This study aimed to characterize the in-situ mechanical property and morphology of
individual collagen fibril in osteoarthritic (OA) cartilage using indentation-type
atomic force microscopy (IT-AFM). The specimens with intact articular cartilage
(AC), mild to severe degenerated OA cartilage were collected with informed consent
from the postmenopausal women who underwent hip or knee arthroplasty. The fresh
specimens were cryo-sectioned by layers with 50m thick for each from the articular
surface to calcified cartilage, and then processed for AFM imaging and
nanoindentation test. For each layer, a total of twenty collagen fibrils were randomly
selected for testing. AFM tips with the nominal radius less than 10 nm were employed
for probing the individual collagen fibril, and the obtained cantilever deflection signal
and displacement were recorded for calculating its elastic modulus. Besides AFM
nanoindentation, AFM and scanning electron microscopy (SEM) images,
haematoxylin & eosin (H&E) staining and micro-indentation were performed on AC
to study the changes of ultrastructure and composition between intact AC and OA
cartilage. Results showed that an intact AC exhibited a gradation in elastic modulus of
collagen fibrils from surface region (2.65±0.31GPa) to bottom region (3.70±0.44GPa).
It was noted in the initial stage of OA cartilage that the coefficient of variation for
mechanical properties of collagen fibers, ranging from 25~48%, significantly
increased as compared with intact one (12%). The thickened and stiffened collagen
fibrils initially occurred at either surface region (3.11±0.91GPa) or bottom region
(5.64±1.10GPa) with OA progression. Besides thickens, alteration of D-periodic
banding patterns of collagen fibrils was observed. It was echoed by fibrotic changes
of surface region and tidemark irregularities. On the contrast, the micromechanical
properties of cartilage decreased while AC suffered from OA. This result revealed the
different approachs of nano and micro-mechanical properties changes in AC. In
summary, the alteration of mechanical properties of collagen fibrils started from
calcified cartilage as well as articular surface during OA onset, and the low
compliance of thickened collagen fibrils deteriorated along disease progression. This
study also reveals that the outstanding ability by AFM, in investigating the structure
and mechanical properties of collagen fibrils and AC in nanometer scale, is
impressive and this nanotechnological instrument is worth to be expected in further
development for clinical use. / published_or_final_version / Mechanical Engineering / Master / Master of Philosophy
| Identifer | oai:union.ndltd.org:HKU/oai:hub.hku.hk:10722/174379 |
| Date | January 2011 |
| Creators | Wu, Cheuk-bun, Benny., 胡卓斌. |
| Contributors | Tang, B, Lu, WW |
| Publisher | The University of Hong Kong (Pokfulam, Hong Kong) |
| Source Sets | Hong Kong University Theses |
| Language | English |
| Detected Language | English |
| Type | PG_Thesis |
| Source | http://hub.hku.hk/bib/B4732210X |
| Rights | The author retains all proprietary rights, (such as patent rights) and the right to use in future works., Creative Commons: Attribution 3.0 Hong Kong License |
| Relation | HKU Theses Online (HKUTO) |
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