chemistry Animals Biomechanical Phenomena Cartilage, Articular - chemistry Cattle Macromolecular Substances Microscopy, Atomic Force Models, Biological Nanotechnology Viscosity
To explore the role of the brush-like proteoglycan, aggrecan, in the shear behavior of cartilage tissue, we measured the lateral resistance to deformation of a monolayer of chemically end-attached cartilage aggrecan on a microcontact printed surface in aqueous NaCl solutions via lateral force microscopy. The effects of bath ionic strength (IS, 0.001-1.0 M) and lateral displacement rate (approximately 1-100 microm/s) were studied using probe tips functionalized with neutral hydroxyl-terminated self-assembled alkanethiol monolayers. Probe tips having two different end-radii (R approximately 50 nm and 2.5 microm) enabled access to different length-scales of interactions (nano and micro). The measured lateral force was observed to depend linearly on the applied normal force, and the lateral force to normal force proportionality constant, mu, was calculated. The value mu increased (from 0.03 +/- 0.01 to 0.11 +/- 0.01) with increasing bath IS (0.001-1.0 M) for experiments using the microsized tip due to the larger compressive strain of aggrecan that resulted from increased IS at constant compressive force. With the nanosized tip, mu also increased with IS but by a smaller amount due to the fewer number of aggrecan involved in shear deformation. The variations in lateral force as a function of applied compressive strain epsilon(n) and changes in bath IS suggested that both electrostatic and nonelectrostatic interactions contributed significantly to the shear deformational behavior of the aggrecan layers. While lateral force did not vary with lateral displacement rate at low IS, where elastic-like electrostatic interactions between aggrecan dominated, lateral force increased significantly with displacement rate at physiological and higher IS, suggestive of additional viscoelastic and/or poroelastic interactions within the aggrecan layer. These data provide insights into molecular-level deformation of aggrecan macromolecules that are important to the understanding of cartilage behavior.

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Web of Science research areas
Biophysics
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