Nanomechanics of cartilage extracellular matrix macromolecules

In this thesis, the shear and self-adhesion nanomechanical properties between opposing cartilage aggrecan macromolecules were probed. In addition, nanoscale dynamic oscillatory mechanical properties of cartilage and its type II collagen network was measured. Aggrecan shear nanomechanics was assessed via microcontact printing and lateral force microscopy. Lateral force between aggrecan and the probe tip, and compression of aggrecan was simultaneously measured in 0.001 - 1.0 M NaCl aqueous solutions. Using the microsized tip (Rtip ~ 2.5 [mu]m) enabled a large assembly of ~ 103 aggrecan molecules to interact simultaneously, closely mimicking the in vivo conditions.Both electrostatic and nonelectrostatic components were identified to importantly contribute to aggrecan shear. At near physiological IS (0.1 M), significant rate dependence was observed, suggestive of visco/poroelastic interactions within the aggrecan layer. By using an aggrecan end-functionalized colloidal tip, shear of two opposing aggrecan layers was assessed in a similar fashion. Lower lateral force and a more marked rate dependence were measured compared to the shear of a single layer, due to the aggrecan inter-layer molecular interpenetration and the different local z-dependent charge density distribution. The addition of Ca2+, at physiological-like 2 mM concentration, significantly affects cartilage shear by its electrostatic screening and binding effects. Marked aggrecan self-adhesion upon separation was discovered after static compression in the presence of electrostatic repulsion in physiological-like conditions.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Materials Science and Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2007

Author dc:creator

• Han, Lin, Ph. D. Massachusetts Institute of Technology

Advisor dc:contributor.advisor

• Alan J. Grodzinsky and Christine Ortiz.

• Materials Science and Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/42134

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/42134