AFM STUDY OF THE INTERACTIONS BETWEEN

SYNOVIAL LIQUID’S MOLECULAR COMPONENTS IN BOUNDARY LUBRICATION

D.A. Mirea, A-M. Trunfio-Sfarghiu, A. Piednoir, J.P. Rieu, M.G. Blanchin, Y. Berthier

RoTrib’10Iaşi, România

The Synovial Joints

Most joints are freely moveable.They allow different movement, depending on the

shape of the bones meeting in that joint.The shoulder, hip and ankle are susceptible to

injury due to the amount of movement possible at them

The Synovial Fluid

A non-Newtonian fluid found in the cavities of synovial joints

Its principal role is to reduce friction inside the synovial joints during movement

The resorbtion of the synovial fluid can’t be treated. The only option offered by the medicine is the total replacement of the joint.

Highly important! Discovering the components that may be used in developing an artificial synovial liquid.

Lipid bilayers

Synovial gelAlbumin

Hyaluronic acid

Glucydic component:

Hyaluronic acid

Hydrophile glucides, L ~ 12

000 nm

Proteic component:

Albumin + Globulin

Globular proteins

8 nm3 nm

+

Lipids

2.5 nm

0,5 nm

+

Glicoproteic component:

Proteo-glycan (PG4-lubricin-SZP)

Volume

Interface

Which molecule is deficitary in

this model?

The synovial model

Adopted strategy

Adhesion force measurements using the “Force Measurement” mode on the AFM microscope

5 nm

Lipid bilayer

Globular proteins

8 nm3 nm Hydrophile

glucides, L ~ 12 000 nm

Proteo-glycan

Atomic Force Microscopy – Mode Force Measurements

Atomic Force Microscopy is being used mostly for imaging, although the AFM is a very suitable tool for force measurements.

Preparing the experiment

AFM cantilevers

AFM glass supports Lipid bilayers

Polysaccharides

CMA

Albumin (BSA)

γ-Globulin

Preoteo-glycan

Experimental Protocol

The lipid bilayers

2 mM Ca++

2 incubations

20 mM micelles 1 mol lipide / 6 mol DDM

Slow dilution

5 nm

The co-absorbtion of lipid micells and detergent was used to obtain the lipid bilayers

ResultsThe CMA test

ResultsThe glycoproteic

component

Results The proteic component - Albumin

ResultsThe proteic component - γ-

Globulin

ResultsThe glucidic

component

Without penetration With penetration

Conclusions & interpretation

PG4Cartilage

Hyaluronic acid + seric

proteins

Lipid layers

Presence of lipid

multilamelar layers

Hills A.B., Internal

Medicine Journal 2002

Hyaluronic acid (AH)A high affinity for the lipid

bilayersSeric proteins – low adhesion rates but

reticular with AH (Oates K.M.N. J. R. Soc. Interface,

2005)

AH aids in creating the

vesicles. AH and the seric

proteins remain inside the vesicles

PG4~lubricin~SZPA high rate of adhesion

onto lipid bilayers - Ineractions with the CS

groups from the articular cartilage (Rhee

D.K., The Journal of Clinical Investigation, 2005)

PG4 aids in fixing the lipid layers on the

cartilage

Presence of lipid multilamelar vesicles

Trunfio-Sfarghiu A.M, and all.

BiomMedD'2008

0.2 µm

Conclusions & interpretation

Hyaluronic acid + seric proteins

Lipid bilayers

PGCartilageLipid layers

proteins + glucids Lipid bilayers

2 µm

Discontinuous structure of synovial liquid the hydrodynamic theories do not apply

Sliding location betwwen lipid bilayers c.f = 0.0015 (Trunfio-Sfarghiu A.M., Tribology International 2007)

Thank you for your attention!